feat: support merge reports for non-sharded multi-environment runs

.github/workflows/ci.yml

@@ -116,6 +116,8 @@ jobs:
 
       - name: Test
         run: pnpm run test:ci
+        env:
+          VITEST_BLOB_LABEL_DOGFOOD: ${{ matrix.os }}-node-${{ matrix.node_version }}
 
       - name: Test Examples
         run: pnpm run test:examples
@@ -127,6 +129,17 @@ jobs:
           path: test/ui/test-results/
           retention-days: 30
 
+      - uses: actions/upload-artifact@v7
+        if: ${{ !cancelled() }}
+        with:
+          name: vitest-blob-${{ matrix.os }}-node-${{ matrix.node_version }}
+          path: |
+            README.md
+            test/core/.vitest-reports
+            test/cli/.vitest-reports
+          retention-days: 1
+          include-hidden-files: true
+
   test-cached:
     needs: changed
     name: 'Cache&Test: node-${{ matrix.node_version }}, ${{ matrix.os }}'
@@ -248,3 +261,39 @@ jobs:
           name: playwright-report-rolldown
           path: rolldown/test/ui/test-results/
           retention-days: 30
+
+  merge-reports:
+    needs: test
+    if: ${{ !cancelled() }}
+    runs-on: ubuntu-latest
+    name: Merge Reports
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: ./.github/actions/setup-and-cache
+
+      - name: Install
+        run: pnpm i
+
+      - name: Build
+        run: pnpm run build
+
+      - uses: actions/download-artifact@v4
+        with:
+          pattern: vitest-blob-*
+          merge-multiple: true
+
+      - name: Merge reports
+        continue-on-error: true
+        run: pnpm --filter=./test/core --filter=./test/cli --no-bail --sequential test --merge-reports --reporter=html
+
+      - uses: actions/upload-artifact@v7
+        if: ${{ !cancelled() }}
+        with:
+          name: vitest-merge-reports
+          path: |
+            README.md
+            test/core/html
+            test/cli/html
+          retention-days: 7

docs/guide/cli.md

@@ -225,7 +225,7 @@ You cannot use this option with `--watch` enabled (enabled in dev by default).
 :::
 
 ::: tip
-If `--reporter=blob` is used without an output file, the default path will include the current shard config to avoid collisions with other Vitest processes.
+If `--reporter=blob` is used without an output file, the default path will include the current shard config and [label](/guide/reporters#labels) to avoid collisions with other Vitest processes.
 :::
 
 ### merge-reports

docs/guide/improving-performance.md

@@ -144,9 +144,10 @@ on:
       - main
 jobs:
   tests:
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
+        os: [ubuntu-latest, macos-latest]
         shardIndex: [1, 2, 3, 4]
         shardTotal: [4]
     steps:
@@ -163,12 +164,14 @@ jobs:
 
       - name: Run tests
         run: pnpm run test --reporter=blob --shard=${{ matrix.shardIndex }}/${{ matrix.shardTotal }}
+        env:
+          VITEST_BLOB_LABEL: ${{ matrix.os }}
 
       - name: Upload blob report to GitHub Actions Artifacts
         if: ${{ !cancelled() }}
         uses: actions/upload-artifact@v4
         with:
-          name: blob-report-${{ matrix.shardIndex }}
+          name: blob-report-${{ matrix.os }}-${{ matrix.shardIndex }}
           path: .vitest-reports/*
           include-hidden-files: true
           retention-days: 1
@@ -177,7 +180,7 @@ jobs:
         if: ${{ !cancelled() }}
         uses: actions/upload-artifact@v4
         with:
-          name: blob-attachments-${{ matrix.shardIndex }}
+          name: blob-attachments-${{ matrix.os }}-${{ matrix.shardIndex }}
           path: .vitest-attachments/**
           include-hidden-files: true
           retention-days: 1

docs/guide/reporters.md

@@ -670,13 +670,18 @@ By default, stores all results in `.vitest-reports` folder, but can be overridde
 npx vitest --reporter=blob --outputFile=reports/blob-1.json
 ```
 
-We recommend using this reporter if you are running Vitest on different machines with the [`--shard`](/guide/cli#shard) flag.
-All blob reports can be merged into any report by using `--merge-reports` command at the end of your CI pipeline:
+We recommend using this reporter if you are running Vitest on different machines with the [`--shard`](/guide/cli#shard) flag or across multiple environments (e.g., linux/macos/windows). All blob reports can be merged into any report by using `--merge-reports` command at the end of your CI pipeline:
 
