[eslint-miner] feat(eslint): add no-caught-error-interpolation rule#48175
[eslint-miner] feat(eslint): add no-caught-error-interpolation rule#48175github-actions[bot] wants to merge 5 commits into
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Adds a new custom ESLint rule that detects bare caught-error variable
interpolation in template literals (e.g. `...${err}...`).
Problem: Directly interpolating a caught error variable in a template
literal is unreliable:
- For Error objects: produces redundant 'Error: message' prefix
- For non-Error throws: produces useless '[object Object]'
The rule flags bare Identifier expressions in template literals when the
variable is a caught error param (try/catch, .catch(), or .then rejection
handler). It suggests using getErrorMessage(err) if available or String(err)
as an import-free alternative.
Real instances found and flagged:
- actions/setup/js/copilot_sdk_driver.cjs:87
- actions/setup/js/copilot_harness.cjs:850
Not flagged (intentionally excluded):
- err.message, err.stack, err.toString() — covered by no-unsafe-catch-error-property
- String(err), getErrorMessage(err) — already correct forms
- Outer catch vars inside non-rejection function callbacks (false-positive guard)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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✅ Design Decision Gate 🏗️ completed the design decision gate check. No ADR enforcement needed: PR #48175 does not have the 'implementation' label and has 0 new lines of code in business logic directories (threshold: 100). |
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✅ PR Code Quality Reviewer completed the code quality review. |
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✅ Test Quality Sentinel completed test quality analysis. |
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🧠 Matt Pocock Skills Reviewer has completed the skills-based review. ✅ |
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Pull request overview
Adds an ESLint rule to detect direct interpolation of caught errors in template literals.
Changes:
- Implements and registers
no-caught-error-interpolation. - Adds rule tests and enables it as a warning.
- Provides formatting replacement suggestions.
Show a summary per file
| File | Description |
|---|---|
eslint-factory/src/rules/no-caught-error-interpolation.ts |
Implements detection and suggestions. |
eslint-factory/src/rules/no-caught-error-interpolation.test.ts |
Tests supported patterns. |
eslint-factory/src/index.ts |
Registers the rule. |
eslint-factory/eslint.config.cjs |
Enables the rule. |
Review details
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Comments suppressed due to low confidence (2)
eslint-factory/src/rules/no-caught-error-interpolation.ts:164
String(errorVar)does not remediate the reported behavior: template-literal interpolation already performs string coercion, so both forms produce"Error: message"forErrorand"[object Object]"for a plain object. Applying this suggestion therefore silences the rule without improving the output. OffergetErrorMessageonly (or another formatter that actually handles unknown thrown values), and update the fallback message/tests accordingly.
: ({
messageId: "useStringFallback" as const,
data: { errorVar },
fix(fixer) {
return fixer.replaceText(expr, `String(${errorVar})`);
},
} as const),
eslint-factory/src/rules/no-caught-error-interpolation.ts:140
- Matching only the identifier name reports shadowing locals as caught errors. For example,
catch (err) { { const err = "formatted"; log(${err}); } }is flagged even though the interpolated identifier resolves to the inner string. Verify that the expression's resolved variable is the tracked catch/rejection parameter rather than comparing names.
for (const expr of node.expressions) {
if (!isBareIdentifierExpression(expr)) continue;
if (!caughtNames.has(expr.name)) continue;
- Files reviewed: 4/4 changed files
- Comments generated: 3
- Review effort level: Medium
🧪 Test Quality Sentinel Report
📊 Metrics (19 test cases)
✅ Test StrengthsComprehensive Coverage: 11 valid test cases establish what should NOT be flagged (non-caught vars, alternative accessors, scope boundaries). 8 invalid cases verify rule detection and enforce suggestion/fixer output correctness. Edge Cases: Tests cover try/catch binding, .catch() rejection handlers, .then() rejection handlers, nested non-rejection callbacks, template literals with multiple interpolations, and both CommonJS and ES module contexts. Assertion Quality: All invalid cases verify both (1) error messageId and (2) suggestion/fixer output, enforcing end-to-end fix correctness. No mocking of internal rule logic. Test Inflation: 241 test lines / 171 production lines = 1.41:1 ratio. Acceptable for ESLint rule testing, where comprehensive valid/invalid coverage is standard practice.
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Review: no-caught-error-interpolation ESLint rule
Overall the rule is well-designed and the test coverage is solid. One correctness gap needs fixing before merge.
Blocking issue: FunctionDeclaration nodes are not handled as sentinels in the scope stack (see inline comment on line 101). Named functions declared inside a catch block will cause false positives because the outer catch variable stays visible across the sentinel boundary that should have been inserted.
Non-blocking observations:
- The single-suggestion design (only
getErrorMessageORString, not both) is clean and intentional. isDefinitionAvailableAtNodecorrectly handles hoistedFunctionNamebindings.- Test coverage is thorough for the handled cases.
