fix(trace viewer): prevent stale content for resource overrides

packages/playwright-core/src/utils/isomorphic/trace/snapshotServer.ts

@@ -104,7 +104,10 @@ export class SnapshotServer {
     headers.set('Access-Control-Allow-Origin', '*');
     headers.delete('Content-Length');
     headers.set('Content-Length', String(content.size));
-    headers.set('Cache-Control', 'public, max-age=31536000');
+    if (this._snapshotStorage.hasResourceOverride(resource.request.url))
+      headers.set('Cache-Control', 'no-store, no-cache, max-age=0');
+    else
+      headers.set('Cache-Control', 'public, max-age=31536000');
     const { status } = resource.response;
     const isNullBodyStatus = status === 101 || status === 204 || status === 205 || status === 304;
     return new Response(isNullBodyStatus ? null : content, {

packages/playwright-core/src/utils/isomorphic/trace/snapshotStorage.ts

@@ -28,6 +28,7 @@ export class SnapshotStorage {
   }>();
   private _cache = new LRUCache<SnapshotRenderer, string>(100_000_000);  // 100MB per each trace
   private _contextToResources = new Map<string, ResourceSnapshot[]>();
+  private _resourceUrlsWithOverrides = new Set<string>();
 
   addResource(contextId: string, resource: ResourceSnapshot): void {
     resource.request.url = rewriteURLForCustomProtocol(resource.request.url);
@@ -67,6 +68,18 @@ export class SnapshotStorage {
     // Resources are not necessarily sorted in the trace file, so sort them now.
     for (const resources of this._contextToResources.values())
       resources.sort((a, b) => (a._monotonicTime || 0) - (b._monotonicTime || 0));
+    // Resources that have overrides should not be cached, otherwise we might get stale content
+    // while serving snapshots with different override values.
+    for (const frameSnapshots of this._frameSnapshots.values()) {
+      for (const snapshot of frameSnapshots.raw) {
+        for (const override of snapshot.resourceOverrides)
+          this._resourceUrlsWithOverrides.add(override.url);
+      }
+    }
+  }
+
+  hasResourceOverride(url: string) {
+    return this._resourceUrlsWithOverrides.has(url);
   }
 
   private _ensureResourcesForContext(contextId: string): ResourceSnapshot[] {

tests/library/trace-viewer.spec.ts

@@ -2129,3 +2129,42 @@ test('should not navigate on anchor clicks', async ({ runAndTrace, page, server
   await checkLink('link2');
   await checkLink('link3');
 });
+
+test('should respect CSSOM changes', async ({ runAndTrace, page, server }) => {
+  const traceViewer = await runAndTrace(async () => {
+    await page.setContent('<style>button { color: red; }</style><button>Hello</button>');
+    await page.evaluate(() => { (document.styleSheets[0].cssRules[0] as any).style.color = 'blue'; });
+
+    await page.setContent('<style>@media { button { color: red; } }</style><button>Hello</button>');
+    await page.evaluate(() => {
+      window['rule'] = document.styleSheets[0].cssRules[0];
+      void 0;
+    });
+    await page.evaluate(() => { window['rule'].cssRules[0].style.color = 'black'; });
+    await page.evaluate(() => { window['rule'].insertRule('button:not(.disabled) { color: green; }', 1); });
+
+    await page.route('**/style.css', route => {
+      route.fulfill({ body: 'button { color: red; }', }).catch(() => {});
+    });
+    await page.goto(server.EMPTY_PAGE);
+    await page.setContent('<link rel="stylesheet" href="style.css"><button>Hello</button>');
+    await page.evaluate(() => { (document.styleSheets[0].cssRules[0] as any).style.color = 'blue'; });
+  });
+
+  const frame1 = await traceViewer.snapshotFrame('Set content', 0);
+  await expect(frame1.locator('button')).toHaveCSS('color', 'rgb(255, 0, 0)');
+  const frame2 = await traceViewer.snapshotFrame('Evaluate', 0);
+  await expect(frame2.locator('button')).toHaveCSS('color', 'rgb(0, 0, 255)');
+
+  const frame3 = await traceViewer.snapshotFrame('Set content', 1);
+  await expect(frame3.locator('button')).toHaveCSS('color', 'rgb(255, 0, 0)');
+  const frame4 = await traceViewer.snapshotFrame('Evaluate', 2);
+  await expect(frame4.locator('button')).toHaveCSS('color', 'rgb(0, 0, 0)');
+  const frame5 = await traceViewer.snapshotFrame('Evaluate', 3);
+  await expect(frame5.locator('button')).toHaveCSS('color', 'rgb(0, 128, 0)');
+
+  const frame6 = await traceViewer.snapshotFrame('Set content', 2);
+  await expect(frame6.locator('button')).toHaveCSS('color', 'rgb(255, 0, 0)');
+  const frame7 = await traceViewer.snapshotFrame('Evaluate', 4);
+  await expect(frame7.locator('button')).toHaveCSS('color', 'rgb(0, 0, 255)');
+});