 ```bash
 npx vitest --merge-reports=reports --reporter=json --reporter=default
 ```
 
+When running the same tests across multiple environments, set the `label` option (or `VITEST_BLOB_LABEL` environment variable) to distinguish each environment's blob. Vitest reads labels at merge time and creates separate project entries automatically (e.g., `myproject [linux]`, `myproject [macos]`).
+
+```bash
+VITEST_BLOB_LABEL=linux vitest run --reporter=blob
+```
+
 Blob reporter output doesn't include file-based [attachments](/api/advanced/artifacts.html#testattachment).
 Make sure to merge [`attachmentsDir`](/config/attachmentsdir) separately alongside blob reports on CI when using this feature.
 

packages/vitest/src/node/core.ts

@@ -605,7 +605,7 @@ export class Vitest {
         throw new Error('Cannot merge reports when `--reporter=blob` is used. Remove blob reporter from the config first.')
       }
 
-      const { files, errors, coverages, executionTimes } = await readBlobs(this.version, directory || this.config.mergeReports, this.projects)
+      const { files, errors, coverages, executionTimes } = await readBlobs(this, directory || this.config.mergeReports)
       this.state.blobs = { files, errors, coverages, executionTimes }
 
       await this.report('onInit', this)

packages/vitest/src/node/project.ts

@@ -727,7 +727,7 @@ export class TestProject {
   }
 
   /** @internal */
-  static _cloneBrowserProject(parent: TestProject, config: ResolvedConfig): TestProject {
+  static _cloneProject(parent: TestProject, config: ResolvedConfig): TestProject {
     const clone = new TestProject(parent.vitest, undefined, parent.tmpDir)
     clone.runner = parent.runner
     clone._vite = parent._vite

packages/vitest/src/node/projects/resolveProjects.ts

@@ -259,7 +259,7 @@ export async function resolveBrowserProjects(
       names.add(name)
       const clonedConfig = cloneConfig(project, config)
       clonedConfig.name = name
-      const clone = TestProject._cloneBrowserProject(project, clonedConfig)
+      const clone = TestProject._cloneProject(project, clonedConfig)
       resolvedProjects.push(clone)
     })
 

packages/vitest/src/node/reporters/blob.ts

@@ -7,12 +7,19 @@ import type { Reporter } from '../types/reporter'
 import type { TestModule } from './reported-tasks'
 import { existsSync } from 'node:fs'
 import { mkdir, readdir, readFile, stat, writeFile } from 'node:fs/promises'
+import { calculateSuiteHash, generateFileHash } from '@vitest/runner/utils'
+import { deepClone } from '@vitest/utils/helpers'
 import { parse, stringify } from 'flatted'
 import { dirname, resolve } from 'pathe'
 import { getOutputFile } from '../../utils/config-helpers'
 
 export interface BlobOptions {
   outputFile?: string
+  /**
+   * Label for this environment's blob report (e.g., "linux", "node-22").
+   * Can also be set via `VITEST_BLOB_LABEL` environment variable.
+   */
+  label?: string
 }
 
 export class BlobReporter implements Reporter {
@@ -46,13 +53,14 @@ export class BlobReporter implements Reporter {
     const errors = [...unhandledErrors]
     const coverage = this.coverage
 
+    const label = this.options.label ?? process.env.VITEST_BLOB_LABEL
+
     let outputFile
       = this.options.outputFile ?? getOutputFile(this.ctx.config, 'blob')
     if (!outputFile) {
       const shard = this.ctx.config.shard
-      outputFile = shard
-        ? `.vitest-reports/blob-${shard.index}-${shard.count}.json`
-        : '.vitest-reports/blob.json'
+      const suffix = [label, shard && `${shard.index}-${shard.count}`].filter(Boolean).join('-')
+      outputFile = suffix ? `.vitest-reports/blob-${suffix}.json` : '.vitest-reports/blob.json'
     }
 
     const environmentModules: MergeReportEnvironmentModules = {}
@@ -89,6 +97,7 @@ export class BlobReporter implements Reporter {
       coverage,
       executionTime,
       environmentModules,
+      label,
     ] satisfies MergeReport
 
     const reportFile = resolve(this.ctx.config.root, outputFile)
@@ -110,9 +119,8 @@ export async function writeBlob(content: MergeReport, filename: string): Promise
 }
 
 export async function readBlobs(
-  currentVersion: string,
+  ctx: Vitest,
   blobsDirectory: string,
-  projectsArray: TestProject[],
 ): Promise<MergedBlobs> {
   // using process.cwd() because --merge-reports can only be used in CLI
