fix(snapshot): treat empty string as valid snapshot by mayrang · Pull Request #10188 · vitest-dev/vitest

mayrang · 2026-04-24T15:19:37Z

Description

Related toMatchAriaInlineSnapshot cannot match empty aria trees #10158

toMatchAriaInlineSnapshot('') treats an empty string as "no snapshot provided"
because '' is falsy in JavaScript. This makes it impossible to assert that an
element has an empty aria tree (e.g. all content is aria-hidden="true").

The fix replaces 5 truthiness checks (if (x), !!x, x ?, x &&) with
explicit !== undefined checks in chai.ts, client.ts, and state.ts.
This aligns the domain snapshot path with the non-domain path, which already
uses expected !== undefined at state.ts:516.

Testing

Verified using the KV domain snapshot fixture (non-aria):

Added empty string handling to KV adapter parseExpected
Added empty snapshot test case with toMatchKvInlineSnapshot(\`)`
Updated integration test assertions to include the new case
All 24 snapshot test files / 45 tests pass

A browser test for the empty aria tree case will be added as a follow-up once
ivya supports empty templates (vitest-dev/ivya#17).

Impact

No breaking changes — only changes how "" (empty string) is distinguished
from undefined (no snapshot)
Non-domain snapshots (toMatchInlineSnapshot, toMatchSnapshot) are
unaffected; they already use the correct !== undefined pattern
Existing aria snapshot tests remain unchanged and pass as before

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

It's really useful if your PR references an issue where it is discussed ahead of time.
Read the Contributing Guidelines.
PR title follows conventional commits format.

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mayrang · 2026-04-24T16:41:00Z

Note: This PR intentionally doesn't include a browser test for the empty aria snapshot case. The test requires parseAriaTemplate('') to return an empty fragment instead of throwing, which is currently an ivya-side limitation.

I've submitted a fix for that at vitest-dev/ivya#17. Once it lands and the dependency is bumped, I'll follow up with a PR adding the test coverage.

hi-ogawa

We have test fixture for non-aria domain snapshot, so we should be able to test the change without waiting for vitest-dev/ivya#17.

Add test coverage using the KV domain snapshot fixture to verify that empty string '' is treated as a valid snapshot, not as "no snapshot". - Add empty string handling to KV adapter parseExpected - Add 'empty snapshot' test case to domain-inline fixture - Update integration test assertions for the new case - Update domain-error snapshot line numbers

mayrang · 2026-04-25T12:15:52Z

Thanks for the suggestion! Added a test using the KV domain snapshot fixture — toMatchKvInlineSnapshot(\`)with an empty object{}. I also added empty string handling to the KV adapter's parseExpectedto return{}` for empty input.

hi-ogawa

Can you do same for test/snapshots/test/fixtures/domain/basic.test.ts?

mayrang · 2026-04-25T12:39:06Z

Done! Added test('empty snapshot', () => { expect({}).toMatchKvSnapshot() }) to the file-based fixture as well.

hi-ogawa

Thanks. I updated kv adapter to actually test empty string, which then revealed pollMatchDomain case wasn't fixed fully, then fixed that. I also added test case for non-domain snapshot and confirmed that's also fixed.

Copilot

Pull request overview

Fixes domain inline snapshot handling so an empty string ("") is treated as a provided snapshot (not “no snapshot provided”), which unblocks assertions like toMatchAriaInlineSnapshot('') for empty aria trees and aligns domain snapshot behavior with existing non-domain snapshot logic.

Changes:

