fix(coverage): infer transform mode for uncovered files

packages/vitest/src/node/coverage.ts

@@ -634,15 +634,16 @@ export class BaseCoverageProvider<Options extends ResolvedCoverageOptions<'istan
         root: project.config.root,
         isBrowserEnabled: project.isBrowserEnabled(),
         vite: project.vite,
+        environment: project.config.environment,
       })),
       // Check core last as it will match all files anyway
-      { root: ctx.config.root, vite: ctx.vite, isBrowserEnabled: ctx.getRootProject().isBrowserEnabled() },
+      { root: ctx.config.root, vite: ctx.vite, isBrowserEnabled: ctx.getRootProject().isBrowserEnabled(), environment: ctx.config.environment },
     ]
 
     return async function transformFile(filename: string): Promise<TransformResult | null | undefined> {
       let lastError
 
-      for (const { root, vite, isBrowserEnabled } of servers) {
+      for (const { root, vite, isBrowserEnabled, environment } of servers) {
         // On Windows root doesn't start with "/" while filenames do
         if (!filename.startsWith(root) && !filename.startsWith(`/${root}`)) {
           continue
@@ -657,14 +658,18 @@ export class BaseCoverageProvider<Options extends ResolvedCoverageOptions<'istan
         }
 
         try {
+          if (environment === 'jsdom' || environment === 'happy-dom') {
+            return await vite.environments.client.transformRequest(filename)
+          }
+
           return await vite.environments.ssr.transformRequest(filename)
         }
         catch (error) {
           lastError = error
         }
       }
 
-      // All vite-node servers failed to transform the file
+      // All vite servers failed to transform the file
       throw lastError
     }
   }

test/coverage-test/fixtures/configs/vitest.config.conditional.ts

@@ -1,4 +1,4 @@
-import { join, resolve } from 'node:path'
+import { resolve } from 'node:path'
 import { defineConfig } from 'vitest/config'
 
 export default defineConfig({
@@ -9,9 +9,9 @@ export default defineConfig({
         replacement: "$1",
         customResolver(_, __, options) {
           if ('ssr' in options && options.ssr) {
-            return { id: resolve('fixtures/src/conditional/node.ts') }
+            return { id: resolve('fixtures/src/conditional/ssr.ts') }
           }
-          return { id: resolve('fixtures/src/conditional/browser.ts') }
+          return { id: resolve('fixtures/src/conditional/web.ts') }
         },
       },
     ],

test/coverage-test/fixtures/src/conditional/ssr.ts

@@ -0,0 +1,3 @@
+export function ssr() {
+  return "This is for ssr transform"
+}

test/coverage-test/fixtures/src/conditional/web.ts

@@ -0,0 +1,3 @@
+export function web() {
+  return "This is for web transform"
+}

test/coverage-test/test/include-exclude.test.ts

@@ -225,7 +225,7 @@ test('overridden exclude should still apply defaults', async () => {
   expect(coverageMap.files()).toMatchInlineSnapshot(`{}`)
 })
 
-test('uncovered files are transformed correctly', async () => {
+test('uncovered files are transformed correctly (node and browser)', async () => {
   await runVitest({
     config: 'fixtures/configs/vitest.config.conditional.ts',
     include: ['fixtures/test/math.test.ts'],
@@ -242,20 +242,44 @@ test('uncovered files are transformed correctly', async () => {
     expect(files).toMatchInlineSnapshot(`
       [
         "<process-cwd>/fixtures/src/math.ts",
-        "<process-cwd>/fixtures/src/conditional/browser.ts",
+        "<process-cwd>/fixtures/src/conditional/web.ts",
       ]
     `)
   }
   else {
     expect(files).toMatchInlineSnapshot(`
       [
         "<process-cwd>/fixtures/src/math.ts",
-        "<process-cwd>/fixtures/src/conditional/node.ts",
+        "<process-cwd>/fixtures/src/conditional/ssr.ts",
       ]
     `)
   }
 })
 
+test('uncovered files are transformed correctly (jsdom)', async ({ skip }) => {
+  skip(isBrowser(), 'node relevant test')
+
+  await runVitest({
+    config: 'fixtures/configs/vitest.config.conditional.ts',
+    include: ['fixtures/test/math.test.ts'],
+    environment: 'jsdom',
+    coverage: {
+      include: ['fixtures/src/math.ts', 'fixtures/src/conditional/*'],
+      reporter: 'json',
+    },
+  })
+
+  const coverageMap = await readCoverageMap()
+  const files = coverageMap.files()
+
+  expect(files).toMatchInlineSnapshot(`
+      [
+        "<process-cwd>/fixtures/src/math.ts",
+        "<process-cwd>/fixtures/src/conditional/web.ts",
+      ]
+    `)
+})
+
 test('files included and excluded in plugin\'s configureVitest are excluded', async () => {
   await runVitest({
     config: 'fixtures/configs/vitest.config.configure-vitest-hook.ts',