From e30dd9cf692ede7bc62d1cbdb5732f513a85e001 Mon Sep 17 00:00:00 2001
From: innoprej <273227832+innoprej@users.noreply.github.com>
Date: Mon, 1 Jun 2026 22:24:13 +0900
Subject: [PATCH] fix(coverage): avoid matching sibling project roots (#10311)
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Co-authored-by: Shin JaeHee <jaeheesin@gmail.com>
Co-authored-by: Ari Perkkiö <ari.perkkio@gmail.com>
---
 packages/vitest/src/node/coverage.ts              |  5 +++--
 .../test/include-exclude.unit.test.ts             | 15 ++++++++++++++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/packages/vitest/src/node/coverage.ts b/packages/vitest/src/node/coverage.ts
index f17a15f8d..c8f8fdf40 100644
--- a/packages/vitest/src/node/coverage.ts
+++ b/packages/vitest/src/node/coverage.ts
@@ -156,14 +156,15 @@ export class BaseCoverageProvider {
       return cacheHit
     }
 
+    const matchingRoot = roots.find(root => filename.startsWith(`${slash(root)}/`) || filename === slash(root))
+
     // File outside project root with default allowExternal
-    if (this.options.allowExternal === false && roots.every(root => !filename.startsWith(root))) {
+    if (this.options.allowExternal === false && !matchingRoot) {
       this.globCache.set(filename, false)
 
       return false
     }
 
-    const matchingRoot = roots.find(root => filename.startsWith(`${slash(root)}/`) || filename === slash(root))
     const relativeFilename = matchingRoot ? relative(matchingRoot, filename) : filename
 
     if (pm.isMatch(relativeFilename, this.options.exclude, { dot: true })) {
diff --git a/test/coverage-test/test/include-exclude.unit.test.ts b/test/coverage-test/test/include-exclude.unit.test.ts
index 333aa850a..67d4411ef 100644
--- a/test/coverage-test/test/include-exclude.unit.test.ts
+++ b/test/coverage-test/test/include-exclude.unit.test.ts
@@ -144,10 +144,23 @@ test('files outside project when allowExternal: true', async () => {
   expect(isIncluded(resolve(process.cwd(), '../../package-b/src/two.ts'))).toBe(false)
 })
 
-async function init(options: Partial<CoverageOptions> & { testInclude?: string[] }) {
+test('files with almost matching name, outside project when allowExternal: false', async () => {
+  const isIncluded = await init({
+    include: ['**/*.ts'],
+    root: './something/',
+    allowExternal: false,
+  })
+
+  expect(isIncluded(resolve(process.cwd(), './something/src/one.ts'))).toBe(true)
+  expect(isIncluded(resolve(process.cwd(), './not-something/src/two.ts'))).toBe(false)
+  expect(isIncluded(resolve(process.cwd(), './something-else/src/three.ts'))).toBe(false)
+})
+
+async function init(options: Partial<CoverageOptions> & { testInclude?: string[]; root?: string }) {
   const vitest = await createVitest('test', {
     config: false,
     include: ['dont-match-anything', ...(options.testInclude || [])],
+    root: options.root,
     coverage: {
       ...options,
       enabled: true,
-- 
2.51.2