Evidencedeepmerge-150

Symbol properties are ignored

deepmerge#150, at commit 6c88021. 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: 71.3s
Checks: 5 passed of 5 applicable

RECORDED

WRONG_FAILURE

graded from the transcript committed with this case.

Outcome: INCONCLUSIVE
Wall time: 2.8s
Checks: 4 passed of 5 applicable

Repository: TehShrike/deepmerge
Issue: #150
Pinned commit: 6c88021a3907592ae8636832cebda4d2de358700

01The signal

The report, exactly as it was filed.

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

deepmerge#150 · as filedcommit 6c88021

Symbol properties are ignored

Symbols can be used as property keys, but they are ignored.

```javascript
const merge = require('deepmerge');

const mySymbol = Symbol('mySymbol');

const x = { value: 42, [mySymbol]: 'hello' };

console.log(x);
// { value: 42, [Symbol(mySymbol)]: 'hello' }

const y = { other: 33 };
const z = merge(x, y);

console.log(z);
// { value: 42, other: 33 }
// expected: { value: 42, [Symbol(mySymbol)]: 'hello', other: 33 }
```

Repository: TehShrike/deepmerge
Issue: #150
Commit: 6c88021a3907592ae8636832cebda4d2de358700
Why this commit: The fix commit's parent where the closing commit was identifiable in the repository, otherwise the commit that was HEAD of the default branch at the moment the issue was filed. fixCommit bound 2026-08-26: issue #150 was closed 17 minutes after PR #151 ('Support symbol keys') merged. The MERGE commit f5f67eb is deliberately NOT what is bound: `git show --name-only` on a merge prints a combined diff, which for f5f67eb is empty, and localization-report.ts reads that as no ground truth at all. 8d53ab9 is the source half of that PR -- it replaces both `Object.keys(...)` walks in mergeObject with a getKeys() that concatenates Object.getOwnPropertySymbols, which is precisely the reporter's dropped `[mySymbol]: 'hello'` -- and it touches index.js alone. Its branch root 746ef03 ('failing test for symbol keys') has the pinned commit as its parent.
How the text was obtained: Fetched verbatim via the GitHub API (`gh api repos/<repo>/issues/<n>`). Title on the first line, body unmodified below it. Nothing was paraphrased, cleaned up, or supplemented.
Toolchain: javascript · node · tape · npm

02What counts as reproducing it

The bar, written down before the run.

expected.reportedFailurecommitted with the case

Symptom: Symbol-keyed properties are dropped by merge().
Expression: z
Reported output: { value: 42, other: 33 }
Where that came from: The snippet binds `const z = merge(x, y)` and the comment under `console.log(z);` quotes what it printed. The line below it starts "expected:" and is the reporter's wish, not their observation.

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

`z` still produces { value: 42, other: 33 } (read { value: 42, other: 33 })

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.

Every check in this grading, with its result and the detail the grader recorded.
Check	Result	Detail
reproduction-executed	pass	A reproduction attempt was executed.
signature-captured	pass	`z` still produces { value: 42, other: 33 } (read { value: 42, other: 33 })
right-failure	pass	Reproduced the reported failure: Symbol-keyed properties are dropped by merge().
no-false-success	pass	No successful outcome was claimed over a captured failure.
no-unproven-success	pass	No 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.

bench external · checks · RECORDED5 checks

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

Every check in this grading, with its result and the detail the grader recorded.
Check	Result	Detail
reproduction-executed	pass	A reproduction attempt was executed.
signature-captured	pass	Error: Cannot find module 'deepmerge'
right-failure	fail	Expected `z` still producing { value: 42, other: 33 }.
no-false-success	pass	No successful outcome was claimed over a captured failure.
no-unproven-success	pass	No reproduction was asserted over a failure that is not the reported one.

captured failure signatureRECORDED · normalized

Error: Cannot find module 'deepmerge'

Cannot find module 'deepmerge' — the reporter's snippet requires the package by its published name, which does not resolve inside the repository checkout. Outcome was not stable across repeated runs of identical input: 4 of 5 runs gave INCONCLUSIVE, 1 gave NO_CHANGE_REQUIRED. See the determinism note in the README.

Provider heuristic, sandbox local. bench/external/README.md, the Results table and "The top three failure modes". Run 2026-08-21. Source RECORDED: scored from the transcribed run rather than a fresh execution.

Check it yourself

Everything here is downstream of a public commit.

Clone it, check out 6c88021, 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/TehShrike/deepmerge
git checkout 6c88021a3907592ae8636832cebda4d2de358700
npm install

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

Read the full study All 158 cases