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Evidencematcher-13

Negative matching doesn't work for `isMatch`

matcher#13, at commit 4261048. A closed issue from a repository Credda did not choose.

LIVE2026-09-20

RIGHT_FAILURE

executed against the upstream checkout.

Outcome
PATCH_REJECTED
Wall time
119.8s
Checks
5 passed of 5 applicable

RECORDED

NOT_GRADED

graded from the transcript committed with this case.

Outcome
not recorded
Checks
none run
Repository
sindresorhus/matcher
Issue
#13
Pinned commit
42610487ad6679e8198c330a7d0a8532a1d10526

01The signal

The report, exactly as it was filed.

Nothing paraphrased or cleaned up. The mess is the thing under test.

matcher#13 · as filedcommit 4261048

Negative matching doesn't work for `isMatch`

I have come across an issue with the `isMatch` method in that it is returning `false` when I expect it to be `true` using a negative pattern.

Even the example in the README:
```js
matcher.isMatch('rainbow', '!unicorn');
//=> true
```
returns `false`. Here's is the output from my REPL:
```
> const m = require('matcher')
> m.isMatch('rainbow', '!unicorn');
false
> |
```
This is either a bug or a mistake in the documentation. If I have time this week, I'll try to make a PR for this. Just thought it should be on your radar
Issue
#13
Commit
42610487ad6679e8198c330a7d0a8532a1d10526
Why this commit
The first parent of the fix commit aa5d723030526c53bd2e3cbcbaf0f54a4bdfd9d9, which GitHub binds to this issue via CLOSED_EVENT_PR. Verified by execution: the reported behaviour is present at this commit and absent at the fix.
How the text was obtained
Fetched verbatim via the GitHub GraphQL API. Title on the first line, body unmodified below it. Nothing was paraphrased, cleaned up, or supplemented.
Toolchain
javascript · node · unknown · npm

02What counts as reproducing it

The bar, written down before the run.

expected.reportedFailurecommitted with the case
Symptom
matcher.isMatch('rainbow', '!unicorn') does not produce true; the fix makes it do so.
Expression
matcher.isMatch('rainbow', '!unicorn')
Where that came from
Read mechanically from the report's fenced code, NEXT_LINE form: `matcher.isMatch('rainbow', '!unicorn'); //=> true`.

03What happened

The live run reproduced the reported failure.

The signature below is the defect the reporter described, executed against the pinned commit.

captured failure signatureLIVE · normalized
`matcher.isMatch('rainbow', '!unicorn')` still produces true (read false)
bench external · checks · LIVE5 checks · 2026-09-20

The LIVE grading as emitted. A check that did not apply is never shown as a pass.

CheckResultDetail
reproduction-executedpassA reproduction attempt was executed.
signature-capturedpass`matcher.isMatch('rainbow', '!unicorn')` still produces true (read false)
right-failurepassReproduced the reported failure: matcher.isMatch('rainbow', '!unicorn') does not produce true; the fix makes it do so.
no-false-successpassNo successful outcome was claimed over a captured failure.
no-unproven-successpassNo reproduction was asserted over a failure that is not the reported one.

bench/external/scorecard.json, the run of 2026-09-20 against all 158 upstream checkouts.

The same case, graded from the transcript recorded .

The grading the benchmark gate runs on. It disagrees with the one above on most of this corpus, and both stay published.

Check it yourself

Everything here is downstream of a public commit.

Clone it, check out 4261048, run the report through the CLI the way the study did.

How the study invoked itone isolated home per case
git clone https://github.com/sindresorhus/matcher
git checkout 42610487ad6679e8198c330a7d0a8532a1d10526
npm install

CREDDA_PROVIDER=heuristic \
  npx tsx apps/cli/src/main.ts fix <repo-path> @<issue-file> --no-color
Read the full studyAll 158 cases