sample PW tests

* develop: (174 commits)
  chore: cleanup
  fix: Error type
  chore: Bump node
  Show good error messages.
  chore: fix trailing slash
  chore(deps): update all non-major dependencies
  Block only tests
  snapshot
  Remove it.only
  fix #1103
  chore(deps): update all non-major dependencies
  Update Browserslist
  chore: Update deps
  fix: Remove AsyncQueue
  Update Browserslist
  Fix #1089: Update monaco-mermaid
  chore(deps): update all non-major dependencies
  fix lint
  chore: Cleanup, fix theme
  fix: Snapshot, env types
  ...

.eslintrc.cjs

@@ -5,9 +5,10 @@ module.exports = {
     'eslint:recommended',
     'plugin:@typescript-eslint/recommended',
     // 'plugin:@typescript-eslint/recommended-requiring-type-checking',
+    'plugin:@typescript-eslint/strict',
     'prettier'
   ],
-  plugins: ['svelte3', 'tailwindcss', '@typescript-eslint', 'es', 'vitest'],
+  plugins: ['svelte3', 'tailwindcss', '@typescript-eslint', 'es', 'vitest', 'no-only-tests'],
   ignorePatterns: [
     'docs/*',
     '*.cjs',
@@ -19,7 +20,19 @@ module.exports = {
     'package.json',
     'tsconfig.json'
   ],
-  overrides: [{ files: ['*.svelte'], processor: 'svelte3/svelte3' }],
+  overrides: [
+    { files: ['*.svelte'], processor: 'svelte3/svelte3' },
+    {
+      files: ['*.ts'],
+      extends: [
+        'eslint:recommended',
+        'plugin:@typescript-eslint/recommended',
+        'plugin:@typescript-eslint/recommended-requiring-type-checking',
+        'plugin:@typescript-eslint/strict',
+        'prettier'
+      ]
+    }
+  ],
   settings: {
     'svelte3/typescript': () => require('typescript')
   },
@@ -45,6 +58,7 @@ module.exports = {
     '@typescript-eslint/no-unsafe-member-access': 'off',
     '@typescript-eslint/no-unsafe-assignment': 'off',
     'es/no-regexp-lookbehind-assertions': 'error',
-    curly: ['error', 'all']
+    curly: ['error', 'all'],
+    'no-only-tests/no-only-tests': 'error'
   }
 };

.github/workflows/deploy.yml

@@ -16,7 +16,7 @@ jobs:
 
       - uses: actions/setup-node@v3
         with:
-          node-version: '16'
+          node-version: 18
           cache: yarn
 
       - name: Build & Deploy

.github/workflows/playwright.yml

@@ -0,0 +1,27 @@
+name: Playwright Tests
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ main, master ]
+jobs:
+  test:
+    timeout-minutes: 60
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-node@v2
+      with:
+        node-version: '14.x'
+    - name: Install dependencies
+      run: yarn
+    - name: Install Playwright Browsers
+      run: npx playwright install --with-deps
+    - name: Run Playwright tests
+      run: yarn playwright test
+    - uses: actions/upload-artifact@v2
+      if: always()
+      with:
+        name: playwright-report
+        path: playwright-report/
+        retention-days: 30

.github/workflows/tests.yml

@@ -32,7 +32,7 @@ jobs:
 
       - uses: actions/setup-node@v3
         with:
-          node-version: 16
+          node-version: 18
           cache: 'yarn'
 
       # Install NPM dependencies, cache them correctly

.github/workflows/unit-tests.yml

@@ -26,7 +26,7 @@ jobs:
 
       - uses: actions/setup-node@v3
         with:
-          node-version: 16
+          node-version: 18
           cache: 'yarn'
 
       - name: Lint & Test

.gitignore

@@ -12,3 +12,6 @@ yarn-error.log
 /cypress/downloads
 /cypress/videos
 /cypress/screenshots
+/test-results/
+/playwright-report/
+/playwright/.cache/

.vscode/settings.json

@@ -1,6 +1,6 @@
 {
   "editor.formatOnSave": true,
-  "cSpell.words": ["asyncable", "mindmap", "pako", "Serde", "serdes"],
+  "cSpell.words": ["asyncable", "KROKI", "mindmap", "pako", "Serde", "serdes", "tailwindcss"],
   "vitest.commandLine": "yarn test:unit",
   "vitest.enable": true,
   "testing.autoRun.mode": "rerun",

Dockerfile

@@ -6,7 +6,7 @@
 # Stop               : press ctrl + c 
 #                                     or 
 #                                        docker stop mermaid-live-editor
-FROM node:18.12.0 as mermaid-live-editor-builder 
+FROM node:18.12.1 as mermaid-live-editor-builder 
 COPY --chown=node:node . /home
 WORKDIR /home
 RUN yarn install

cypress/e2e/diagramUpdate.spec.ts

@@ -69,6 +69,14 @@ describe('Auto sync tests', () => {
       )
       .should('exist');
   });
+
+  it('should update diagram after entire text is removed', () => {
+    // https://github.com/mermaid-js/mermaid-live-editor/issues/1102
+    getEditor().type(`${cmd} a {backspace}`);
+    getEditor().type('graph LR');
+    getEditor().type(' {enter}  A-->Car');
+    cy.get('#view').contains('Car').should('exist');
+  });
 });
 
 describe('Pan and Zoom', () => {

cypress/e2e/util.ts

@@ -17,6 +17,7 @@ export const verifyFileSize = (
 ) => {
   const fileName = `mermaid-${fileType}-2022-01-01-000000.${extension}`;
   const filePath = `${downloadsFolder}/${fileName}`;
+  // eslint-disable-next-line @typescript-eslint/no-unsafe-call
   cy.verifyDownload(fileName);
   cy.readFile(filePath, null, {
     log: false
@@ -31,6 +32,7 @@ export const verifyFileSnapshot = (
 ) => {
   const fileName = `mermaid-${fileType}-2022-01-01-000000.${extension}`;
   const filePath = `${downloadsFolder}/${fileName}`;
+  // eslint-disable-next-line @typescript-eslint/no-unsafe-call
   cy.verifyDownload(fileName);
   cy.readFile(filePath, null, {
     log: false

cypress/snapshots.js

@@ -16,7 +16,7 @@ module.exports = {
       "1": "{\"code\":\"graph TD\\n    A[Party] -->|Get money| B(Go shopping!!)\\n    \",\"mermaid\":\"{\\n  \\\"theme\\\": \\\"forest\\\",\\n  \\\"test\\\": \\\"hello world\\\"\\n}\",\"autoSync\":true,\"updateDiagram\":true,\"loader\":{\"type\":\"files\",\"config\":{\"codeURL\":\"https://gist.githubusercontent.com/sidharthv96/6268a23e673a533dcb198f241fd7012a/raw/4eb03887e6a41397e80bdcdbf94017c498f8f1e2/code.mmd\",\"configURL\":\"https://gist.githubusercontent.com/sidharthv96/6268a23e673a533dcb198f241fd7012a/raw/4eb03887e6a41397e80bdcdbf94017c498f8f1e2/config.json\"}}}"
     }
   },
-  "__version": "10.10.0",
+  "__version": "11.2.0",
   "Auto sync tests": {
     "should dim diagram when code is edited": {
       "1": "{\"code\":\"graph TD\\n    A[Christmas] -->|Get money| B(Go shopping)\\n    B --> C{Let me think}\\n    C -->|One| D[Laptop]\\n    C -->|Two| E[iPhone]\\n    C -->|Three| F[fa:fa-car Car]\\n    C --> Test\",\"mermaid\":\"{\\n  \\\"theme\\\": \\\"default\\\"\\n}\",\"autoSync\":false,\"updateDiagram\":false}"

package.json

@@ -19,61 +19,65 @@
     "test:coverage": "vitest run --coverage",
     "test:browser": "cypress run",
     "test": "test:unit && test:browser",
-    "cy": "cypress open"
+    "cy": "cypress open",
+    "pw": "npx playwright test"
   },
   "devDependencies": {
     "@cypress/snapshot": "2.1.7",
-    "@sveltejs/adapter-static": "1.0.0-next.46",
+    "@playwright/test": "^1.28.1",
-    "@sveltejs/kit": "1.0.0-next.522",
+    "@sveltejs/adapter-static": "1.0.0-next.48",
+    "@sveltejs/kit": "1.0.0-next.561",
     "@testing-library/jest-dom": "5.16.5",
     "@testing-library/svelte": "3.2.2",
     "@types/pako": "2.0.0",
     "@types/uuid": "8.3.4",
-    "@typescript-eslint/eslint-plugin": "5.42.0",
+    "@typescript-eslint/eslint-plugin": "5.44.0",
-    "@typescript-eslint/parser": "5.42.0",
+    "@typescript-eslint/parser": "5.44.0",
-    "@vitest/ui": "0.25.1",
+    "@vitest/ui": "^0.25.3",
-    "autoprefixer": "10.4.12",
+    "autoprefixer": "^10.4.13",
     "c8": "7.12.0",
-    "chai": "4.3.6",
+    "chai": "^4.3.7",
-    "cssnano": "5.1.13",
+    "cssnano": "^5.1.14",
     "cy-verify-downloads": "0.1.11",
-    "cypress": "11.0.1",
+    "cypress": "11.2.0",
     "cypress-localstorage-commands": "2.2.1",
-    "eslint": "8.27.0",
+    "eslint": "8.28.0",
     "eslint-config-prettier": "8.5.0",
     "eslint-plugin-cypress": "2.12.1",
     "eslint-plugin-es": "4.1.0",
+    "eslint-plugin-no-only-tests": "^3.1.0",
     "eslint-plugin-postcss-modules": "2.0.0",
     "eslint-plugin-svelte3": "4.0.0",
-    "eslint-plugin-tailwindcss": "3.6.2",
+    "eslint-plugin-tailwindcss": "3.7.0",
-    "eslint-plugin-vitest": "0.0.11",
+    "eslint-plugin-vitest": "^0.0.20",
-    "esserializer": "1.3.2",
+    "esserializer": "1.3.5",
-    "husky": "8.0.1",
+    "font-awesome": "^4.7.0",
-    "jsdom": "20.0.1",
+    "husky": "^8.0.2",
+    "jsdom": "20.0.3",
     "lint-staged": "13.0.3",
-    "node-html-parser": "6.1.1",
+    "node-html-parser": "^6.1.4",
-    "postcss": "8.4.18",
+    "postcss": "^8.4.19",
     "postcss-load-config": "4.0.1",
-    "prettier": "2.7.1",
+    "prettier": "2.8.0",
-    "prettier-plugin-svelte": "2.8.0",
+    "prettier-plugin-svelte": "^2.8.1",
     "svelte": "3.53.1",
     "svelte-preprocess": "4.10.7",
-    "tailwindcss": "3.2.1",
+    "tailwindcss": "^3.2.4",
-    "tslib": "2.4.0",
+    "tslib": "^2.4.1",
-    "typescript": "4.8.4",
+    "typescript": "4.9.3",
-    "vite": "3.2.2",
+    "vite": "^3.2.4",
-    "vitest": "0.25.1"
+    "vitest": "^0.25.3"
   },
   "dependencies": {
     "@mermaid-js/mermaid-mindmap": "9.2.2",
     "analytics": "0.8.1",
     "analytics-plugin-plausible": "0.0.6",
-    "daisyui": "2.39.1",
+    "daisyui": "2.42.1",
-    "js-base64": "3.7.2",
+    "js-base64": "3.7.3",
     "mermaid": "9.2.2",
     "moment": "2.29.4",
     "monaco-editor": "0.34.1",
-    "monaco-mermaid": "1.0.6",
+    "monaco-mermaid": "1.0.8",
     "pako": "2.1.0",
     "random-word-slugs": "0.1.6",
     "svg-pan-zoom": "3.6.1",
@@ -86,7 +90,7 @@
     ]
   },
   "volta": {
-    "node": "18.12.0",
+    "node": "18.12.1",
     "yarn": "1.22.19"
   },
   "engines": {