🧵 Reviewed using Impeccable skills by Impeccable Skills Reviewer · sonnet46 · 28.5 AIC · ⌖ 4.63 AIC · ⊞ 5K
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Request changes — rule logic has medium correctness issues and misleading documentation that should be fixed before merge.
### Findings summary
Medium — false negatives (silent misses)
The sentinel heuristic blocks reporting for any non-rejection callback (forEach, map, setTimeout, etc.) nested inside a catch block. Caught errors interpolated in these callbacks produce no warning. This is a significant coverage gap for a rule whose purpose is reliable detection. If intentional, it must be documented explicitly in docs.description.
Medium — false positives on non-Promise callees
isInlineRejectionHandler fires on any .catch(fn) or .then(_, fn) method call regardless of the receiver type, which will produce false positives with RxJS, Chai, or any custom object with those method names. Needs documentation or a narrower check.
Low — wrong JSDoc on isBareIdentifierExpression
The function comment describes a TemplateLiteral-in-TemplateLiteral check; the implementation checks Identifier. Pure documentation bug but confusing for maintainers.
Low — misleading test comment
Test says outer err is "not accessible" inside setTimeout; it is accessible via closure. The sentinel suppresses the report as a deliberate heuristic, not a scoping rule. Wrong mental model baked into test comments.
🔎 Code quality review by PR Code Quality Reviewer · sonnet46 · 49.3 AIC · ⌖ 5.14 AIC · ⊞ 5.7K
Comment /review to run again
Comments that could not be inline-anchored
eslint-factory/src/rules/no-caught-error-interpolation.ts:319
Wrong JSDoc: the isBareIdentifierExpression comment says "Returns true when node is a TemplateLiteral expression inside a TemplateLiteral expression" — that is completely wrong and describes a different function. The implementation just checks node.type === AST_NODE_TYPES.Identifier.
<details>
<summary>💡 Fix</summary>
Replace the JSDoc with an accurate description:
/**
* Returns true when `expr` is a bare `Identifier` node — i.e. the template
* expression is …
</details>
<details><summary>eslint-factory/src/rules/no-caught-error-interpolation.ts:371</summary>
**Silent false negatives for any non-rejection callback**: caught error variables interpolated inside `arr.map()`, `forEach()`, `setTimeout()`, or any callback that isn't `.catch(fn)` / `.then(_, fn)` are silently skipped — no lint warning is emitted.
<details>
<summary>💡 Details</summary>
When `enterFunction` encounters a function that is NOT an inline rejection handler, it pushes a sentinel that stops `getCaughtVarNames()` from looking further up the stack. This means:
```js
try {
f();
…
</details>
<details><summary>eslint-factory/src/rules/no-caught-error-interpolation.ts:301</summary>
**False positives on non-Promise `.catch()`/`.then()` calls**: `isInlineRejectionHandler` treats any method named `catch` or `then` as a Promise rejection handler, regardless of the receiver type.
<details>
<summary>💡 Details</summary>
Examples that will be incorrectly flagged:
```js
// RxJS observable
observable.catch(err => log(`rx error: ${err}`));
// Chai assertion chain (.then is defined on thenables in test frameworks)
expect(val).to.not.throw().then(err => ...);
// Any custom objec…
</details>
<details><summary>eslint-factory/src/rules/no-caught-error-interpolation.test.ts:109</summary>
**Misleading test comment**: the comment says `err` is "not accessible" inside the `setTimeout` callback, but that is factually wrong — JavaScript closures DO capture the outer `catch (err)` binding. The rule suppresses the report via the sentinel heuristic, not because of scoping rules.
<details>
<summary>💡 Fix</summary>
Update the comment to reflect reality:
```typescript
// The setTimeout callback is treated as a sentinel (non-rejection function),
// so the rule intentionally does NOT re…
</details>
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Skills-Based Review 🧠
Applied /tdd — no blocking issues, but 5 test-coverage gaps worth closing.
📋 Key Themes & Highlights
Key Themes
- Misleading JSDoc:
isBareIdentifierExpressionhas a comment describing aTemplateLiteralcontext that doesn't match its actual behaviour (checks forIdentifier). - Missing edge-case tests: 4 code paths are untested — zero-param
.catch()handler, destructuredcatchparam, ESMimportofgetErrorMessage, and therangeguard inisDefinitionAvailableAtNode. - Defensive guard missing:
isDefinitionAvailableAtNodeindexesrange[0]without checkingrangeis defined — low-probability but worth a one-line guard.