   const resolvedDir = resolve(process.cwd(), blobsDirectory)
@@ -126,15 +134,15 @@ export async function readBlobs(
       )
     }
     const content = await readFile(fullPath, 'utf-8')
-    const [version, files, errors, coverage, executionTime, environmentModules] = parse(
+    const [version, files, errors, coverage, executionTime, environmentModules, label] = parse(
       content,
     ) as MergeReport
     if (!version) {
       throw new TypeError(
         `vitest.mergeReports() expects all paths in "${blobsDirectory}" to be files generated by the blob reporter, but "${filename}" is not a valid blob file`,
       )
     }
-    return { version, files, errors, coverage, file: filename, executionTime, environmentModules }
+    return { version, label, files, errors, coverage, file: filename, executionTime, environmentModules }
   })
   const blobs = await Promise.all(promises)
 
@@ -151,13 +159,41 @@ export async function readBlobs(
     )
   }
 
-  if (!versions.has(currentVersion)) {
+  if (!versions.has(ctx.version)) {
     throw new Error(
-      `the blobs in "${blobsDirectory}" were generated by a different version of Vitest. Expected v${currentVersion}, but received v${blobs[0].version}`,
+      `the blobs in "${blobsDirectory}" were generated by a different version of Vitest. Expected v${ctx.version}, but received v${blobs[0].version}`,
+    )
+  }
+
+  // Auto-discover labels and duplicate projects if needed
+  const labels = discoverMergeReportLabels(blobs)
+  if (labels) {
+    ctx.projects = resolveMergeReportProjects(
+      ctx.projects,
+      labels,
     )
   }
 
+  // Rewrite blob data so they get attached to duplicated projects based on labels
+  for (const blob of blobs) {
+    const label = blob.label
+    if (!label) {
+      continue
+    }
+    for (const file of blob.files) {
+      file.projectName = suffixProjectName(file.projectName, label)
+      file.id = generateFileHash(file.name, file.projectName)
+      calculateSuiteHash(file)
+    }
+    const rewritten: MergeReportEnvironmentModules = {}
+    for (const [projectName, modules] of Object.entries(blob.environmentModules)) {
+      rewritten[suffixProjectName(projectName, label)] = modules
+    }
+    blob.environmentModules = rewritten
+  }
+
   // Restore module graph
+  const projectsArray = ctx.projects
   const projects = Object.fromEntries(
     projectsArray.map(p => [p.name, p]),
   )
@@ -211,6 +247,58 @@ export async function readBlobs(
   }
 }
 
+function suffixProjectName(originalName: string | undefined, label: string): string {
+  return originalName ? `${originalName} [${label}]` : label
+}
+
+function resolveMergeReportProjects(
+  projects: TestProject[],
+  labels: string[],
+): TestProject[] {
+  const names = new Set(projects.map(p => p.name))
+  const clonedProjects: TestProject[] = []
+
+  for (const project of projects) {
+    for (const label of labels) {
+      const name = suffixProjectName(project.name || undefined, label)
+
+      if (names.has(name)) {
+        throw new Error(
+          `Project name "${name}" is not unique. All projects should have unique names. Make sure your configuration is correct.`,
+        )
+      }
+
+      names.add(name)
+      const config = deepClone(project.config)
+      config.name = name
+      // TODO: importing `import "../project"` breaks some tests
+      clonedProjects.push((project.constructor as typeof TestProject)._cloneProject(project, config))
+    }
+  }
+
+  return clonedProjects
+}
+
+function discoverMergeReportLabels(blobs: { file: string; label?: string }[]): string[] | undefined {
+  const labeled = blobs.filter(b => b.label)
+
+  if (!labeled.length) {
+    return undefined
+  }
+
+  // TODO: support mix of labeled and unlabeled blobs?
+  const unlabeled = blobs.filter(b => !b.label)
+  if (unlabeled.length) {
+    throw new Error(
+      `vitest.mergeReports() requires all blob files to have a label when any blob has one. `
+      + `Missing label in: ${unlabeled.map(b => `"${b.file}"`).join(', ')}`,
+    )
+  }
+
+  const labels = new Set(labeled.map(b => b.label!))
+  return [...labels]
+}
+
 export interface MergedBlobs {
   files: File[]
   errors: unknown[]
@@ -225,6 +313,7 @@ type MergeReport = [
   coverage: unknown,
   executionTime: number,
   environmentModules: MergeReportEnvironmentModules,
+  label?: string,
 ]
 
 interface MergeReportEnvironmentModules {