playwright.config.ts

@@ -0,0 +1,106 @@
+import type { PlaywrightTestConfig } from '@playwright/test';
+import { devices } from '@playwright/test';
+
+/**
+ * Read environment variables from file.
+ * https://github.com/motdotla/dotenv
+ */
+// require('dotenv').config();
+
+/**
+ * See https://playwright.dev/docs/test-configuration.
+ */
+const config: PlaywrightTestConfig = {
+  testDir: './tests',
+  /* Maximum time one test can run for. */
+  timeout: 30 * 1000,
+  expect: {
+    /**
+     * Maximum time expect() should wait for the condition to be met.
+     * For example in `await expect(locator).toHaveText();`
+     */
+    timeout: 5000
+  },
+  /* Run tests in files in parallel */
+  fullyParallel: true,
+  /* Fail the build on CI if you accidentally left test.only in the source code. */
+  forbidOnly: !!process.env.CI,
+  /* Retry on CI only */
+  retries: process.env.CI ? 2 : 0,
+  /* Opt out of parallel tests on CI. */
+  workers: process.env.CI ? 1 : undefined,
+  /* Reporter to use. See https://playwright.dev/docs/test-reporters */
+  reporter: 'html',
+  /* Shared settings for all the projects below. See https://playwright.dev/docs/api/class-testoptions. */
+  use: {
+    /* Maximum time each action such as `click()` can take. Defaults to 0 (no limit). */
+    actionTimeout: 0,
+    /* Base URL to use in actions like `await page.goto('/')`. */
+    baseURL: 'http://localhost:3000',
+    /* Collect trace when retrying the failed test. See https://playwright.dev/docs/trace-viewer */
+    trace: 'on-first-retry'
+  },
+
+  /* Configure projects for major browsers */
+  projects: [
+    {
+      name: 'chromium',
+      use: {
+        ...devices['Desktop Chrome']
+      }
+    }
+
+    // {
+    //   name: 'firefox',
+    //   use: {
+    //     ...devices['Desktop Firefox'],
+    //   },
+    // },
+
+    // {
+    //   name: 'webkit',
+    //   use: {
+    //     ...devices['Desktop Safari'],
+    //   },
+    // },
+
+    /* Test against mobile viewports. */
+    // {
+    //   name: 'Mobile Chrome',
+    //   use: {
+    //     ...devices['Pixel 5'],
+    //   },
+    // },
+    // {
+    //   name: 'Mobile Safari',
+    //   use: {
+    //     ...devices['iPhone 12'],
+    //   },
+    // },
+
+    /* Test against branded browsers. */
+    // {
+    //   name: 'Microsoft Edge',
+    //   use: {
+    //     channel: 'msedge',
+    //   },
+    // },
+    // {
+    //   name: 'Google Chrome',
+    //   use: {
+    //     channel: 'chrome',
+    //   },
+    // },
+  ]
+
+  /* Folder for test artifacts such as screenshots, videos, traces, etc. */
+  // outputDir: 'test-results/',
+
+  /* Run your local dev server before starting the tests */
+  // webServer: {
+  //   command: 'npm run start',
+  //   port: 3000,
+  // },
+};
+
+export default config;

src/app.html

@@ -17,8 +17,8 @@
     <link rel="manifest" href="%sveltekit.assets%/manifest.json" />
     <link
       rel="stylesheet"
-      href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.2.0/css/all.min.css"
+      href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.2.1/css/all.min.css"
-      integrity="sha512-xh6O/CkQoPOWDdYTDqeRdPCVd1SpvCA9XXcUnZS2FmJNp1coAFzvtCN9BmamE+4aHK8yyUHUSCcJHgXloTyT2A=="
+      integrity="sha512-MV7K8+y+gLIBoVD59lQIYicR65iaqukzvf/nwasF0nqhPay5w/9lJmVM2hMDcnK1OnMGCdVK+iQrJ7lzPJQd1w=="
       crossorigin="anonymous"
       referrerpolicy="no-referrer" />
     <link

src/env.d.ts

@@ -1,11 +1,11 @@
 /// <reference types="vite/client" />
 
 interface ImportMetaEnv {
-  readonly MERMAID_RENDERER_URL: string;
+  readonly MERMAID_RENDERER_URL?: string;
-  readonly MERMAID_KROKI_RENDERER_URL: string;
+  readonly MERMAID_KROKI_RENDERER_URL?: string;
-  readonly MERMAID_CDN_URL: string;
+  readonly MERMAID_CDN_URL?: string;
-  readonly MERMAID_BASE_URL: string;
+  readonly MERMAID_BASE_URL?: string;
-  readonly MERMAID_LOCAL: boolean;
+  readonly MERMAID_LOCAL?: boolean;
   // more env variables...
 }
 

src/global.d.ts

@@ -9,7 +9,8 @@ declare global {
   namespace jest {
     interface Matchers<R = void>
       // eslint-disable-next-line @typescript-eslint/ban-ts-comment
-      // @ts-ignore
+      // @ts-expect-error
+      // eslint-disable-next-line no-undef
       extends TestingLibraryMatchers<typeof expect.stringContaining, R> {}
   }
 }

src/lib/components/Actions.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
   import { browser } from '$app/environment';
-  import Card from '$lib/components/card/card.svelte';
+  import Card from '$lib/components/Card/Card.svelte';
   import { env } from '$lib/util/env';
   import { pakoSerde } from '$lib/util/serde';
   import { stateStore } from '$lib/util/state';
@@ -15,8 +15,8 @@
     `mermaid-diagram-${moment().format('YYYY-MM-DD-HHmmss')}.${ext}`;
 
   const getBase64SVG = (svg?: HTMLElement, width?: number, height?: number): string => {
-    svg?.setAttribute('height', `${height}px`);
+    height && svg?.setAttribute('height', `${height}px`);
-    svg?.setAttribute('width', `${width}px`); // Workaround https://stackoverflow.com/questions/28690643/firefox-error-rendering-an-svg-image-to-html5-canvas-with-drawimage
+    width && svg?.setAttribute('width', `${width}px`); // Workaround https://stackoverflow.com/questions/28690643/firefox-error-rendering-an-svg-image-to-html5-canvas-with-drawimage
     if (!svg) {
       svg = getSvgEl();
     }
@@ -28,7 +28,10 @@
 
   const exportImage = (event: Event, exporter: Exporter) => {
     const canvas: HTMLCanvasElement = document.createElement('canvas');
-    const svg: HTMLElement = document.querySelector('#container svg');
+    const svg: HTMLElement | null = document.querySelector('#container svg');
+    if (!svg) {
+      throw new Error('svg not found');
+    }
     const box: DOMRect = svg.getBoundingClientRect();
     canvas.width = box.width;
     canvas.height = box.height;
@@ -43,6 +46,9 @@
     }
 
     const context = canvas.getContext('2d');
+    if (!context) {
+      throw new Error('context not found');
+    }
     context.fillStyle = 'white';
     context.fillRect(0, 0, canvas.width, canvas.height);
 
@@ -56,12 +62,12 @@
 
   const getSvgEl = () => {
     const svgEl: HTMLElement = document
-      .querySelector('#container svg')
+      .querySelector('#container svg')!
       .cloneNode(true) as HTMLElement;
     svgEl.setAttribute('xmlns:xlink', 'http://www.w3.org/1999/xlink');
     const fontAwesomeCdnUrl = Array.from(document.head.getElementsByTagName('link'))
       .map((l) => l.href)
-      .find((h) => h && h.includes('font-awesome'));
+      .find((h) => h.includes('font-awesome'));
     if (fontAwesomeCdnUrl == null) {
       return svgEl;
     }
@@ -99,10 +105,10 @@
       context.drawImage(image, 0, 0, canvas.width, canvas.height);
       canvas.toBlob((blob) => {
         try {
-          // @ts-ignore: https://github.com/microsoft/TypeScript-DOM-lib-generator/pull/1004/files
+          if (!blob) {
+            throw new Error('blob is empty');
+          }
           void navigator.clipboard.write([
-            /* eslint-disable no-undef */
-            // @ts-ignore: https://github.com/microsoft/TypeScript/issues/43821
             new ClipboardItem({
               [blob.type]: blob
             })
@@ -142,7 +148,7 @@
   let gistURL = '';
   stateStore.subscribe(({ loader }) => {
     if (loader?.type === 'gist') {
-      // @ts-ignore Gist will have url
+      // @ts-expect-error Gist will have url
       gistURL = loader.config.url;
     }
   });
@@ -166,8 +172,7 @@
   if (browser && ['mermaid.live', 'netlify'].some((path) => window.location.host.includes(path))) {
     isNetlify = true;
   }
-  stateStore.subscribe(async (state) => {
+  stateStore.subscribe(({ code, serialized }) => {
-    const { code, serialized } = await state;
     iUrl = `${rendererUrl}/img/${serialized}?type=png`;
     svgUrl = `${rendererUrl}/svg/${serialized}`;
     krokiUrl = `${krokiRendererUrl}/mermaid/svg/${pakoSerde.serialize(code)}`;

src/lib/components/Card/Card.svelte

@@ -1,11 +1,11 @@
 <script lang="ts">
   import type { Tab } from '$lib/types';
   import { slide } from 'svelte/transition';
-  import Tabs from './tabs.svelte';
+  import Tabs from './Tabs.svelte';
   export let isCloseable = true;
   export let isOpen = true;
   export let tabs: Tab[] = [];
-  export let activeTabID: string = '';
+  export let activeTabID = '';
   export let title: string;
   $: isOpen = isCloseable ? isOpen : true;
   $: isTabsShown = isOpen && tabs.length > 0;

src/lib/components/Card/__snapshots__/card.test.ts.snap

@@ -0,0 +1,3 @@
+// Vitest Snapshot v1
+
+exports[`card.svelte > mounts 1`] = `"<div><div class=\\"card rounded overflow-hidden m-2 flex-grow flex flex-col shadow-2xl\\"><div class=\\"bg-primary p-2 pb-0 flex-none cursor-pointer\\"><div class=\\"flex justify-between\\"><div class=\\"flex cursor-default s-lTROw8sJayZ1\\"><span class=\\"mr-2 font-semibold s-lTROw8sJayZ1\\"><i class=\\"fas fa-chevron-right icon s-lTROw8sJayZ1 isOpen\\"></i> TabTest</span> <ul class=\\"tabs s-lTROw8sJayZ1\\"><div class=\\"tab tab-lifted tab-active s-lTROw8sJayZ1\\"><i class=\\"mr-1 fab fa-git-alt s-lTROw8sJayZ1\\"></i> title1 </div><div class=\\"tab tab-lifted text-primary-content s-lTROw8sJayZ1\\"><i class=\\"mr-1 far fa-bookmark s-lTROw8sJayZ1\\"></i> title2 </div></ul></div><!--<Tabs>--> <div class=\\"flex gap-x-4 items-center -mt-2\\"></div></div></div> <div class=\\"card-body p-0 flex-grow overflow-auto text-base-content\\"></div></div><!--<Card>--></div>"`;

src/lib/components/Card/card.test.ts

@@ -1,6 +1,6 @@
 import { cleanup, render } from '@testing-library/svelte';
 import { describe, expect, it, afterEach } from 'vitest';
-import Card from './card.svelte';
+import Card from './Card.svelte';
 
 describe('card.svelte', () => {
   // TODO: @testing-library/svelte claims to add this automatically but it doesn't work without explicit afterEach
@@ -10,8 +10,8 @@ describe('card.svelte', () => {
     const { container } = render(Card, {
       title: 'TabTest',
       tabs: [
-        { id: 't1', title: 'title1' },
+        { id: 't1', title: 'title1', icon: 'fab fa-git-alt' },
-        { id: 't2', title: 'title2' }
+        { id: 't2', title: 'title2', icon: 'far fa-bookmark' }
       ]
     });
     expect(container).toBeTruthy();

src/lib/components/Editor.svelte

@@ -8,9 +8,9 @@
   import initEditor from 'monaco-mermaid';
   import { logEvent } from '$lib/util/stats';
 