Positive Highlights
- ✅ Well-scoped sentinel mechanism cleanly avoids false positives for outer catch vars in non-rejection callbacks
- ✅ Context-aware suggestion (prefers
getErrorMessageoverString) is a nice ergonomic touch - ✅ Solid coverage of the happy-path cases across both CJS and ESM contexts
- ✅ PR description is clear: problem, rule behavior, real instances, and exclusions all documented
🧠 Reviewed using Matt Pocock's skills by Matt Pocock Skills Reviewer · sonnet46 · 49 AIC · ⌖ 5.15 AIC · ⊞ 6.7K
Comment /matt to run again
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@copilot please run the Unresolved review feedback (newest first):
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… rule - Replace stack-based scope tracking with ESLint scope analysis so closures retain access to outer catch bindings (fixes false negatives from non-rejection function sentinels) - Skip TaggedTemplateExpression nodes — tag functions receive raw values, not string-coerced output - Fix isBareIdentifierExpression JSDoc to accurately describe the function - Add isCaughtErrorVariableDef helper that correctly identifies catch clause bindings (simple identifier only, not destructured params) and inline rejection handler params via scope analysis - Guard definitionNode.range being undefined in isDefinitionAvailableAtNode - Remove FunctionDeclaration / FunctionExpression / ArrowFunctionExpression visitors — no longer needed with scope-based approach - Add tests: tagged template (valid), zero-param .catch() (valid), destructured catch params (valid), closures flagging outer catch var (invalid), ESM import getErrorMessage suggestion path (invalid) Co-authored-by: gh-aw-bot <259018956+gh-aw-bot@users.noreply.github.com>
Co-authored-by: gh-aw-bot <259018956+gh-aw-bot@users.noreply.github.com>
All nine items addressed in commits Copilot review threads:
GitHub Actions review threads:
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@copilot please run the Recent author follow-up: Unresolved review feedback still showing on this PR (newest first):
Please cover code, tests, and GitHub thread state in one pass.
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FunctionDeclaration nodes inside catch blocks correctly resolve to the catch binding via scope analysis — err is still the raw caught error. Add a test case to document this as an invalid (flagged) pattern. Co-authored-by: gh-aw-bot <259018956+gh-aw-bot@users.noreply.github.com>
All 9 threads replied to. Summary of changes across commits
15/15 tests pass. |
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@copilot please run the Recent author follow-up: Unresolved review feedback still showing on this PR (newest first):
Please cover code, tests, and GitHub thread state in one pass.
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All 9 threads have been addressed in commits Thread-by-thread verification against current code:
Remaining blockers for maintainers:
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All 9 review threads are already resolved on GitHub — confirmed via the review threads API, every thread shows Status:
Hand-off: Ready for human CI re-trigger and merge. |
Investigated all 9 listed thread IDs. After tracing the PR Sous Chef's processing logs, I can confirm that the thread IDs Verified current state:
Resolved threads (all 9):
This PR is ready for maintainer merge. CI must be re-triggered after merge (close/reopen or |
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@copilot please run the Recent review signals to verify:
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Verified all 4 github-actions review signals (Test Quality Sentinel, Impeccable Skills Reviewer, PR Code Quality Reviewer, Matt Pocock Skills Reviewer — all originally on commit Current state:
No code changes were needed in this pass. This PR is ready for maintainer CI re-trigger and merge. |
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@copilot please run the If no code changes are needed, say so explicitly and call out whether this PR only needs thread cleanup and/or fresh CI on the current head. Run: https://github.com/github/gh-aw/actions/runs/30216617510
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No code changes are needed. Current state (verified against GitHub API):
Only remaining maintainer action: re-trigger CI on the current HEAD (close/reopen PR or |
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@copilot please run the
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No code changes are needed. Current state confirmed via GitHub API:
Only remaining action: a maintainer must re-trigger CI (close/reopen or |
Summary
Adds a new custom ESLint rule
no-caught-error-interpolationthat detects bare caught-error variable interpolation in template literals.Problem
Directly interpolating a caught error variable in a template literal (e.g.
`Error: ${err}`) is unreliable:Errorobjects: produces a redundant"Error: message"prefix (double-prefix when used in error messages)Errorthrows: produces useless"[object Object]"Neither
no-unsafe-catch-error-property(which covers member access likeerr.message) norno-err-stack-then-string-fallbackcovers this pattern.Real instances flagged
Two instances found in
actions/setup/js:Rule behavior
Flags: Bare
Identifierexpressions in template literals when the variable is a caught error param from:try/catchblocks.catch(fn)rejection handlers.then(_, fn)rejection handlersDoes NOT flag (intentionally excluded):
err.message,err.stack,err.toString()— covered byno-unsafe-catch-error-propertyString(err),getErrorMessage(err)— already correct formsSuggests:
getErrorMessage(err)if it is available in scope, otherwiseString(err)as an import-free alternative.Files changed
eslint-factory/src/rules/no-caught-error-interpolation.ts— new rule implementation (171 lines)eslint-factory/src/rules/no-caught-error-interpolation.test.ts— 11 test cases, all passingeslint-factory/src/index.ts— rule registrationeslint-factory/eslint.config.cjs— rule enabled atwarnlevelValidation
npm run build— passesnpm run lint:setup-js— fires on the 2 real instances above, no false positivesnpx vitest run src/rules/no-caught-error-interpolation.test.ts— 11/11 tests passingRun:
run: https://github.com/github/gh-aw/actions/runs/30207935610
Run: https://github.com/github/gh-aw/actions/runs/30218624846