Description

• Closes Support merging reports for non-sharded multi-environment runs #9954
• Closes feat: support merge reports for non-sharded multi-environment runs #9967 (supersedes)

Alternative take for #9967 (comment)

This PR adds new blob reporter option label so --merge-reports can distinguish results from the same test files across different environments, such as linux/macos/windows CI jobs.

Usage example

Set VITEST_BLOB_LABEL when creating blobs:

VITEST_BLOB_LABEL=linux vitest run --reporter=blob
VITEST_BLOB_LABEL=macos vitest run --reporter=blob

Or pass the label via the blob reporter option:

// vitest.config.ts
export default defineConfig({
  test: {
    reporters: [
      ['blob', { label: process.platform }],
    ],
  },
})

The label is included in the default blob filename (blob-linux.json) to avoid collisions. When merging, each labeled run is shown separately:

$ vitest --merge-reports
 ✓  linux  src/basic.test.ts (2 tests)
 ✓  macos  src/basic.test.ts (2 tests)

How it works

The label is a blob reporter option, with VITEST_BLOB_LABEL as an environment-variable shortcut for CI usage. During config resolution, Vitest extracts the label from ['blob', { label }] or process.env.VITEST_BLOB_LABEL and stores it as internal core config (mergeReportsLabel).

During the original test run, this label is not exposed as a normal built-in reporter label. This keeps terminal output unchanged for runs that create blobs with another reporter enabled, for example reporters: ['default', ['blob', { label: 'linux' }]].

The label is stored in blob task metadata and salts the file identity used for merged reports, so state deduplication can keep same-filepath files from different environments separate. The default blob output filename also uses the label as blob-(label)-(shard).json when no explicit output file is configured.

Reporters read the label from merged blob metadata and display it when replaying --merge-reports.

The difference from #9967

Demo

I setup CI to upload html reports for test/cli and test/core. It's viewable on newly introduced viewer #10023.

https://viewer.vitest.dev/?url=https://github.com/vitest-dev/vitest/actions/runs/24275938517/artifacts/6383832383

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Tests

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