-  let divEl: HTMLDivElement = null;
+  let divEl: HTMLDivElement | undefined = undefined;
-  let editor: monaco.editor.IStandaloneCodeEditor;
+  let editor: monaco.editor.IStandaloneCodeEditor | undefined;
-  let Monaco: typeof monaco;
+  let Monaco: typeof monaco | undefined;
   let editorOptions: monaco.editor.IStandaloneEditorConstructionOptions = {
     minimap: {
       enabled: false
@@ -22,7 +22,9 @@
 
   stateStore.subscribe(({ errorMarkers, editorMode, code, mermaid }) => {
     console.log('editor store subscription', { code, mermaid });
-    if (!editor) return;
+    if (!editor || !Monaco) {
+      return;
+    }
 
     // Update editor text if it's different
     const newText = editorMode === 'code' ? code : mermaid;
@@ -34,12 +36,17 @@
 
     // Update editor mode if it's different
     const language = editorMode === 'code' ? 'mermaid' : 'json';
-    if (editor.getModel().getLanguageId() !== language) {
+    const model = editor.getModel();
-      Monaco?.editor.setModelLanguage(editor.getModel(), language);
+    if (!model) {
+      console.error("editor model doesn't exist");
+      return;
+    }
+    if (model.getLanguageId() !== language) {
+      Monaco.editor.setModelLanguage(model, language);
     }
 
     // Display/clear errors
-    Monaco?.editor.setModelMarkers(editor.getModel(), 'mermaid', errorMarkers);
+    Monaco.editor.setModelMarkers(model, 'mermaid', errorMarkers);
   });
 
   themeStore.subscribe(({ isDark }) => {
@@ -60,7 +67,7 @@
     // errorDebug();
     let i = 0;
     while (i++ < 500) {
-      // @ts-ignore : This is a hack to handle a svelte-kit error when importing monaco.
+      // @ts-expect-error : This is a hack to handle a svelte-kit error when importing monaco.
       Monaco = window.monaco;
       if (Monaco !== undefined) {
         return;
@@ -72,13 +79,20 @@
 
   onMount(async () => {
     await loadMonaco(); // Fix https://github.com/mermaid-js/mermaid-live-editor/issues/175
+    if (!Monaco) {
+      throw new Error('Monaco failed to load');
+    }
+    if (!divEl) {
+      throw new Error('divEl is undefined');
+    }
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-call
     initEditor(Monaco);
     errorDebug(100);
     editor = Monaco.editor.create(divEl, editorOptions);
     editor.onDidChangeModelContent(({ isFlush, changes }) => {
-      const newText = editor.getValue();
+      const newText = editor?.getValue();
       console.log('editor onDidChangeModelContent', { text, newText, isFlush, changes });
-      if (text === newText || isFlush) {
+      if (!newText || text === newText || isFlush) {
         return;
       }
       text = newText;
@@ -95,19 +109,21 @@
         });
       }
     });
-    Monaco?.editor.setTheme($themeStore.isDark ? 'mermaid-dark' : 'mermaid');
+    Monaco.editor.setTheme($themeStore.isDark ? 'mermaid-dark' : 'mermaid');
     const resizeObserver = new ResizeObserver((entries) => {
-      editor.layout({
+      editor!.layout({
         height: entries[0].contentRect.height,
         width: entries[0].contentRect.width
       });
     });
 
-    resizeObserver.observe(divEl.parentElement);
+    if (divEl.parentElement) {
+      resizeObserver.observe(divEl.parentElement);
+    }
     console.log(`editor mounted`);
     return () => {
       console.log(`editor disposed`);
-      editor.dispose();
+      editor?.dispose();
     };
   });
 </script>

src/lib/components/History/History.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-  import Card from '$lib/components/card/card.svelte';
+  import Card from '$lib/components/Card/Card.svelte';
   import { inputStateStore, getStateString } from '$lib/util/state';
   import {
     addHistoryEntry,
@@ -14,7 +14,7 @@
   import { onMount } from 'svelte';
   import { get } from 'svelte/store';
   import moment from 'moment';
-  import type { HistoryType, State, Tab } from '$lib/types';
+  import type { HistoryEntry, HistoryType, State, Tab } from '$lib/types';
   import { logEvent } from '$lib/util/stats';
 
   const HISTORY_SAVE_INTERVAL = 60000;
@@ -60,7 +60,7 @@
       }
       const reader = new FileReader();
       reader.onload = (e) => {
-        const data = JSON.parse(e.target.result as string);
+        const data: HistoryEntry[] = JSON.parse(e.target.result as string);
         restoreHistory(data);
       };
       reader.readAsText(file);

src/lib/components/History/history.test.ts

@@ -7,7 +7,7 @@ import {
   historyModeStore,
   historyStore
 } from './history';
-import { defaultState } from '../../util/state';
+import { defaultState } from '$lib/util/state';
 import { get } from 'svelte/store';
 
 describe('history', () => {
@@ -21,9 +21,9 @@ describe('history', () => {
       type: 'manual'
     });
 
-    const [manualEntry]: HistoryEntry[] = JSON.parse(
+    const [manualEntry] = JSON.parse(
-      window.localStorage.getItem('manualHistoryStore')
+      window.localStorage.getItem('manualHistoryStore') ?? '[]'
-    );
+    ) as HistoryEntry[];
 
     expect(manualEntry.time).toBe(12345);
     expect(manualEntry.type).toBe('manual');
@@ -36,7 +36,9 @@ describe('history', () => {
       type: 'auto'
     });
 
-    const [autoEntry]: HistoryEntry[] = JSON.parse(window.localStorage.getItem('autoHistoryStore'));
+    const [autoEntry] = JSON.parse(
+      window.localStorage.getItem('autoHistoryStore') ?? '[]'
+    ) as HistoryEntry[];
 
     expect(autoEntry.time).toBe(54321);
     expect(autoEntry.type).toBe('auto');
@@ -101,19 +103,23 @@ describe('history migration', () => {
       'autoHistoryStore',
       '[{"state":{"code":"graph TD\\n    A[New Year] -->|Get money| B(Go shopping)","mermaid":"{\\n  \\"theme\\": \\"dark\\"\\n}","autoSync":true,"updateDiagram":false},"time":0,"type":"auto","name":"barking-dog"},{"state":{"code":"graph TD\\n    A[Christmas] -->|Get money| B(Go shopping)","mermaid":"{\\n  \\"theme\\": \\"dark\\"\\n}","autoSync":true,"updateDiagram":true},"time":0,"type":"manual","name":"needy-mosquito"}]'
     );
-    let manualHistoryStore: HistoryEntry[] = JSON.parse(
+    let manualHistoryStore = JSON.parse(
-      window.localStorage.getItem('manualHistoryStore')
+      window.localStorage.getItem('manualHistoryStore') ?? '[]'
-    );
+    ) as HistoryEntry[];
-    let autoHistoryStore: HistoryEntry[] = JSON.parse(
+    let autoHistoryStore = JSON.parse(
-      window.localStorage.getItem('autoHistoryStore')
+      window.localStorage.getItem('autoHistoryStore') ?? '[]'
-    );
+    ) as HistoryEntry[];
     expect(manualHistoryStore.every(({ id }) => id !== undefined)).toBe(false);
     expect(autoHistoryStore.every(({ id }) => id !== undefined)).toBe(false);
 
     injectHistoryIDs();
 
-    manualHistoryStore = JSON.parse(window.localStorage.getItem('manualHistoryStore'));
+    manualHistoryStore = JSON.parse(
-    autoHistoryStore = JSON.parse(window.localStorage.getItem('autoHistoryStore'));
+      window.localStorage.getItem('manualHistoryStore') ?? '[]'
+    ) as HistoryEntry[];
+    autoHistoryStore = JSON.parse(
+      window.localStorage.getItem('autoHistoryStore') ?? '[]'
+    ) as HistoryEntry[];
     expect(manualHistoryStore.every(({ id }) => id !== undefined)).toBe(true);
     expect(autoHistoryStore.every(({ id }) => id !== undefined)).toBe(true);
   });

src/lib/components/Navbar.svelte

@@ -1,13 +1,13 @@
-<script context="module">
+<script context="module" lang="ts">
   import { version } from 'mermaid/package.json';
   import { analytics } from '$lib/util/stats';
-  analytics?.track('version', {
+  void analytics?.track('version', {
     mermaidVersion: version
   });
 </script>
 
 <script lang="ts">
-  import Theme from './theme.svelte';
+  import Theme from './Theme.svelte';
 
   interface Link {
     title: string;

src/lib/components/Preset.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
   import { updateCode } from '$lib/util/state';
-  import Card from '$lib/components/card/card.svelte';
+  import Card from '$lib/components/Card/Card.svelte';
   import { logEvent } from '$lib/util/stats';
 
   const samples = {
@@ -104,7 +104,8 @@
       Mermaid`
   };
 
-  const loadSampleDiagram = (diagramType: string): void => {
+  type SampleTypes = keyof typeof samples;
+  const loadSampleDiagram = (diagramType: SampleTypes): void => {
     updateCode(samples[diagramType], {
       updateDiagram: true,
       resetPanZoom: true
@@ -113,8 +114,8 @@
   };
 
   // Adding in this array will add an icon to the preset menu
-  const newDiagrams: Array<keyof typeof samples> = ['Mindmap'];
+  const newDiagrams: SampleTypes[] = ['Mindmap'];
-  const diagramOrder: Array<keyof typeof samples> = [
+  const diagramOrder: SampleTypes[] = [
     'Sequence',
     'Flow',
     'Class',

src/lib/components/Theme.svelte

@@ -1,4 +1,4 @@
-<script>
+<script lang="ts">
   import { setTheme, themeStore } from '$lib/util/theme';
 
   const themes = [
@@ -52,7 +52,7 @@
     <!-- svelte-ignore a11y-no-noninteractive-tabindex -->
     <ul tabindex="0" class="p-4 menu compact">
       {#each themes as theme}
-        <li class={theme.includes($themeStore.theme) ? 'bordered' : ''}>
+        <li class:bordered={$themeStore.theme !== undefined && theme.includes($themeStore.theme)}>
           <span
             class="btn btn-ghost justify-start"
             on:click={() => setTheme(theme)}

src/lib/components/View.svelte

@@ -4,8 +4,9 @@
   import panzoom from 'svg-pan-zoom';
   import type { State, ValidatedState } from '$lib/types';
   import { logEvent } from '$lib/util/stats';
-  import { AsyncQueue, cmdKey } from '$lib/util/util';
+  import { cmdKey } from '$lib/util/util';
   import { render as renderDiagram } from '$lib/util/mermaid';
+  import type { MermaidConfig } from 'mermaid';
 
   let code = '';
   let config = '';
@@ -16,9 +17,12 @@
   let hide = false;
   let manualUpdate = true;
   let panZoomEnabled = $stateStore.panZoom;
-  let pzoom: SvgPanZoom.Instance;
+  let pzoom: typeof panzoom | undefined;
 
   const handlePanZoomChange = () => {
+    if (!pzoom) {
+      return;
+    }
     const pan = pzoom.getPan();
     const zoom = pzoom.getZoom();
     updateCodeStore({ pan, zoom });
@@ -32,8 +36,11 @@
     hide = true;
     pzoom?.destroy();
     pzoom = undefined;
-    Promise.resolve().then(() => {
+    void Promise.resolve().then(() => {
       const graphDiv = document.getElementById('graph-div');
+      if (!graphDiv) {
+        return;
+      }
       pzoom = panzoom(graphDiv, {
         onPan: handlePanZoomChange,
         onZoom: handlePanZoomChange,
@@ -70,10 +77,10 @@
         code = state.code;
         config = state.mermaid;
         panZoomEnabled = state.panZoom;
-        const scroll = view.parentElement.scrollTop;
+        const scroll = view.parentElement!.scrollTop;
         delete container.dataset.processed;
         await renderDiagram(
-          Object.assign({}, JSON.parse(state.mermaid)),
+          Object.assign({}, JSON.parse(state.mermaid)) as MermaidConfig,
           code,
           'graph-div',
           (svgCode, bindFunctions) => {
@@ -82,6 +89,9 @@
               container.innerHTML = svgCode;
               // console.log(container.innerHTML);
               const graphDiv = document.getElementById('graph-div');
+              if (!graphDiv) {
+                throw new Error('graph-div not found');
+              }
               graphDiv.setAttribute('height', '100%');
               graphDiv.style.maxWidth = '100%';
               if (bindFunctions) {
@@ -90,7 +100,7 @@
             }
           }
         );
-        view.parentElement.scrollTop = scroll;
+        view.parentElement!.scrollTop = scroll;
         error = false;
       } else if (manualUpdate) {
         manualUpdate = false;
@@ -103,11 +113,9 @@
     }
   };
 
