fix(coverage): v8 browser memory leak between test files (#11466)

Author: AriPerkkio

packages/coverage-v8/src/browser.ts

@@ -23,8 +23,12 @@ const mod: CoverageProviderModule = {
     return triggerCommand('__vitest_takeV8Coverage', [window.location.href])
   },
 
-  stopCoverage() {
-    // Browser mode should not stop coverage as same V8 instance is shared between tests
+  async stopCoverage({ isolate }) {
+    if (isolate === false) {
+      return
+    }
+
+    await triggerCommand('__vitest_stopV8Coverage')
   },
 
   async getProvider(): Promise<V8CoverageProvider> {

packages/coverage-v8/src/commands.ts

@@ -9,17 +9,28 @@ import { resolve } from 'pathe'
 export const commands: Record<string, BrowserCommand<any[]>> = {
   startV8Coverage,
   takeV8Coverage,
+  stopV8Coverage,
 }
 
 async function startV8Coverage(context: BrowserCommandContext): Promise<void> {
   const session: CDPSession = await context.__ensureCDPHandler()
+
+  // Previous test file's modules must be collected, otherwise V8 reuses their compiled code without block coverage
+  await session.send('HeapProfiler.collectGarbage')
+
   await session.send('Profiler.enable')
   await session.send('Profiler.startPreciseCoverage', {
     callCount: true,
     detailed: true,
   })
 }
 
+async function stopV8Coverage(context: BrowserCommandContext): Promise<void> {
+  const session: CDPSession = await context.__ensureCDPHandler()
+  await session.send('Profiler.stopPreciseCoverage')
+  await session.send('Profiler.disable')
+}
+
 async function takeV8Coverage(context: BrowserCommandContext, pageUrl: string): Promise<string> {
   const session: CDPSession = await context.__ensureCDPHandler()
   const coverage = await session.send('Profiler.takePreciseCoverage')

test/coverage-test/fixtures/test/memory-leak-1-fixture.test.ts

@@ -0,0 +1,6 @@
+import { test } from "vitest";
+import { commands } from "vitest/browser";
+
+test("report live documents", async () => {
+  await (commands as any).countLiveDocuments();
+});

test/coverage-test/fixtures/test/memory-leak-2-fixture.test.ts

@@ -0,0 +1,6 @@
+import { test } from "vitest";
+import { commands } from "vitest/browser";
+
+test("report live documents", async () => {
+  await (commands as any).countLiveDocuments();
+});

test/coverage-test/fixtures/test/memory-leak-3-fixture.test.ts

@@ -0,0 +1,6 @@
+import { test } from "vitest";
+import { commands } from "vitest/browser";
+
+test("report live documents", async () => {
+  await (commands as any).countLiveDocuments();
+});

test/coverage-test/fixtures/test/memory-leak-4-fixture.test.ts

@@ -0,0 +1,6 @@
+import { test } from "vitest";
+import { commands } from "vitest/browser";
+
+test("report live documents", async () => {
+  await (commands as any).countLiveDocuments();
+});

test/coverage-test/test/isolation.test.ts

@@ -56,6 +56,38 @@ for (const isolate of [true, false]) {
   }
 }
 
+/*
+ * This is mostly relevant for V8 provider which enables Profiler,
+ * but we'll test Istanbul too.
+ */
+test('browser mode tab isolation (#11447)', async ({ skip }) => {
+  skip(process.env.COVERAGE_BROWSER !== 'true', 'only relevant for browser mode')
+
+  const liveDocuments: number[] = []
+
+  await runVitest({
+    include: ['fixtures/test/memory-leak-*-fixture.test.ts'],
+    fileParallelism: false,
+    coverage: { reporter: 'json' },
+    browser: {
+      commands: {
+        async countLiveDocuments(context) {
+          const session = await context.page.context().newCDPSession(context.page)
+          await session.send('HeapProfiler.collectGarbage')
+
+          const { documents } = await session.send('Memory.getDOMCounters')
+          liveDocuments.push(documents)
+
+          await session.detach()
+        },
+      },
+    },
+  })
+
+  expect(liveDocuments).toHaveLength(4)
+  expect(new Set(liveDocuments).size).toBe(1)
+})
+
 class Sorter {
   sort(files: TestSpecification[]) {
     return files.sort((a) => {