fix(coverage): exclude vite virtual modules by default (#3794)

docs/config/index.md

@@ -723,6 +723,9 @@ List of files included in coverage as glob patterns
   'dist/**',
   'packages/*/test?(s)/**',
   '**/*.d.ts',
+  '**/virtual:*',
+  '**/__x00__*',
+  '**/\x00*',
   'cypress/**',
   'test?(s)/**',
   'test?(-*).?(c|m)[jt]s?(x)',

packages/vitest/src/defaults.ts

@@ -15,6 +15,9 @@ const defaultCoverageExcludes = [
   'dist/**',
   'packages/*/test?(s)/**',
   '**/*.d.ts',
+  '**/virtual:*',
+  '**/__x00__*',
+  '**/\x00*',
   'cypress/**',
   'test?(s)/**',
   'test?(-*).?(c|m)[jt]s?(x)',

test/coverage-test/coverage-report-tests/generic.report.test.ts

@@ -101,3 +101,19 @@ test('coverage provider does not conflict with built-in reporter\'s outputFile',
 
   expect(files).toContain('junit.xml')
 })
+
+test('virtual files should be excluded', () => {
+  const files = fs.readdirSync(resolve('./coverage'))
+  const srcFiles = fs.readdirSync(resolve('./coverage/src'))
+
+  for (const file of [...files, ...srcFiles]) {
+    expect(file).not.toContain('virtual:')
+
+    // Vitest in node
+    expect(file).not.toContain('__x00__')
+    expect(file).not.toContain('\0')
+
+    // Vitest browser
+    expect(file).not.toContain('\x00')
+  }
+})

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

@@ -1,9 +1,16 @@
 import { expect, test } from 'vitest'
+
+// @ts-expect-error -- untyped virtual file provided by custom plugin
+import virtualFile1 from 'virtual:vitest-custom-virtual-file-1'
+
 import { implicitElse } from '../src/implicitElse'
 import { useImportEnv } from '../src/importEnv'
 import { second } from '../src/function-count'
 import { runDynamicFileCJS, runDynamicFileESM } from '../src/dynamic-files'
 
+// @ts-expect-error -- untyped virtual file provided by custom plugin
+import virtualFile2 from '\0vitest-custom-virtual-file-2'
+
 // Browser mode crashes with dynamic files. Enable this when browser mode works.
 // To keep istanbul report consistent between browser and node, skip dynamic tests when istanbul is used.
 const skipDynamicFiles = globalThis.process?.env.COVERAGE_PROVIDER === 'istanbul' || !globalThis.process?.env.COVERAGE_PROVIDER
@@ -40,3 +47,8 @@ test.skipIf(skipDynamicFiles)('run dynamic ESM file', async () => {
 test.skipIf(skipDynamicFiles)('run dynamic CJS file', async () => {
   await runDynamicFileCJS()
 })
+
+test('virtual file imports', () => {
+  expect(virtualFile1).toBe('This file should be excluded from coverage report #1')
+  expect(virtualFile2).toBe('This file should be excluded from coverage report #2')
+})

test/coverage-test/vitest.config.ts

@@ -7,6 +7,33 @@ const provider = process.argv[1 + process.argv.indexOf('--provider')]
 export default defineConfig({
   plugins: [
     vue(),
+    {
+      // Simulates Vite's virtual files: https://vitejs.dev/guide/api-plugin.html#virtual-modules-convention
+      name: 'vitest-custom-virtual-files',
+      resolveId(id) {
+        if (id === 'virtual:vitest-custom-virtual-file-1')
+          return 'src/virtual:vitest-custom-virtual-file-1.ts'
+
+        if (id === '\0vitest-custom-virtual-file-2')
+          return 'src/\0vitest-custom-virtual-file-2.ts'
+      },
+      load(id) {
+        if (id === 'src/virtual:vitest-custom-virtual-file-1.ts') {
+          return `
+            const virtualFile = "This file should be excluded from coverage report #1"
+            export default virtualFile;
+          `
+        }
+
+        // Vitest browser resolves this as "\x00", Node as "__x00__"
+        if (id === 'src/__x00__vitest-custom-virtual-file-2.ts' || id === 'src/\x00vitest-custom-virtual-file-2.ts') {
+          return `
+            const virtualFile = "This file should be excluded from coverage report #2"
+            export default virtualFile;
+          `
+        }
+      },
+    },
   ],
   define: {
     MY_CONSTANT: '"my constant"',