-  const q = new AsyncQueue(handleStateChange);
-
   onMount(() => {
-    stateStore.subscribe(async (state) => {
+    stateStore.subscribe((state) => {
-      await q.process(state);
+      void handleStateChange(state);
     });
     window.addEventListener('resize', () => {
       if ($stateStore.panZoom && pzoom) {
@@ -120,12 +128,12 @@
 
 {#if (error && $stateStore.error instanceof Error) || outOfSync}
   <div
-    class="absolute w-full p-2 z-10 {error
+    class="absolute w-full p-2 z-10 font-mono {error
       ? 'text-red-600'
       : 'text-yellow-600'} bg-base-100 bg-opacity-80 text-center"
     id="errorContainer">
     {#if error}
-      {$stateStore.error}
+      {@html $stateStore.error.toString().replace(/\n/g, '<br />')}
     {:else}
       Diagram out of sync. <br />
       Press <i class="fas fa-sync" /> (Sync button) or <kbd>{cmdKey} + Enter</kbd> to sync.

src/lib/components/card/__snapshots__/card.test.ts.snap

@@ -1,3 +0,0 @@
-// Vitest Snapshot v1
-
-exports[`card.svelte > mounts 1`] = `"<div><div class=\\"card rounded overflow-hidden m-2 flex-grow flex flex-col shadow-2xl\\"><div class=\\"bg-primary p-2 pb-0 flex-none cursor-pointer\\"><div class=\\"flex justify-between\\"><div class=\\"flex cursor-default s-_wx1E_JHsCoF\\"><span class=\\"mr-2 font-semibold s-_wx1E_JHsCoF\\"><i class=\\"fas fa-chevron-right icon s-_wx1E_JHsCoF isOpen\\"></i> TabTest</span> <ul class=\\"tabs s-_wx1E_JHsCoF\\"><div class=\\"tab tab-lifted tab-active s-_wx1E_JHsCoF\\"><i class=\\"mr-1 undefined s-_wx1E_JHsCoF\\"></i> title1 </div><div class=\\"tab tab-lifted text-primary-content s-_wx1E_JHsCoF\\"><i class=\\"mr-1 undefined s-_wx1E_JHsCoF\\"></i> title2 </div></ul></div><!--<Tabs>--> <div class=\\"flex gap-x-4 items-center -mt-2\\"></div></div></div> <div class=\\"card-body p-0 flex-grow overflow-auto text-base-content\\"></div></div><!--<Card>--></div>"`;

src/lib/types.d.ts

@@ -1,11 +1,3 @@
-/**
- * Can be made globally available by placing this
- * inside `global.d.ts` and removing `export` keyword
- */
-export interface Locals {
-  userid: string;
-}
-
 export interface MarkerData {
   severity: number;
   message: string;
@@ -40,7 +32,7 @@ export interface State {
 
 export interface ValidatedState extends State {
   editorMode: EditorMode;
-  error: unknown;
+  error?: Error;
   errorMarkers: MarkerData[];
   serialized: string;
 }
@@ -73,14 +65,24 @@ export type HistoryEntry = { id: string; state: State; time: number; url?: strin
     }
 );
 
-export interface DocConfig {
+export type DocConfig = Record<
-  [key: string]: {
+  string,
+  {
     code: string;
     config?: string;
-  };
+  }
-}
+>;
 
 export type EditorMode = 'code' | 'config';
 
 export type Loader = (url: string) => Promise<State>;
 export type Optional<T, K extends keyof T> = Pick<Partial<T>, K> & Omit<T, K>;
+
+export interface ErrorHash {
+  loc: {
+    first_line: number;
+    last_line: number;
+    first_column: number;
+    last_column: number;
+  };
+}

src/lib/util/fileLoaders/gist.ts

@@ -3,17 +3,23 @@
 /* eslint-disable @typescript-eslint/no-unsafe-member-access */
 /* eslint-disable @typescript-eslint/no-explicit-any */
 import type { State } from '$lib/types';
-import { defaultState } from '../state';
+import { defaultState } from '$lib/util/state';
-import { addHistoryEntry } from '../../components/history/history';
+import { addHistoryEntry } from '$lib/components/History/history';
 
 const codeFileName = 'code.mmd';
 const configFileName = 'config.json';
 
+interface GithubFile {
+  truncated: boolean;
+  raw_url: string;
+  content: string;
+}
+
 const isValidGist = (files: any): boolean => {
   return codeFileName in files;
 };
 
-const getFileContent = async (file: any): Promise<string> => {
+const getFileContent = async (file: GithubFile): Promise<string> => {
   if (file.truncated) {
     return await (await fetch(file.raw_url)).text();
   }
@@ -29,16 +35,26 @@ interface GistData {
   url: string;
 }
 
+interface GistResponse {
+  files: Record<string, GithubFile>;
+  html_url: string;
+  history: { url: string; committed_at: string; version: string; user: { login: string } }[];
+}
+
 const getGistData = async (gistURL: string): Promise<GistData> => {
+  const path = gistURL.split('github.com').pop();
+  if (!path) {
+    throw new Error('Invalid GitHub URL' + gistURL);
+  }
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
-  const [_, __, gistID, revisionID] = gistURL.split('github.com').pop().split('/');
+  const [_, __, gistID, revisionID] = path.split('/');
   // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
-  const { html_url, files, history } = await (
+  const { html_url, files, history }: GistResponse = await (
     await fetch(`https://api.github.com/gists/${gistID}${revisionID ? '/' + revisionID : ''}`)
   ).json();
   if (isValidGist(files)) {
     const code = await getFileContent(files[codeFileName]);
-    let config: string;
+    let config = '{}';
     if (configFileName in files) {
       config = await getFileContent(files[configFileName]);
     }
@@ -50,10 +66,10 @@ const getGistData = async (gistURL: string): Promise<GistData> => {
       config,
       author: currentItem.user.login,
       time: new Date(currentItem.committed_at).getTime(),
-      version: (currentItem.version as string).slice(-7)
+      version: currentItem.version.slice(-7)
     };
   } else {
-    throw 'Invalid gist provided';
+    throw new Error('Invalid gist provided');
   }
 };
 
@@ -73,35 +89,38 @@ const getStateFromGist = (gist: GistData, gistURL: string = gist.url): State =>
 };
 
 export const loadGistData = async (gistURL: string): Promise<State> => {
-  try {
+  const path = gistURL.split('github.com').pop();
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  if (!path) {
-    const [_, __, gistID, revisionID] = gistURL.split('github.com').pop().split('/');
+    throw new Error('Invalid GitHub URL' + gistURL);
-    // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
-    const { history } = await (
-      await fetch(`https://api.github.com/gists/${gistID}${revisionID ? '/' + revisionID : ''}`)
-    ).json();
-    const gistHistory: GistData[] = [];
-    for (const entry of history) {
-      // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
-      const data: GistData = await getGistData(entry.url).catch(() => undefined);
-      data && gistHistory.push(data);
-    }
-    if (gistHistory.length === 0) {
-      throw 'Invalid gist provided';
-    }
-    gistHistory.reverse();
-    const state = getStateFromGist(gistHistory.slice(-1).pop(), gistURL);
-    for (const gist of gistHistory) {
-      addHistoryEntry({
-        state: getStateFromGist(gist),
-        time: gist.time,
-        type: 'loader',
-        url: gist.url,
-        name: `${gist.author} v${gist.version}`
-      });
-    }
-    return state;
-  } catch (err) {
-    console.error(err);
   }
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  const [_, __, gistID, revisionID] = path.split('/');
+  // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+  const { history }: GistResponse = await (
+    await fetch(`https://api.github.com/gists/${gistID}${revisionID ? '/' + revisionID : ''}`)
+  ).json();
+  const gistHistory: GistData[] = [];
+  for (const entry of history) {
+    const data: GistData | undefined = await getGistData(entry.url).catch(() => undefined);
+    data && gistHistory.push(data);
+  }
+  if (gistHistory.length === 0) {
+    throw new Error('Invalid gist provided');
+  }
+  gistHistory.reverse();
+  const entry = gistHistory.slice(-1).pop();
+  if (!entry) {
+    throw new Error('Invalid gist provided');
+  }
+  const state = getStateFromGist(entry, gistURL);
+  for (const gist of gistHistory) {
+    addHistoryEntry({
+      state: getStateFromGist(gist),
+      time: gist.time,
+      type: 'loader',
+      url: gist.url,
+      name: `${gist.author} v${gist.version}`
+    });
+  }
+  return state;
 };

src/lib/util/fileLoaders/loader.ts

@@ -8,10 +8,11 @@ const loaders: Record<string, Loader> = {
 export const loadDataFromUrl = async (): Promise<void> => {
   const searchParams = new URLSearchParams(window.location.search);
   let state: Partial<State> = defaultState;
-  let code: string, config: string;
+  let code: string | undefined = undefined;
+  let config: string | undefined = undefined;
   let loaded = false;
-  const codeURL: string = searchParams.get('code');
+  const codeURL: string | undefined = searchParams.get('code') ?? undefined;
-  const configURL: string = searchParams.get('config');
+  const configURL: string | undefined = searchParams.get('config') ?? undefined;
 
   if (codeURL) {
     code = await (await fetch(codeURL)).text();
@@ -23,9 +24,6 @@ export const loadDataFromUrl = async (): Promise<void> => {
     config = defaultState.mermaid;
   }
   if (!code) {
-    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
-    // @ts-ignore
-    // eslint-disable-next-line @typescript-eslint/no-unsafe-call
     for (const [key, value] of searchParams.entries()) {
       if (key in loaders) {
         try {
@@ -38,6 +36,9 @@ export const loadDataFromUrl = async (): Promise<void> => {
       }
     }
   } else {
+    if (!codeURL) {
+      throw new Error('Code URL is not defined');
+    }
     state = {
       code,
       mermaid: config,

src/lib/util/mermaid.ts

@@ -23,5 +23,5 @@ export const render = async (
 
 export const parse = async (code: string): Promise<boolean> => {
   await init();
-  return (await mermaid.parseAsync(code)) as boolean;
+  return await mermaid.parseAsync(code);
 };

src/lib/util/migrations.test.ts

@@ -16,18 +16,22 @@ describe('migrations', () => {
   it('should migrate from v0 to v1', async () => {
     const { applyMigrations } = await import('./migrations');
     let manualHistoryStore: HistoryEntry[] = JSON.parse(
-      window.localStorage.getItem('manualHistoryStore')
+      window.localStorage.getItem('manualHistoryStore') ?? '[]'
-    );
+    ) as HistoryEntry[];
     let autoHistoryStore: HistoryEntry[] = JSON.parse(
-      window.localStorage.getItem('autoHistoryStore')
+      window.localStorage.getItem('autoHistoryStore') ?? '[]'
-    );
+    ) as HistoryEntry[];
     expect(manualHistoryStore.every(({ id }) => id !== undefined)).toBe(false);
     expect(autoHistoryStore.every(({ id }) => id !== undefined)).toBe(false);
 
     applyMigrations();
 