Replaced truthiness checks with explicit !== undefined checks in the domain snapshot flow (chai integration, snapshot client, snapshot state) so "" is considered a valid snapshot.
Added/updated snapshot fixtures and integration tests to cover empty-string snapshots for domain snapshots and custom serializer output.
Updated expected snapshot-file outputs and error snapshots to include the new “empty snapshot” cases.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/snapshots/test/fixtures/domain/basic.ts	KV domain adapter updated to render/parse empty snapshots.
test/snapshots/test/fixtures/domain/basic.test.ts	Adds an “empty snapshot” domain fixture test.
test/snapshots/test/fixtures/domain-inline/basic.test.ts	Adds an inline empty snapshot fixture test.
test/snapshots/test/fixtures/domain-poll/basic.test.ts	Adds a polled empty snapshot fixture test.
test/snapshots/test/fixtures/domain-poll-inline/basic.test.ts	Adds a polled inline empty snapshot fixture test.
test/snapshots/test/fixtures/custom-serializers-empty/vitest.config.ts	New fixture config for empty serializer output coverage.
test/snapshots/test/fixtures/custom-serializers-empty/basic.test.ts	New fixture validating empty/whitespace serializer outputs with file/inline snapshots.
test/snapshots/test/fixtures/custom-serializers-empty/snapshots/basic.test.ts.snap	New fixture snapshot file covering empty/whitespace file snapshots.
test/snapshots/test/domain.test.ts	Updates integration expectations to include the new empty snapshot case.
test/snapshots/test/domain-inline.test.ts	Updates integration expectations to include inline empty snapshot usage.
test/snapshots/test/domain-poll.test.ts	Updates poll integration expectations to include empty snapshot results.
test/snapshots/test/domain-poll-inline.test.ts	Updates poll+inline integration expectations to include empty snapshot usage.
test/snapshots/test/custom-serializers.test.ts	Adds integration test coverage for empty serializer output behavior.
packages/vitest/src/integrations/snapshot/chai.ts	Treats `inlineSnapshot === ""` as provided (strip indentation when not `undefined`).
packages/snapshot/src/client.ts	Uses `expectedSnapshot.data !== undefined` and allows `stableResult.rendered === ""`.
packages/snapshot/src/port/state.ts	Marks `hasSnapshot` true when snapshot data is an empty string (not `undefined`).

mayrang mentioned this pull request Apr 24, 2026

toMatchAriaInlineSnapshot cannot match empty aria trees #10158

Closed

6 tasks

This was referenced Apr 24, 2026

parseAriaTemplate throws on empty string input vitest-dev/ivya#16

Closed

fix: support empty template in parseAriaTemplate vitest-dev/ivya#17

Merged

hi-ogawa requested changes Apr 25, 2026

View reviewed changes

mayrang force-pushed the fix/empty-aria-inline-snapshot branch from da79634 to faaf11e Compare April 25, 2026 12:12

hi-ogawa reviewed Apr 25, 2026

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test: add empty snapshot test to file-based domain fixture

f47ac75

hi-ogawa self-assigned this Apr 26, 2026

Merge branch 'main' into fix/empty-aria-inline-snapshot

1680774

hi-ogawa mentioned this pull request Apr 27, 2026

test: fix kv domain snapshot example #10207

Merged

7 tasks

test: test empty non-domain snapshot

9f6cc18

hi-ogawa changed the title ~~fix(snapshot): treat empty string as valid domain snapshot~~ fix(snapshot): treat empty string as valid snapshot Apr 27, 2026

fix: fix pollMatchDomain + actually test empty render

babb3c8

hi-ogawa previously approved these changes Apr 27, 2026

View reviewed changes

hi-ogawa requested a review from Copilot April 27, 2026 07:30

Copilot started reviewing on behalf of hi-ogawa April 27, 2026 07:30 View session

Copilot AI reviewed Apr 27, 2026

View reviewed changes

Comment thread test/snapshots/test/fixtures/domain/basic.ts

hi-ogawa added 3 commits April 27, 2026 17:34

Merge branch 'main' into fix/empty-aria-inline-snapshot

372bd2b

chore: remove test snapshot

e672413

gitignore

79bf076

hi-ogawa dismissed their stale review via 79bf076 April 27, 2026 08:34

hi-ogawa approved these changes Apr 27, 2026

View reviewed changes

hi-ogawa merged commit e145d57 into vitest-dev:main Apr 27, 2026
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fix(snapshot): treat empty string as valid snapshot#10188

fix(snapshot): treat empty string as valid snapshot#10188
hi-ogawa merged 8 commits intovitest-dev:mainfrom
mayrang:fix/empty-aria-inline-snapshot

mayrang commented Apr 24, 2026 •

edited by hi-ogawa

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Description

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mayrang commented Apr 24, 2026 •

edited by hi-ogawa

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