Merge pull request #795 from mvanhorn/fix/662-map-upsert-polyfill

fix: polyfill Map.prototype.getOrInsertComputed to stop PDF.js render crash

src/tests/map-upsert-polyfill.test.ts

@@ -0,0 +1,121 @@
+import { readFileSync } from 'node:fs';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+type MapWithUpsert<K, V> = Map<K, V> & {
+  getOrInsert(key: K, value: V): V;
+  getOrInsertComputed(key: K, callback: (key: K) => V): V;
+};
+
+const getOrInsertDescriptor = Object.getOwnPropertyDescriptor(
+  Map.prototype,
+  'getOrInsert'
+);
+const getOrInsertComputedDescriptor = Object.getOwnPropertyDescriptor(
+  Map.prototype,
+  'getOrInsertComputed'
+);
+
+const restoreMethod = (
+  name: 'getOrInsert' | 'getOrInsertComputed',
+  descriptor: PropertyDescriptor | undefined
+) => {
+  if (descriptor) {
+    Object.defineProperty(Map.prototype, name, descriptor);
+  } else {
+    Reflect.deleteProperty(Map.prototype, name);
+  }
+};
+
+const importPolyfill = async () => {
+  await import('../js/utils/map-upsert-polyfill');
+};
+
+describe('Map upsert polyfill', () => {
+  beforeEach(() => {
+    vi.resetModules();
+  });
+
+  afterEach(() => {
+    restoreMethod('getOrInsert', getOrInsertDescriptor);
+    restoreMethod('getOrInsertComputed', getOrInsertComputedDescriptor);
+    vi.resetModules();
+  });
+
+  it('preserves an existing native implementation', async () => {
+    const nativeImplementation = vi.fn();
+    Object.defineProperty(Map.prototype, 'getOrInsertComputed', {
+      configurable: true,
+      writable: true,
+      value: nativeImplementation,
+    });
+
+    await importPolyfill();
+
+    expect(
+      Object.getOwnPropertyDescriptor(Map.prototype, 'getOrInsertComputed')
+        ?.value
+    ).toBe(nativeImplementation);
+  });
+
+  it('installs getOrInsertComputed when it is missing', async () => {
+    Reflect.deleteProperty(Map.prototype, 'getOrInsertComputed');
+
+    await importPolyfill();
+
+    const descriptor = Object.getOwnPropertyDescriptor(
+      Map.prototype,
+      'getOrInsertComputed'
+    );
+    expect(typeof descriptor?.value).toBe('function');
+    expect(descriptor?.enumerable).toBe(false);
+  });
+
+  it('returns an existing value without invoking the callback', async () => {
+    Reflect.deleteProperty(Map.prototype, 'getOrInsertComputed');
+    await importPolyfill();
+    const map = new Map([['key', 'cached']]) as MapWithUpsert<string, string>;
+    const callback = vi.fn(() => 'computed');
+
+    expect(map.getOrInsertComputed('key', callback)).toBe('cached');
+    expect(callback).not.toHaveBeenCalled();
+  });
+
+  it('computes, stores, and returns a missing value', async () => {
+    Reflect.deleteProperty(Map.prototype, 'getOrInsertComputed');
+    await importPolyfill();
+    const map = new Map<string, string>() as MapWithUpsert<string, string>;
+    const callback = vi.fn((key: string) => `${key}-value`);
+
+    expect(map.getOrInsertComputed('missing', callback)).toBe('missing-value');
+    expect(callback).toHaveBeenCalledOnce();
+    expect(callback).toHaveBeenCalledWith('missing');
+    expect(map.get('missing')).toBe('missing-value');
+  });
+
+  it('installs getOrInsert with matching get-or-insert behavior', async () => {
+    Reflect.deleteProperty(Map.prototype, 'getOrInsert');
+    await importPolyfill();
+    const map = new Map([['existing', 'cached']]) as MapWithUpsert<
+      string,
+      string
+    >;
+
+    expect(map.getOrInsert('existing', 'replacement')).toBe('cached');
+    expect(map.getOrInsert('missing', 'inserted')).toBe('inserted');
+    expect(map.get('missing')).toBe('inserted');
+  });
+
+  it('loads before PDF.js so render can use the methods', () => {
+    const mainSource = readFileSync(
+      new URL('../js/main.ts', import.meta.url),
+      'utf8'
+    );
+    const polyfillImport = "import './utils/map-upsert-polyfill.js';";
+    const pdfjsImport = "import * as pdfjsLib from 'pdfjs-dist';";
+
+    expect(mainSource.startsWith(polyfillImport)).toBe(true);
+    expect(mainSource.indexOf(polyfillImport)).toBeLessThan(
+      mainSource.indexOf(pdfjsImport)
+    );
+  });
+});