-    manualHistoryStore = JSON.parse(window.localStorage.getItem('manualHistoryStore'));
+    manualHistoryStore = JSON.parse(
-    autoHistoryStore = JSON.parse(window.localStorage.getItem('autoHistoryStore'));
+      window.localStorage.getItem('manualHistoryStore') ?? '[]'
+    ) as HistoryEntry[];
+    autoHistoryStore = JSON.parse(
+      window.localStorage.getItem('autoHistoryStore') ?? '[]'
+    ) as HistoryEntry[];
     expect(manualHistoryStore.every(({ id }) => id !== undefined)).toBe(true);
     expect(autoHistoryStore.every(({ id }) => id !== undefined)).toBe(true);
   });

src/lib/util/migrations.ts

@@ -1,13 +1,13 @@
 import { writable, get, type Writable } from 'svelte/store';
 import { persist, localStorage } from '$lib/util/persist';
-import { injectHistoryIDs } from '$lib/components/history/history';
+import { injectHistoryIDs } from '$lib/components/History/history';
 import { logEvent } from './stats';
 
 interface MigrationState {
   version: number;
 }
 
-const migrations: { [key: string]: () => void } = {
+const migrations: Record<string, () => void> = {
   injectHistoryIDs
 };
 

src/lib/util/persist.ts

@@ -39,16 +39,16 @@ let noWarnings = false;
 /**
  * List of storages where the warning have already been displayed.
  */
-const alreadyWarnFor: Array<string> = [];
+const alreadyWarnFor: string[] = [];
 
 /**
  * Add a log to indicate that the requested Storage have not been found.
  * @param {string} storageName
  */
-const warnStorageNotFound = (storageName) => {
+const warnStorageNotFound = (storageName: string) => {
-  const isProduction = typeof process !== 'undefined' && process.env?.NODE_ENV === 'production';
+  const isProduction = typeof process !== 'undefined' && process.env.NODE_ENV === 'production';
 
-  if (!noWarnings && alreadyWarnFor.indexOf(storageName) === -1 && !isProduction) {
+  if (!noWarnings && !alreadyWarnFor.includes(storageName) && !isProduction) {
     let message = `Unable to find the ${storageName}. No data will be persisted.`;
     if (typeof window === 'undefined') {
       message +=
@@ -60,17 +60,8 @@ const warnStorageNotFound = (storageName) => {
   }
 };
 
-const allowedClasses = [];
-/**
- * Add a class to the allowed list of classes to be serialized
- * @param classDef The class to add to the list
- */
-export const addSerializableClass = (classDef: () => unknown): void => {
-  allowedClasses.push(classDef);
-};
-
 const serialize = (value: unknown): string => ESSerializer.serialize(value);
-const deserialize = (value: string): unknown => {
+const deserialize = (value?: string | null): unknown => {
   // @TODO: to remove in the next major
   if (value === 'undefined') {
     return undefined;
@@ -78,7 +69,7 @@ const deserialize = (value: string): unknown => {
 
   if (value !== null && value !== undefined) {
     try {
-      return ESSerializer.deserialize(value, allowedClasses);
+      return ESSerializer.deserialize(value);
     } catch (e) {
       // Do nothing
       // use the value "as is"
@@ -162,7 +153,7 @@ export function persist<T>(
     store.set(initialValue);
   }
 
-  if ((storage as SelfUpdateStorageInterface<T>).addListener) {
+  if ('addListener' in storage) {
     (storage as SelfUpdateStorageInterface<T>).addListener(key, (newValue) => {
       store.set(newValue);
     });
@@ -184,7 +175,7 @@ function getBrowserStorage(
   browserStorage: Storage,
   listenExternalChanges = false
 ): SelfUpdateStorageInterface<any> {
-  const listeners: Array<{ key: string; listener: (newValue: any) => void }> = [];
+  const listeners: { key: string; listener: (newValue: any) => void }[] = [];
   const listenerFunction = (event: StorageEvent) => {
     const eventKey = event.key;
     if (event.storageArea === browserStorage) {
@@ -196,12 +187,14 @@ function getBrowserStorage(
     }
   };
   const connect = () => {
-    if (listenExternalChanges && typeof window !== 'undefined' && window?.addEventListener) {
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+    if (listenExternalChanges && typeof window !== 'undefined' && window.addEventListener) {
       window.addEventListener('storage', listenerFunction);
     }
   };
   const disconnect = () => {
-    if (listenExternalChanges && typeof window !== 'undefined' && window?.removeEventListener) {
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+    if (listenExternalChanges && typeof window !== 'undefined' && window.removeEventListener) {
       window.removeEventListener('storage', listenerFunction);
     }
   };
@@ -237,10 +230,11 @@ function getBrowserStorage(
 
 /**
  * Storage implementation that use the browser local storage
- * @param {boolean} listenExternalChanges - Update the store if the localStorage is updated from another page
+ * @param listenExternalChanges - Update the store if the localStorage is updated from another page
  */
 export function localStorage<T>(listenExternalChanges = false): StorageInterface<T> {
-  if (typeof window !== 'undefined' && window?.localStorage) {
+  // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+  if (typeof window !== 'undefined' && window.localStorage) {
     return getBrowserStorage(window.localStorage, listenExternalChanges);
   }
   warnStorageNotFound('window.localStorage');
@@ -250,7 +244,7 @@ export function localStorage<T>(listenExternalChanges = false): StorageInterface
 /**
  * Storage implementation that do nothing
  */
-export function noopStorage(): StorageInterface<any> {
+export function noopStorage<T>(): StorageInterface<T> {
   return {
     getValue(): null {
       return null;

src/lib/util/serde.ts

@@ -36,7 +36,7 @@ const serdes: { [key in SerdeType]: Serde } = {
 };
 
 export const serializeState = (state: State, serde: SerdeType = 'pako'): string => {
-  if (serdes[serde] === undefined) {
+  if (!(serde in serdes)) {
     throw new Error(`Unknown serde type: ${serde}`);
   }
   const json = JSON.stringify(state);

src/lib/util/state.ts

@@ -2,10 +2,12 @@ import { writable, get, type Readable, derived } from 'svelte/store';
 import { persist, localStorage } from './persist';
 import { saveStatistics, countLines } from './stats';
 import { serializeState, deserializeState } from './serde';
-import { cmdKey, errorDebug, AsyncQueue } from './util';
+import { cmdKey, errorDebug } from './util';
 import { parse } from './mermaid';
 
-import type { MarkerData, State, ValidatedState } from '$lib/types';
+import type { ErrorHash, MarkerData, State, ValidatedState } from '$lib/types';
+import type { MermaidConfig } from 'mermaid';
+
 export const defaultState: State = {
   code: `graph TD
     A[Christmas] -->|Get money| B(Go shopping)
@@ -50,8 +52,6 @@ export const currentState: ValidatedState = (() => {
   };
 })();
 
-let q: AsyncQueue<State>;
-
 const processState = async (state: State) => {
   const processed: ValidatedState = {
     ...state,
@@ -66,17 +66,22 @@ const processState = async (state: State) => {
     await parse(state.code);
     JSON.parse(state.mermaid);
   } catch (e) {
-    processed.error = e;
+    processed.error = e as Error;
     errorDebug();
     console.error(e);
-    if (e.hash) {
+    if ('hash' in e) {
       try {
+        const {
+          loc: { first_line, last_line, first_column, last_column }
+          // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
+        } = e.hash as ErrorHash;
         const marker: MarkerData = {
           severity: 8, // Error
-          startLineNumber: e.hash.loc.first_line,
+          startLineNumber: first_line,
-          startColumn: e.hash.loc.first_column,
+          startColumn: first_column,
-          endLineNumber: e.hash.loc.last_line,
+          endLineNumber: last_line,
-          endColumn: (e.hash.loc.last_column as number) + 1,
+          endColumn: last_column + 1,
+          // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-assignment
           message: e.str
         };
         processed.errorMarkers = [marker];
@@ -92,14 +97,7 @@ const processState = async (state: State) => {
 export const stateStore: Readable<ValidatedState> = derived(
   [inputStateStore],
   ([state], set) => {
-    if (!q) {
+    void processState(state).then(set);
-      // Initialize the queue for first time.
-      q = new AsyncQueue(async (state: State) => {
-        const newState = await processState(state);
-        set(newState);
-      });
-    }
-    q.process(state);
   },
   currentState
 );
@@ -109,8 +107,10 @@ export const loadState = (data: string): void => {
   console.log(`Loading '${data}'`);
   try {
     state = deserializeState(data);
-    const mermaidConfig: { [key: string]: string } =
+    const mermaidConfig: MermaidConfig =
-      typeof state.mermaid === 'string' ? JSON.parse(state.mermaid) : state.mermaid;
+      typeof state.mermaid === 'string'
+        ? (JSON.parse(state.mermaid) as MermaidConfig)
+        : state.mermaid;
     if (
       mermaidConfig.securityLevel &&
       mermaidConfig.securityLevel !== 'strict' &&
@@ -180,7 +180,7 @@ export const updateConfig = (config: string): void => {
 
 export const toggleDarkTheme = (dark: boolean): void => {
   inputStateStore.update((state) => {
-    const config = JSON.parse(state.mermaid);
+    const config = JSON.parse(state.mermaid) as MermaidConfig;
     if (!config.theme || ['dark', 'default'].includes(config.theme)) {
       config.theme = dark ? 'dark' : 'default';
     }
@@ -194,7 +194,7 @@ export const initURLSubscription = (): void => {
   stateStore.subscribe(({ serialized }) => {
     clearTimeout(urlDebounce);
     urlDebounce = window.setTimeout(() => {
-      history.replaceState(undefined, undefined, `#${serialized}`);
+      history.replaceState(undefined, '', `#${serialized}`);
     }, 250);
   });
 };

src/lib/util/stats.ts

@@ -1,6 +1,6 @@
 import { browser } from '$app/environment';
 import type { AnalyticsInstance } from 'analytics';
-export let analytics: AnalyticsInstance;
+export let analytics: AnalyticsInstance | undefined;
 
 export const initAnalytics = async (): Promise<void> => {
   if (browser && !analytics) {
@@ -27,7 +27,7 @@ export const initAnalytics = async (): Promise<void> => {
   }
 };
 
-export const detectType = (text: string): string => {
+export const detectType = (text: string): string | undefined => {
   const possibleDiagramTypes = [
     'classDiagram',
     'erDiagram',
@@ -49,7 +49,7 @@ export const detectType = (text: string): string => {
 };
 
 export const countLines = (code: string): number => {
-  return (code.match(/\n/g) || '').length + 1;
+  return (code.match(/\n/g)?.length ?? 0) + 1;
 };
 
 export const saveStatistics = (graph: string): void => {
@@ -80,19 +80,20 @@ const delaysPerEvent = {
   themeChange: defaultDelay
 };
 export type AnalyticsEvent = keyof typeof delaysPerEvent;
-const timeouts: Record<string, number> = {};
+const timeouts: Map<string, number> = new Map<string, number>();
 // manual debounce to reduce the number of events sent to analytics
 export const logEvent = (name: AnalyticsEvent, data?: unknown): void => {
   if (!analytics) {
     return;
   }
   const key = data ? JSON.stringify({ name, data }) : name;
-  if (timeouts[key] === undefined) {
+  if (!timeouts.has(key)) {
     void analytics.track(name, data);
   } else {
-    clearTimeout(timeouts[key]);
+    clearTimeout(timeouts.get(key));
   }
-  timeouts[key] = window.setTimeout(() => {
+  timeouts.set(
-    delete timeouts[key];
+    key,
-  }, delaysPerEvent[name]);
+    window.setTimeout(() => timeouts.delete(key), delaysPerEvent[name])
+  );
 };

src/lib/util/util.ts

@@ -23,10 +23,10 @@ export const initHandler = async (): Promise<void> => {
   syncDiagram();
   initURLSubscription();
   await initAnalytics();
-  analytics?.page();
+  await analytics?.page();
 };
 
