feat(lint): add ignoreBooleanCoercion option to useNullishCoalescing by pkallos · Pull Request #10595 · biomejs/biome

pkallos · 2026-06-09T01:06:27Z

This PR was created with AI assistance.

Summary

adds the ignoreBooleanCoercion option to useNullishCoalescing, partially addressing #9232. this follows on from #9974 which added ignoreMixedLogicalExpressions.

when enabled, || and ||= are not reported if the value is boolean-coerced by an enclosing Boolean() call, since coalescing on falsy values is intentional in that spot. i kept the scope to just this one option so it stays easy to review. the remaining options from #9232 (ignorePrimitives, ignoreIfStatements) can come as separate PRs.

the detection mirrors how the merged mixed-logical code reads: a small typed helper that scans ancestors, skips parens and logical parents (both || and &&, since the coerced value still flows into the call), and then checks the first other ancestor is the argument of a Boolean() call.

Test Plan

the spec snapshots cover this, but if you want to check it by hand:

drop a biome.json enabling the rule and option:

{ "linter": { "rules": { "nursery": { "useNullishCoalescing": { "level": "error", "options": { "ignoreBooleanCoercion": true } } } } } }

make a test.ts:

declare const a: string | null;
declare const b: string;
declare function identity<T>(v: T): T;

const r1 = Boolean(a || b);        // quiet
const r2 = Boolean(a || b || b);   // quiet (chained)
const r3 = Boolean(b && (a || b)); // quiet (&& inside Boolean)
const r4 = a || b;                 // reports
const r5 = identity(a || b);       // reports (not a Boolean call)

run biome lint test.ts. only r4 and r5 should report.
flip the option to false and re-run. now r1, r2, r3 should report too.

things worth poking at for coverage:

||= inside Boolean() (e.g. Boolean(x ||= y)) should be quiet when the option is on
the non-Boolean callee (identity(...)) should still report, to confirm it's keyed on the Boolean name and not just "any call"
new Boolean(a || b) still reports. i think that's right since it constructs an object rather than coercing, but worth a sanity check

Docs

the option is documented in the rule's rustdoc with invalid/valid examples and validated by rules_check. no website PR needed while the rule is in nursery.

- suppresses || and ||= when the value is boolean-coerced by an enclosing Boolean() call - walks out through parens and logical parents, so chained and && cases inside Boolean() are covered too - partially addresses biomejs#9232, follows on from biomejs#9974

changeset-bot · 2026-06-09T01:06:31Z

🦋 Changeset detected

Latest commit: b6d02d6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 13 packages

Name	Type
@biomejs/biome	Patch
@biomejs/cli-win32-x64	Patch
@biomejs/cli-win32-arm64	Patch
@biomejs/cli-darwin-x64	Patch
@biomejs/cli-darwin-arm64	Patch
@biomejs/cli-linux-x64	Patch
@biomejs/cli-linux-arm64	Patch
@biomejs/cli-linux-x64-musl	Patch
@biomejs/cli-linux-arm64-musl	Patch
@biomejs/wasm-web	Patch
@biomejs/wasm-bundler	Patch
@biomejs/wasm-nodejs	Patch
@biomejs/backend-jsonrpc	Patch

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github-actions · 2026-06-09T01:06:35Z

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coderabbitai · 2026-06-09T01:19:56Z

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⛔ Files ignored due to path filters (4)

crates/biome_js_analyze/tests/specs/nursery/useNullishCoalescing/ignoreBooleanCoercionDisabled.ts.snap is excluded by !**/*.snap and included by **
crates/biome_js_analyze/tests/specs/nursery/useNullishCoalescing/ignoreBooleanCoercionEnabled.ts.snap is excluded by !**/*.snap and included by **
packages/@biomejs/backend-jsonrpc/src/workspace.ts is excluded by !**/backend-jsonrpc/src/workspace.ts and included by **
packages/@biomejs/biome/configuration_schema.json is excluded by !**/configuration_schema.json and included by **

📒 Files selected for processing (7)

.changeset/add-ignore-boolean-coercion.md
crates/biome_js_analyze/src/lint/nursery/use_nullish_coalescing.rs
crates/biome_js_analyze/tests/specs/nursery/useNullishCoalescing/ignoreBooleanCoercionDisabled.options.json
crates/biome_js_analyze/tests/specs/nursery/useNullishCoalescing/ignoreBooleanCoercionDisabled.ts
crates/biome_js_analyze/tests/specs/nursery/useNullishCoalescing/ignoreBooleanCoercionEnabled.options.json
crates/biome_js_analyze/tests/specs/nursery/useNullishCoalescing/ignoreBooleanCoercionEnabled.ts
crates/biome_rule_options/src/use_nullish_coalescing.rs

Walkthrough

This PR adds a new ignoreBooleanCoercion option to the useNullishCoalescing linter rule. When enabled, the rule suppresses diagnostics for || and ||= operators that appear inside a Boolean() call, recognizing intentional boolean coercion. The changes include the options schema definition, AST traversal logic to detect Boolean(...) context, early-exit guards in both logical-or and logical-or-assignment rule handlers, comprehensive test fixtures for both enabled and disabled configurations, and a changeset documenting the release.

Possibly related issues

#9842: Requests semantic resolution of the Boolean callee to distinguish global built-ins from shadowed identifiers, building on the detection logic introduced here.

Possibly related PRs

biomejs/biome#9974: Modifies the same useNullishCoalescing rule handlers with a similar option-gated early-exit pattern for ignoreMixedLogicalExpressions, suggesting a shared pattern for rule refinement.

Suggested labels

A-Linter, L-JavaScript

Suggested reviewers

ematipico
dyc3

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: adding the ignoreBooleanCoercion option to the useNullishCoalescing linter rule.
Description check	✅ Passed	The description clearly relates to the changeset, detailing the new option's purpose, implementation approach, test coverage, and manual verification steps.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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codspeed-hq · 2026-06-09T01:24:17Z

Merging this PR will not alter performance

✅ 58 untouched benchmarks
⏩ 196 skipped benchmarks¹

_{Comparing pkallos:pk/use-nullish-coalescing-ignore-boolean-coercion (b6d02d6) with main (a4a294c)}

196 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

github-actions Bot added A-Linter Area: linter L-JavaScript Language: JavaScript and super languages labels Jun 9, 2026

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feat(lint): add ignoreBooleanCoercion option to useNullishCoalescing#10595

feat(lint): add ignoreBooleanCoercion option to useNullishCoalescing#10595
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pkallos commented Jun 9, 2026

Summary

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codspeed-hq Bot commented Jun 9, 2026

Merging this PR will not alter performance

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