test: add SW routing tests covering font-interception crash prevention

Documents the fetch routing rules in public/sw.js that prevent the
OnlyOffice v7.5 units_per_EM crash:
- Font files (.ttf/.woff/.woff2/.otf/.eot) must bypass the SW to avoid
  added latency that triggers Chrome's font-loading intervention
- Document URLs (?src=, ?file=) bypass the cache to stay fresh
- Cross-origin and non-GET requests are not intercepted

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: chaxus

test/unit/sw-routing.test.ts

@@ -0,0 +1,110 @@
+/**
+ * Tests for the fetch routing rules in public/sw.js.
+ *
+ * sw.js is a non-module service worker file that can't be imported directly,
+ * so we replicate the routing conditions here as a living specification.
+ * If sw.js changes, update both files together.
+ *
+ * The rules guard against two classes of bug found in this project:
+ *   - Font files intercepted by SW → added latency → Chrome "Slow Network"
+ *     intervention → OnlyOffice v7.5 fallback font crash (units_per_EM)
+ *   - Document URLs cached by SW → stale content served to editor
+ */
+
+import { describe, expect, it } from 'vitest';
+
+const FONT_REGEX = /\.(ttf|woff2?|otf|eot)(\?.*)?$/;
+
+const ORIGIN = 'http://localhost:5173';
+
+function swShouldHandle(method: string, urlStr: string): boolean {
+  if (method !== 'GET') return false;
+  const url = new URL(urlStr);
+  if (url.origin !== ORIGIN) return false;
+  if (url.searchParams.has('file') || url.searchParams.has('src')) return false;
+  if (FONT_REGEX.test(url.pathname)) return false;
+  return true;
+}
+
+describe('SW fetch routing', () => {
+  describe('non-GET requests are not handled', () => {
+    it.each(['POST', 'PUT', 'DELETE', 'PATCH'])('%s', (method) => {
+      expect(swShouldHandle(method, `${ORIGIN}/index.html`)).toBe(false);
+    });
+  });
+
+  describe('cross-origin requests are not handled', () => {
+    it('skips external document URL', () => {
+      expect(swShouldHandle('GET', 'https://example.com/doc.docx')).toBe(false);
+    });
+
+    it('skips CDN asset', () => {
+      expect(swShouldHandle('GET', 'https://cdn.example.com/font.ttf')).toBe(false);
+    });
+  });
+
+  describe('document query params bypass the SW cache', () => {
+    it('skips ?src= URLs', () => {
+      expect(swShouldHandle('GET', `${ORIGIN}/?src=https://example.com/doc.docx`)).toBe(false);
+    });
+
+    it('skips ?file= URLs', () => {
+      expect(swShouldHandle('GET', `${ORIGIN}/?file=report.xlsx`)).toBe(false);
+    });
+
+    it('skips URL with both src and other params', () => {
+      expect(swShouldHandle('GET', `${ORIGIN}/?src=doc.docx&readonly=true`)).toBe(false);
+    });
+  });
+
+  describe('font files are not intercepted (crash prevention)', () => {
+    // Intercepting font files adds SW latency which triggers Chrome's
+    // "Slow Network" font-loading intervention. OnlyOffice v7.5 then
+    // crashes with "Cannot read properties of undefined (reading 'units_per_EM')"
+    // in the fallback font code path of slide/word/cell sdk-all.js.
+    it.each([
+      ['/web-apps/apps/common/main/resources/font/ASC.ttf', '.ttf (OnlyOffice internal font)'],
+      ['/fonts/NotoSansTC-VF.ttf', '.ttf (CJK fallback font)'],
+      ['/fonts/LiberationSans-Bold.woff2', '.woff2'],
+      ['/fonts/arial.woff', '.woff'],
+      ['/fonts/symbol.otf', '.otf'],
+      ['/fonts/legacy.eot', '.eot'],
+      ['/fonts/font.ttf?v=123', '.ttf with query string'],
+    ])('%s (%s)', (pathname) => {
+      expect(swShouldHandle('GET', `${ORIGIN}${pathname}`)).toBe(false);
+    });
+  });
+
+  describe('font regex matches extensions correctly', () => {
+    it.each(['.ttf', '.woff', '.woff2', '.otf', '.eot'])('matches %s', (ext) => {
+      expect(FONT_REGEX.test(`/fonts/file${ext}`)).toBe(true);
+    });
+
+    it('does not match .ttfx', () => {
+      expect(FONT_REGEX.test('/fonts/file.ttfx')).toBe(false);
+    });
+
+    it('does not match .js or .css', () => {
+      expect(FONT_REGEX.test('/sdk-all.js')).toBe(false);
+      expect(FONT_REGEX.test('/styles.css')).toBe(false);
+    });
+
+    it('matches font extensions embedded in longer paths', () => {
+      expect(FONT_REGEX.test('/web-apps/apps/common/main/resources/font/ASC.ttf')).toBe(true);
+    });
+  });
+
+  describe('same-origin static assets are handled', () => {
+    it.each([
+      `${ORIGIN}/index.html`,
+      `${ORIGIN}/`,
+      `${ORIGIN}/web-apps/apps/api/documents/api.js`,
+      `${ORIGIN}/public/sdkjs/slide/sdk-all.js`,
+      `${ORIGIN}/styles/base.css`,
+      `${ORIGIN}/manifest.json`,
+      `${ORIGIN}/img/64.png`,
+    ])('%s', (url) => {
+      expect(swShouldHandle('GET', url)).toBe(true);
+    });
+  });
+});