-export const isMac = navigator.platform.toUpperCase().indexOf('MAC') >= 0;
+export const isMac = navigator.platform.toUpperCase().includes('MAC');
 export const cmdKey = isMac ? 'Cmd' : 'Ctrl';
 
 let count = 0;
@@ -38,24 +38,3 @@ export const errorDebug = (limit = 100) => {
     debugger;
   }
 };
-
-// To queue async tasks so they are executed one after the other, not concurrently.
-export class AsyncQueue<T> {
-  private readonly queue: T[] = [];
-  private running = false;
-  constructor(private processor: (item: T) => Promise<void>) {}
-  public async process(item: T): Promise<void> {
-    this.queue.push(item);
-    if (this.running) {
-      return;
-    }
-    this.running = true;
-    while (this.queue.length > 0) {
-      const item = this.queue.shift();
-      if (item) {
-        await this.processor(item);
-      }
-    }
-    this.running = false;
-  }
-}

src/routes/+layout.js

@@ -1,3 +1,4 @@
 export const prerender = true;
 export const csr = true;
 export const ssr = false;
+export const trailingSlash = 'ignore';

src/routes/+layout.svelte

@@ -10,8 +10,8 @@
   // This can be removed once https://github.com/sveltejs/kit/issues/1612 is fixed.
   // Then move it into src and vite will bundle it automatically.
   onMount(() => {
-    window.addEventListener('hashchange', async (ev) => {
+    window.addEventListener('hashchange', () => {
-      await initHandler();
+      void initHandler();
     });
     if ('serviceWorker' in navigator) {
       navigator.serviceWorker

src/routes/edit/+page.svelte

@@ -1,11 +1,11 @@
 <script lang="ts">
-  import Editor from '$lib/components/editor.svelte';
+  import Editor from '$lib/components/Editor.svelte';
-  import Navbar from '$lib/components/navbar.svelte';
+  import Navbar from '$lib/components/Navbar.svelte';
-  import Preset from '$lib/components/preset.svelte';
+  import Preset from '$lib/components/Preset.svelte';
-  import Actions from '$lib/components/actions.svelte';
+  import Actions from '$lib/components/Actions.svelte';
-  import View from '$lib/components/view.svelte';
+  import View from '$lib/components/View.svelte';
-  import Card from '$lib/components/card/card.svelte';
+  import Card from '$lib/components/Card/Card.svelte';
-  import History from '$lib/components/history/history.svelte';
+  import History from '$lib/components/History/History.svelte';
   import { inputStateStore, stateStore, updateCodeStore } from '$lib/util/state';
   import { cmdKey, initHandler, syncDiagram } from '$lib/util/util';
   import { onMount } from 'svelte';
@@ -86,6 +86,10 @@
     await initHandler();
     const resizer = document.getElementById('resizeHandler');
     const element = document.getElementById('editorPane');
+    if (!resizer || !element) {
+      console.debug('Failed to find resize handler or editor pane', { resizer, element });
+      return;
+    }
     const resize = (e: { pageX: number }) => {
       const newWidth = e.pageX - element.getBoundingClientRect().left;
       if (newWidth > 50) {

src/routes/view/+page.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-  import View from '$lib/components/view.svelte';
+  import View from '$lib/components/View.svelte';
   import { initHandler } from '$lib/util/util';
   import { onMount } from 'svelte';
   onMount(initHandler);

svelte.config.js

@@ -18,8 +18,7 @@ const config = {
       ? {
           base: `/mermaid-live-editor`
         }
-      : {},
+      : {}
-    trailingSlash: 'ignore'
   }
 };
 

