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Evidenceqs-37

parser discards first empty value in array

qs#37, at commit 8a90b77. A closed issue from a repository Credda did not choose.

LIVE2026-09-20

RIGHT_FAILURE

executed against the upstream checkout.

Outcome
REPRODUCED_NOT_DIAGNOSED
Wall time
59.0s
Checks
5 passed of 5 applicable

RECORDED

NOT_GRADED

graded from the transcript committed with this case.

Outcome
not recorded
Checks
none run
Repository
ljharb/qs
Issue
#37
Pinned commit
8a90b77150d3b04f1b4027f8c1297fa8eb68692e

01The signal

The report, exactly as it was filed.

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

qs#37 · as filedcommit 8a90b77

parser discards first empty value in array

Hi, I use this awesome library. But there is one wonder point.

```
var qs = require("qs");
console.dir(qs.parse("x[]=")); // case1
console.dir(qs.parse("a[]=&a[]=b&a[]=c")); // case2
console.dir(qs.parse("a[]=b&a[]=&a[]=c")); // case3
console.dir(qs.parse("a[]=b&a[]=c&a[]=")); // case4
```

```
{ x: [ '' ] }
{ a: [ 'b', 'c' ] }
{ a: [ 'b', '', 'c' ] }
{ a: [ 'b', 'c', '' ] }
```

Is case2 expected value?
Repository
ljharb/qs
Issue
#37
Commit
8a90b77150d3b04f1b4027f8c1297fa8eb68692e
Why this commit
The first parent of the fix commit 9c339b3bc829fbb11a20f9c92d556aa2ef5adfd8, which GitHub binds to this issue via CLOSED_EVENT_COMMIT. 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
qs.parse("a[]=&a[]=b&a[]=c") produces { a: [ 'b', 'c' ] }; the fix makes it produce { a: [ '', 'b', 'c' ] }.
Expression
qs.parse("a[]=&a[]=b&a[]=c")
Reported output
{ a: [ 'b', 'c' ] }
Where that came from
Proposed by a model reading this report and nothing else -- it never saw the repository or the fix commit -- and read back as a claim by the same parser the harvest uses, SAME_LINE form: `qs.parse("a[]=&a[]=b&a[]=c") //=> { a: [ 'b', 'c' ] }`. The report sat in the ANNOTATION_IS_PROSE bucket, which no regex reaches. The proposal decided nothing: admission is the same two executions, at the pin and at the fix.

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
`qs.parse("a[]=&a[]=b&a[]=c")` still produces { a: [ 'b', 'c' ] } (read { a: [ 'b', 'c' ] })
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`qs.parse("a[]=&a[]=b&a[]=c")` still produces { a: [ 'b', 'c' ] } (read { a: [ 'b', 'c' ] })
right-failurepassReproduced the reported failure: qs.parse("a[]=&a[]=b&a[]=c") produces { a: [ 'b', 'c' ] }; the fix makes it produce { a: [ '', 'b', 'c' ] }.
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 8a90b77, 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/ljharb/qs
git checkout 8a90b77150d3b04f1b4027f8c1297fa8eb68692e
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