tests-examples/demo-todo-app.spec.ts

@@ -0,0 +1,398 @@
+import { test, expect, type Page } from '@playwright/test';
+
+test.beforeEach(async ({ page }) => {
+  await page.goto('https://demo.playwright.dev/todomvc');
+});
+
+const TODO_ITEMS = [
+  'buy some cheese',
+  'feed the cat',
+  'book a doctors appointment'
+];
+
+test.describe('New Todo', () => {
+  test('should allow me to add todo items', async ({ page }) => {
+    // Create 1st todo.
+    await page.locator('.new-todo').fill(TODO_ITEMS[0]);
+    await page.locator('.new-todo').press('Enter');
+
+    // Make sure the list only has one todo item.
+    await expect(page.locator('.view label')).toHaveText([
+      TODO_ITEMS[0]
+    ]);
+
+    // Create 2nd todo.
+    await page.locator('.new-todo').fill(TODO_ITEMS[1]);
+    await page.locator('.new-todo').press('Enter');
+
+    // Make sure the list now has two todo items.
+    await expect(page.locator('.view label')).toHaveText([
+      TODO_ITEMS[0],
+      TODO_ITEMS[1]
+    ]);
+
+    await checkNumberOfTodosInLocalStorage(page, 2);
+  });
+
+  test('should clear text input field when an item is added', async ({ page }) => {
+    // Create one todo item.
+    await page.locator('.new-todo').fill(TODO_ITEMS[0]);
+    await page.locator('.new-todo').press('Enter');
+
+    // Check that input is empty.
+    await expect(page.locator('.new-todo')).toBeEmpty();
+    await checkNumberOfTodosInLocalStorage(page, 1);
+  });
+
+  test('should append new items to the bottom of the list', async ({ page }) => {
+    // Create 3 items.
+    await createDefaultTodos(page);
+
+    // Check test using different methods.
+    await expect(page.locator('.todo-count')).toHaveText('3 items left');
+    await expect(page.locator('.todo-count')).toContainText('3');
+    await expect(page.locator('.todo-count')).toHaveText(/3/);
+
+    // Check all items in one call.
+    await expect(page.locator('.view label')).toHaveText(TODO_ITEMS);
+    await checkNumberOfTodosInLocalStorage(page, 3);
+  });
+
+  test('should show #main and #footer when items added', async ({ page }) => {
+    await page.locator('.new-todo').fill(TODO_ITEMS[0]);
+    await page.locator('.new-todo').press('Enter');
+
+    await expect(page.locator('.main')).toBeVisible();
+    await expect(page.locator('.footer')).toBeVisible();
+    await checkNumberOfTodosInLocalStorage(page, 1);
+  });
+});
+
+test.describe('Mark all as completed', () => {
+  test.beforeEach(async ({ page }) => {
+    await createDefaultTodos(page);
+    await checkNumberOfTodosInLocalStorage(page, 3);
+  });
+
+  test.afterEach(async ({ page }) => {
+    await checkNumberOfTodosInLocalStorage(page, 3);
+  });
+
+  test('should allow me to mark all items as completed', async ({ page }) => {
+    // Complete all todos.
+    await page.locator('.toggle-all').check();
+
+    // Ensure all todos have 'completed' class.
+    await expect(page.locator('.todo-list li')).toHaveClass(['completed', 'completed', 'completed']);
+    await checkNumberOfCompletedTodosInLocalStorage(page, 3);
+  });
+
+  test('should allow me to clear the complete state of all items', async ({ page }) => {
+    // Check and then immediately uncheck.
+    await page.locator('.toggle-all').check();
+    await page.locator('.toggle-all').uncheck();
+
+    // Should be no completed classes.
+    await expect(page.locator('.todo-list li')).toHaveClass(['', '', '']);
+  });
+
+  test('complete all checkbox should update state when items are completed / cleared', async ({ page }) => {
+    const toggleAll = page.locator('.toggle-all');
+    await toggleAll.check();
+    await expect(toggleAll).toBeChecked();
+    await checkNumberOfCompletedTodosInLocalStorage(page, 3);
+
+    // Uncheck first todo.
+    const firstTodo = page.locator('.todo-list li').nth(0);
+    await firstTodo.locator('.toggle').uncheck();
+
+    // Reuse toggleAll locator and make sure its not checked.
+    await expect(toggleAll).not.toBeChecked();
+
+    await firstTodo.locator('.toggle').check();
+    await checkNumberOfCompletedTodosInLocalStorage(page, 3);
+
+    // Assert the toggle all is checked again.
+    await expect(toggleAll).toBeChecked();
+  });
+});
+
+test.describe('Item', () => {
+
+  test('should allow me to mark items as complete', async ({ page }) => {
+    // Create two items.
+    for (const item of TODO_ITEMS.slice(0, 2)) {
+      await page.locator('.new-todo').fill(item);
+      await page.locator('.new-todo').press('Enter');
+    }
+
+    // Check first item.
+    const firstTodo = page.locator('.todo-list li').nth(0);
+    await firstTodo.locator('.toggle').check();
+    await expect(firstTodo).toHaveClass('completed');
+
+    // Check second item.
+    const secondTodo = page.locator('.todo-list li').nth(1);
+    await expect(secondTodo).not.toHaveClass('completed');
+    await secondTodo.locator('.toggle').check();
+
+    // Assert completed class.
+    await expect(firstTodo).toHaveClass('completed');
+    await expect(secondTodo).toHaveClass('completed');
+  });
+
+  test('should allow me to un-mark items as complete', async ({ page }) => {
+    // Create two items.
+    for (const item of TODO_ITEMS.slice(0, 2)) {
+      await page.locator('.new-todo').fill(item);
+      await page.locator('.new-todo').press('Enter');
+    }
+
+    const firstTodo = page.locator('.todo-list li').nth(0);
+    const secondTodo = page.locator('.todo-list li').nth(1);
+    await firstTodo.locator('.toggle').check();
+    await expect(firstTodo).toHaveClass('completed');
+    await expect(secondTodo).not.toHaveClass('completed');
+    await checkNumberOfCompletedTodosInLocalStorage(page, 1);
+
+    await firstTodo.locator('.toggle').uncheck();
+    await expect(firstTodo).not.toHaveClass('completed');
+    await expect(secondTodo).not.toHaveClass('completed');
+    await checkNumberOfCompletedTodosInLocalStorage(page, 0);
+  });
+
+  test('should allow me to edit an item', async ({ page }) => {
+    await createDefaultTodos(page);
+
+    const todoItems = page.locator('.todo-list li');
+    const secondTodo = todoItems.nth(1);
+    await secondTodo.dblclick();
+    await expect(secondTodo.locator('.edit')).toHaveValue(TODO_ITEMS[1]);
+    await secondTodo.locator('.edit').fill('buy some sausages');
+    await secondTodo.locator('.edit').press('Enter');
+
+    // Explicitly assert the new text value.
+    await expect(todoItems).toHaveText([
+      TODO_ITEMS[0],
+      'buy some sausages',
+      TODO_ITEMS[2]
+    ]);
+    await checkTodosInLocalStorage(page, 'buy some sausages');
+  });
+});
+
+test.describe('Editing', () => {
+  test.beforeEach(async ({ page }) => {
+    await createDefaultTodos(page);
+    await checkNumberOfTodosInLocalStorage(page, 3);
+  });
+
+  test('should hide other controls when editing', async ({ page }) => {
+    const todoItem = page.locator('.todo-list li').nth(1);
+    await todoItem.dblclick();
+    await expect(todoItem.locator('.toggle')).not.toBeVisible();
+    await expect(todoItem.locator('label')).not.toBeVisible();
+    await checkNumberOfTodosInLocalStorage(page, 3);
+  });
+
+  test('should save edits on blur', async ({ page }) => {
+    const todoItems = page.locator('.todo-list li');
+    await todoItems.nth(1).dblclick();
+    await todoItems.nth(1).locator('.edit').fill('buy some sausages');
+    await todoItems.nth(1).locator('.edit').dispatchEvent('blur');
+
+    await expect(todoItems).toHaveText([
+      TODO_ITEMS[0],
+      'buy some sausages',
+      TODO_ITEMS[2],
+    ]);
+    await checkTodosInLocalStorage(page, 'buy some sausages');
+  });
+
+  test('should trim entered text', async ({ page }) => {
+    const todoItems = page.locator('.todo-list li');
+    await todoItems.nth(1).dblclick();
+    await todoItems.nth(1).locator('.edit').fill('    buy some sausages    ');
+    await todoItems.nth(1).locator('.edit').press('Enter');
+
+    await expect(todoItems).toHaveText([
+      TODO_ITEMS[0],
+      'buy some sausages',
+      TODO_ITEMS[2],
+    ]);
+    await checkTodosInLocalStorage(page, 'buy some sausages');
+  });
+
+  test('should remove the item if an empty text string was entered', async ({ page }) => {
+    const todoItems = page.locator('.todo-list li');
+    await todoItems.nth(1).dblclick();
+    await todoItems.nth(1).locator('.edit').fill('');
+    await todoItems.nth(1).locator('.edit').press('Enter');
+
+    await expect(todoItems).toHaveText([
+      TODO_ITEMS[0],
+      TODO_ITEMS[2],
+    ]);
+  });
+
+  test('should cancel edits on escape', async ({ page }) => {
+    const todoItems = page.locator('.todo-list li');
+    await todoItems.nth(1).dblclick();
+    await todoItems.nth(1).locator('.edit').press('Escape');
+    await expect(todoItems).toHaveText(TODO_ITEMS);
+  });
+});
+
+test.describe('Counter', () => {
+  test('should display the current number of todo items', async ({ page }) => {
+    await page.locator('.new-todo').fill(TODO_ITEMS[0]);
+    await page.locator('.new-todo').press('Enter');
+    await expect(page.locator('.todo-count')).toContainText('1');
+
+    await page.locator('.new-todo').fill(TODO_ITEMS[1]);
+    await page.locator('.new-todo').press('Enter');
+    await expect(page.locator('.todo-count')).toContainText('2');
+
+    await checkNumberOfTodosInLocalStorage(page, 2);
+  });
+});
+
+test.describe('Clear completed button', () => {
+  test.beforeEach(async ({ page }) => {
+    await createDefaultTodos(page);
+  });
+
+  test('should display the correct text', async ({ page }) => {
+    await page.locator('.todo-list li .toggle').first().check();
+    await expect(page.locator('.clear-completed')).toHaveText('Clear completed');
+  });
+
+  test('should remove completed items when clicked', async ({ page }) => {
+    const todoItems = page.locator('.todo-list li');
+    await todoItems.nth(1).locator('.toggle').check();
+    await page.locator('.clear-completed').click();
+    await expect(todoItems).toHaveCount(2);
+    await expect(todoItems).toHaveText([TODO_ITEMS[0], TODO_ITEMS[2]]);
+  });
+
+  test('should be hidden when there are no items that are completed', async ({ page }) => {
+    await page.locator('.todo-list li .toggle').first().check();
+    await page.locator('.clear-completed').click();
+    await expect(page.locator('.clear-completed')).toBeHidden();
+  });
+});
+
+test.describe('Persistence', () => {
+  test('should persist its data', async ({ page }) => {
+    for (const item of TODO_ITEMS.slice(0, 2)) {
+      await page.locator('.new-todo').fill(item);
+      await page.locator('.new-todo').press('Enter');
+    }
+
+    const todoItems = page.locator('.todo-list li');
+    await todoItems.nth(0).locator('.toggle').check();
+    await expect(todoItems).toHaveText([TODO_ITEMS[0], TODO_ITEMS[1]]);
+    await expect(todoItems).toHaveClass(['completed', '']);
+
+    // Ensure there is 1 completed item.
+    checkNumberOfCompletedTodosInLocalStorage(page, 1);
+
+    // Now reload.
+    await page.reload();
+    await expect(todoItems).toHaveText([TODO_ITEMS[0], TODO_ITEMS[1]]);
+    await expect(todoItems).toHaveClass(['completed', '']);
+  });
+});
+
+test.describe('Routing', () => {
+  test.beforeEach(async ({ page }) => {
+    await createDefaultTodos(page);
+    // make sure the app had a chance to save updated todos in storage
+    // before navigating to a new view, otherwise the items can get lost :(
+    // in some frameworks like Durandal
+    await checkTodosInLocalStorage(page, TODO_ITEMS[0]);
+  });
+
+  test('should allow me to display active items', async ({ page }) => {
+    await page.locator('.todo-list li .toggle').nth(1).check();
+    await checkNumberOfCompletedTodosInLocalStorage(page, 1);
+    await page.locator('.filters >> text=Active').click();
+    await expect(page.locator('.todo-list li')).toHaveCount(2);
+    await expect(page.locator('.todo-list li')).toHaveText([TODO_ITEMS[0], TODO_ITEMS[2]]);
+  });
+
+  test('should respect the back button', async ({ page }) => {
+    await page.locator('.todo-list li .toggle').nth(1).check();
+    await checkNumberOfCompletedTodosInLocalStorage(page, 1);
+
+    await test.step('Showing all items', async () => {
+      await page.locator('.filters >> text=All').click();
+      await expect(page.locator('.todo-list li')).toHaveCount(3);
+    });
+
+    await test.step('Showing active items', async () => {
+      await page.locator('.filters >> text=Active').click();
+    });
+
+    await test.step('Showing completed items', async () => {
+      await page.locator('.filters >> text=Completed').click();
+    });
+
+    await expect(page.locator('.todo-list li')).toHaveCount(1);
+    await page.goBack();
+    await expect(page.locator('.todo-list li')).toHaveCount(2);
+    await page.goBack();
+    await expect(page.locator('.todo-list li')).toHaveCount(3);
+  });
+
+  test('should allow me to display completed items', async ({ page }) => {
+    await page.locator('.todo-list li .toggle').nth(1).check();
+    await checkNumberOfCompletedTodosInLocalStorage(page, 1);
+    await page.locator('.filters >> text=Completed').click();
+    await expect(page.locator('.todo-list li')).toHaveCount(1);
+  });
+
+  test('should allow me to display all items', async ({ page }) => {
+    await page.locator('.todo-list li .toggle').nth(1).check();
+    await checkNumberOfCompletedTodosInLocalStorage(page, 1);
+    await page.locator('.filters >> text=Active').click();
+    await page.locator('.filters >> text=Completed').click();
+    await page.locator('.filters >> text=All').click();
+    await expect(page.locator('.todo-list li')).toHaveCount(3);
+  });
+
+  test('should highlight the currently applied filter', async ({ page }) => {
+    await expect(page.locator('.filters >> text=All')).toHaveClass('selected');
+    await page.locator('.filters >> text=Active').click();
+    // Page change - active items.
+    await expect(page.locator('.filters >> text=Active')).toHaveClass('selected');
+    await page.locator('.filters >> text=Completed').click();
+    // Page change - completed items.
+    await expect(page.locator('.filters >> text=Completed')).toHaveClass('selected');
+  });
+});
+
+async function createDefaultTodos(page: Page) {
+  for (const item of TODO_ITEMS) {
+    await page.locator('.new-todo').fill(item);
+    await page.locator('.new-todo').press('Enter');
+  }
+}
+
+async function checkNumberOfTodosInLocalStorage(page: Page, expected: number) {
+  return await page.waitForFunction(e => {
+    return JSON.parse(localStorage['react-todos']).length === e;
+  }, expected);
+}
+
+async function checkNumberOfCompletedTodosInLocalStorage(page: Page, expected: number) {
+  return await page.waitForFunction(e => {
+    return JSON.parse(localStorage['react-todos']).filter((todo: any) => todo.completed).length === e;
+  }, expected);
+}
+
+async function checkTodosInLocalStorage(page: Page, title: string) {
+  return await page.waitForFunction(t => {
+    return JSON.parse(localStorage['react-todos']).map((todo: any) => todo.title).includes(t);
+  }, title);
+}

tests/loadsite.spec.ts

@@ -0,0 +1,179 @@
+import { toBase64 } from 'js-base64';
+
+// describe('Site Loads', () => {
+// 	beforeEach(() => {
+// 		cy.clearLocalStorage();
+// 		cy.visit('/');
+// 	});
+
+// 	it('Check Home page load', () => {
+// 		cy.url().should('include', '/edit');
+// 		cy.contains('History').click();
+// 		cy.getLocalStorage('codeStore').snapshot();
+// 	});
+
+// 	it('Check Redirect from old URL', () => {
+// 		cy.visit(
+// 			'/#/edit/eyJjb2RlIjoiZ3JhcGggVERcbiAgICBBW0NocmlzdG1hc10gLS0-fEdldCBtb25leXwgQihHbyBzaG9wcGluZylcbiAgICBCIC0tPiBDe0xldCBtZSB0aGlua31cbiAgICBDIC0tPnxPbmV8IERbTGFwdG9wXVxuICAgIEMgLS0-fFR3b3wgRVtpUGhvbmVdXG4gICAgQyAtLT58VGhyZWV8IEZbZmE6ZmEtY2FyIENhcl0iLCJtZXJtYWlkIjp7InRoZW1lIjoiZGVmYXVsdCJ9LCJ1cGRhdGVFZGl0b3IiOmZhbHNlfQ'
+// 		);
+// 		cy.url().should('include', '/edit#pako:eNp');
+// 	});
+
+// 	it('should load sample diagrams when clicked', () => {
+// 		cy.contains('Sample Diagrams').click();
+// 		cy.contains('Pie').click();
+// 		cy.contains('pie title Pets adopted by volunteers');
+// 		cy.contains('Class').click();
+// 		cy.contains('classDiagram');
+// 	});
+
+// 	(Cypress.env('CI') === 'true' ? describe : describe.skip)('github', () => {
+// 		it('should load diagram from gist', () => {
+// 			cy.visit(`/edit?gist=https://gist.github.com/sidharthv96/6268a23e673a533dcb198f241fd7012a`);
+// 			cy.contains('History').click();
+// 			cy.contains('Go shopping!!');
+// 			cy.contains('Revisions');
+// 			cy.contains('sidharthv96 v8f8f1e2');
+// 			cy.contains('sidharthv96 v7851e19');
+// 			cy.getLocalStorage('codeStore').snapshot();
+// 		});
+
+// 		it('should load diagram from gist revision', () => {
+// 			cy.visit(
+// 				'/edit?gist=https://gist.github.com/sidharthv96/6268a23e673a533dcb198f241fd7012a/ec9b4ab0e41e4ff6287326cd3cb47affd7851e19'
+// 			);
+// 			cy.contains('History').click();
+// 			cy.contains('Party');
+// 			cy.contains('Revisions');
+// 			cy.contains('sidharthv96 v7851e19');
+// 			cy.getLocalStorage('codeStore').snapshot();
+// 		});
+
+// 		it('should load diagram from raw files', () => {
+// 			cy.visit(
+// 				'/edit?code=https://gist.githubusercontent.com/sidharthv96/6268a23e673a533dcb198f241fd7012a/raw/4eb03887e6a41397e80bdcdbf94017c498f8f1e2/code.mmd&config=https://gist.githubusercontent.com/sidharthv96/6268a23e673a533dcb198f241fd7012a/raw/4eb03887e6a41397e80bdcdbf94017c498f8f1e2/config.json'
+// 			);
+// 			cy.contains('Party');
+// 			cy.getLocalStorage('codeStore').snapshot();
+// 		});
+// 	});
+
+// 	// Disabled temporarily. Should be enabled after the issue is fixed in Mermaid.
+// 	// it('should prevent setting the "securityLevel" option via URL', () => {
+// 	// 	const b64State = toBase64(
+// 	// 		`{"code":"graph TD\\nA[\\"<img src='https://via.placeholder.com/64' width=64 />\\"]","mermaid":"{\\"securityLevel\\": \\"loose\\", \\"theme\\": \\"forest\\"}","autoSync":true,"updateDiagram":true}`,
+// 	// 		true
+// 	// 	);
+// 	// 	cy.on('window:confirm', () => true);
+// 	// 	cy.visit(`/edit#${b64State}`);
+// 	// 	cy.contains('Config').click();
+// 	// 	cy.contains('forest');
+// 	// 	cy.contains('securityLevel').should('not.exist');
+// 	// 	cy.get('#view').find('img').should('not.exist');
+// 	// 	cy.get('#view').contains('<img');
+// 	// 	cy.get('#view').contains(`src='https://via.placeholder.com/64'`);
+// 	// });
+
+// 	it.skip('should allow persisting "securityLevel" using confirm dialogue', () => {
+// 		const b64State = toBase64(
+// 			`{"code":"graph TD\\nA[\\"<img src='https://dummyimage.com/64' width=64/>\\"]","mermaid":"{\\"securityLevel\\": \\"loose\\", \\"theme\\": \\"forest\\"}","autoSync":true,"updateDiagram":true}`,
+// 			true
+// 		);
+// 		cy.on('window:confirm', () => false);
+// 		cy.visit(`/edit#${b64State}`);
+// 		cy.get('#editor').type(' ');
+// 		cy.contains('Config').click();
+// 		cy.contains('forest');
+// 		cy.contains('securityLevel');
+// 		cy.get('#view').find('img').should('be.visible');
+// 	});
+
+// 	it('should show troubleshooting steps if loading fails', () => {
+// 		cy.visit('/#/edit/eyJjb2RlIjoiZ3JhcGggVERcbiAg');
+// 		cy.reload(true);
+// 		cy.contains('Please Click here to Raise an issue in github.');
+// 	});
+
+// 	it('should load uncompressed URL', () => {
+// 		cy.visit(
+// 			'/edit/#eyJjb2RlIjoiZ3JhcGggVERcbiAgICBBW05ldyBZZWFyXSAtLT58R2V0IG1vbmV5fCBCKEdvIHNob3BwaW5nKVxuICAgIEIgLS0-IEN7TGV0IG1lIHRoaW5rfVxuICAgIEMgLS0-fE9uZXwgRFtMYXB0b3BdXG4gICAgQyAtLT58VHdvfCBFW2lQaG9uZV1cbiAgICBDIC0tPnxUaHJlZXwgRltmYTpmYS1jYXIgQ2FyXSIsIm1lcm1haWQiOiJ7XG4gIFwidGhlbWVcIjogXCJkZWZhdWx0XCJcbn0iLCJ1cGRhdGVFZGl0b3IiOmZhbHNlLCJhdXRvU3luYyI6dHJ1ZSwidXBkYXRlRGlhZ3JhbSI6ZmFsc2V9'
+// 		);
+// 		cy.contains('New Year');
+// 		cy.visit(
+// 			'/edit#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'
+// 		);
+// 		cy.contains('Animal');
+// 		cy.visit(
+// 			'/edit/#base64:eyJjb2RlIjoiZ3JhcGggVERcbiAgICBBW05ldyBZZWFyXSAtLT58R2V0IG1vbmV5fCBCKEdvIHNob3BwaW5nKVxuICAgIEIgLS0-IEN7TGV0IG1lIHRoaW5rfVxuICAgIEMgLS0-fE9uZXwgRFtMYXB0b3BdXG4gICAgQyAtLT58VHdvfCBFW2lQaG9uZV1cbiAgICBDIC0tPnxUaHJlZXwgRltmYTpmYS1jYXIgQ2FyXSIsIm1lcm1haWQiOiJ7XG4gIFwidGhlbWVcIjogXCJkZWZhdWx0XCJcbn0iLCJ1cGRhdGVFZGl0b3IiOmZhbHNlLCJhdXRvU3luYyI6dHJ1ZSwidXBkYXRlRGlhZ3JhbSI6ZmFsc2V9'
+// 		);
+// 		cy.contains('New Year');
+// 	});
+
+// 	it('should load compressed URL', () => {
+// 		cy.visit(
+// 			'/edit#pako:eNpVkM2KwkAQhF-l6dMK5gVyEDRxvYi7sF6WjIcm0zqDzg_jBJEk725Hd2G3Tw31VVFUj23QjCWeEkUD-1p5kFs2O77BN1M6QFEshg1ncMHzfYDV2ybA1YQYrT_NXvhqgqDqtxPGkI315_ElVU__h-cB6mZLMYd4-Kvsb2GAdWM_jcT_V0xicb03RyqPVLSUoJI-OEfHyZHV0rqfDAqzYccKS3k1pbNC5Ufhuqgp81rbHBJKxuXKc6Quh6-7b7HMqeNfqLYkC7gfanwAlW1ZvQ'
+// 		);
+// 		cy.contains('New Year');
+// 		cy.visit(
+// 			'/edit#pako:eNptkU1PwzAMhv9K5BOI9Q9EXBDbJA477YYqITcxndV8QD40weh_Jy1rGR0-OY_tV2_sEyivCSQogzGuGduAtnaixINji0bcf1WVWGfVXdMtx8M1faYm4B8sxR27JLClJd6nwK4VLTlN4bI4jMQd2pLe3C4KFhNNcLQ92jv9ADGLNoTdozc-zIV4ZDsNlud7RtVN7_5Sb_jYrFcN3iN_0pPbEqUZK3QbTP_Ojyv4NdR4bwTHlyMbPcOQ3WJ2CliBpWCRdbnLqFJDOpClGmRJNYauhtr1pS-_6bKMjebkA8hXNJFWgDn5_YdTIFPINDWdb3vu6r8BaWOZRQ'
+// 		);
+// 		cy.contains('Animal');
+// 	});
+// });
+
+import { test, expect } from '@playwright/test';
+
+test.describe('site loads', () => {
+  test.beforeEach(async ({ page }) => {
+    await page.addInitScript(() => {
+      window.localStorage.clear();
+    });
+    await page.goto('/', { waitUntil: 'networkidle' });
+  });
+
+  test('should load home page', async ({ page }) => {
+    expect(page.url()).toContain('/edit');
+    await expect(page.locator('"History"')).toBeVisible();
+    // const { origins } = await context.storageState();
+    // console.log(JSON.stringify(origins));
+    // expect(JSON.stringify(origins)).toMatchSnapshot('initial-storage-state.json');
+  });
+
+  test('should redirect from old URL', async ({ page }) => {
+    // Note that Promise.all prevents a race condition
+    // between clicking and waiting for a navigation.
+    await Promise.all([
+      page.waitForNavigation({ url: '**/edit#pako:eNp**', timeout: 1000 }),
+      page.goto(
+        '/#/edit/eyJjb2RlIjoiZ3JhcGggVERcbiAgICBBW0NocmlzdG1hc10gLS0-fEdldCBtb25leXwgQihHbyBzaG9wcGluZylcbiAgICBCIC0tPiBDe0xldCBtZSB0aGlua31cbiAgICBDIC0tPnxPbmV8IERbTGFwdG9wXVxuICAgIEMgLS0-fFR3b3wgRVtpUGhvbmVdXG4gICAgQyAtLT58VGhyZWV8IEZbZmE6ZmEtY2FyIENhcl0iLCJtZXJtYWlkIjp7InRoZW1lIjoiZGVmYXVsdCJ9LCJ1cGRhdGVFZGl0b3IiOmZhbHNlfQ'
+      )
+    ]);
+    expect(page.url()).toContain('/edit#pako:eNp');
+  });
+
+  test('should load sample diagrams when clicked', async ({ page }) => {
+    await page.click('"Sample Diagrams"');
+    await page.click('"Pie"');
+    await expect(page.locator('"pie title Pets adopted by volunteers"')).toBeVisible();
+    await page.click('"Class"');
+    await expect(page.locator('"classDiagram"')).toBeVisible();
+  });
+});
+// test('homepage has Playwright in title and get started link linking to the intro page', async ({
+// 	page,
+// 	context
+// }) => {
+// 	await page.goto(
+// 		'http://localhost:3000/edit?gist=https://gist.github.com/sidharthv96/6268a23e673a533dcb198f241fd7012a/ec9b4ab0e41e4ff6287326cd3cb47affd7851e19'
+// 	);
+
+// 	// cy.getLocalStorage('codeStore').snapshot();
+// 	// Expect a title "to contain" a substring.
+// 	await page.locator('"History"').click();
+// 	await page.locator('"Party"').isVisible();
+// 	await page.locator('"Revisions"').isVisible();
+// 	await page.locator('"sidharthv96 v7851e19"').isVisible();
+// 	await page.waitForTimeout(400);
+// 	const storage = await context.storageState();
+// 	expect(JSON.stringify(storage)).toMatchSnapshot();
+// });

tests/loadsite.spec.ts-snapshots/initial-storage-state-chromium-darwin.json

@@ -0,0 +1,17 @@
+[
+  {
+    "origin": "http://localhost:3000",
+    "localStorage": [
+      { "name": "__anon_id", "value": "\"87f53493-b439-425c-961c-9a2014f0ced8\"" },
+      { "name": "manualHistoryStore", "value": "[]" },
+      { "name": "autoHistoryMode", "value": "\"manual\"" },
+      {
+        "name": "codeStore",
+        "value": "{\"code\":\"graph TD\\n    A[Christmas] -->|Get money| B(Go shopping)\\n    B --> C{Let me think}\\n    C -->|One| D[Laptop]\\n    C -->|Two| E[iPhone]\\n    C -->|Three| F[fa:fa-car Car]\\n  \",\"mermaid\":\"{\\n  \\\"theme\\\": \\\"default\\\"\\n}\",\"autoSync\":true,\"updateDiagram\":true}"
+      },
+      { "name": "migrations", "value": "{\"version\":0}" },
+      { "name": "themeStore", "value": "{\"theme\":\"light\",\"isDark\":false}" },
+      { "name": "autoHistoryStore", "value": "[]" }
+    ]
+  }
+]

tests/loadsite.spec.ts-snapshots/site-loads-Check-Home-page-load-1-chromium-darwin.txt

@@ -0,0 +1 @@
+[{"origin":"http://localhost:3000","localStorage":[{"name":"__anon_id","value":"\"e4127e54-eced-443f-837e-0986e577b624\""},{"name":"manualHistoryStore","value":"[]"},{"name":"autoHistoryMode","value":"\"manual\""},{"name":"codeStore","value":"{\"code\":\"graph TD\\n    A[Christmas] -->|Get money| B(Go shopping)\\n    B --> C{Let me think}\\n    C -->|One| D[Laptop]\\n    C -->|Two| E[iPhone]\\n    C -->|Three| F[fa:fa-car Car]\\n  \",\"mermaid\":\"{\\n  \\\"theme\\\": \\\"default\\\"\\n}\",\"autoSync\":true,\"updateDiagram\":true}"},{"name":"migrations","value":"{\"version\":0}"},{"name":"themeStore","value":"{\"theme\":\"light\",\"isDark\":false}"},{"name":"autoHistoryStore","value":"[]"}]}]

tsconfig.json

@@ -6,12 +6,17 @@
     "cypress/**/*.ts",
     "cypress/**/*.js",
     "cypress/**/*.json",
+    "tests/**/*.ts",
+    "tests/**/*.js",
+    "tests/**/*.json",
     "static/**/*.js",
-    "static/**/*.json"
+    "static/**/*.json",
+    "./playwright.config.ts"
   ],
   "compilerOptions": {
     "resolveJsonModule": true,
     "allowSyntheticDefaultImports": true,
+    "strictNullChecks": true,
     "types": ["vitest/importMeta"]
   },
   "extends": "./.svelte-kit/tsconfig.json"