feat(biome_js_analyze): implement `noEqualsToNull` rule #8214

hirokiokada77 · 2025-11-22T12:37:48Z

Summary

This PR adds the noEqualsToNull rule, which enforces the use of === and !== for comparison with null instead of == or !=.

Closes #8195.

Test Plan

Added:

crates/biome_js_analyze/tests/specs/nursery/noEqualsToNull/invalid.js
crates/biome_js_analyze/tests/specs/nursery/noEqualsToNull/invalid.js.snap
crates/biome_js_analyze/tests/specs/nursery/noEqualsToNull/valid.js
crates/biome_js_analyze/tests/specs/nursery/noEqualsToNull/valid.js.snap

changeset-bot · 2025-11-22T12:37:54Z

🦋 Changeset detected

Latest commit: 73859c6

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

Not sure what this means? Click here to learn what changesets are.

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coderabbitai · 2025-11-22T12:41:13Z

Walkthrough

This pull request introduces a new linter rule noEqualsToNull that detects loose equality comparisons (== and !=) with null literals and suggests strict equality alternatives (=== and !==). The implementation includes the core lint rule, configuration options, test cases covering both invalid and valid patterns, and a changelog entry documenting the addition.

Suggested labels

A-Project, A-Linter, L-JavaScript, A-Diagnostic

Suggested reviewers

dyc3
ematipico

Pre-merge checks and finishing touches

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarises the main change: implementing a new noEqualsToNull linter rule.
Description check	✅ Passed	The description is directly related to the changeset, explaining what the rule does and referencing the closed issue.
Linked Issues check	✅ Passed	The PR successfully implements the noEqualsToNull rule as requested in issue #8195, porting ESLint's no-eq-null rule.
Out of Scope Changes check	✅ Passed	All changes are scoped to implementing the noEqualsToNull rule with necessary test files and rule options.

✨ Finishing touches

📝 Generate docstrings

🧪 Generate unit tests (beta)

Create PR with unit tests
Post copyable unit tests in a comment

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Actionable comments posted: 0

🧹 Nitpick comments (1)

crates/biome_js_analyze/tests/specs/nursery/noEqualsToNull/invalid.js (1)
1-3: Consider testing reversed order.

The tests only show foo == null and foo != null, but the rule implementation also handles null == foo and null != foo. Adding reversed order cases would demonstrate comprehensive coverage.
 /* should generate diagnostics */
 foo == null;
 foo != null;
+null == foo;
+null != foo;

📜 Review details

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 182ecdc and a8116b0.

⛔ Files ignored due to path filters (7)

crates/biome_configuration/src/analyzer/linter/rules.rs is excluded by !**/rules.rs and included by **
crates/biome_diagnostics_categories/src/categories.rs is excluded by !**/categories.rs and included by **
crates/biome_js_analyze/src/lint/nursery.rs is excluded by !**/nursery.rs and included by **
crates/biome_js_analyze/tests/specs/nursery/noEqualsToNull/invalid.js.snap is excluded by !**/*.snap and included by **
crates/biome_js_analyze/tests/specs/nursery/noEqualsToNull/valid.js.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 (6)

.changeset/legal-rice-clean.md (1 hunks)
crates/biome_js_analyze/src/lint/nursery/no_equals_to_null.rs (1 hunks)
crates/biome_js_analyze/tests/specs/nursery/noEqualsToNull/invalid.js (1 hunks)
crates/biome_js_analyze/tests/specs/nursery/noEqualsToNull/valid.js (1 hunks)
crates/biome_rule_options/src/lib.rs (1 hunks)
crates/biome_rule_options/src/no_equals_to_null.rs (1 hunks)

🧰 Additional context used

🧠 Learnings (1)

📚 Learning: 2025-11-21T01:10:53.036Z

Learnt from: dyc3
Repo: biomejs/biome PR: 8171
File: crates/biome_js_analyze/src/lint/nursery/no_leaked_render.rs:125-137
Timestamp: 2025-11-21T01:10:53.036Z
Learning: In the Biome codebase, each lint rule has its own options type declaration (e.g., `type Options = RuleNameOptions`) as part of the codegen process, even if the options struct is empty or unused. This is standard practice and should not be flagged as an issue.

Applied to files:

crates/biome_rule_options/src/no_equals_to_null.rs

🧬 Code graph analysis (1)

crates/biome_js_analyze/src/lint/nursery/no_equals_to_null.rs (1)

crates/biome_analyze/src/rule.rs (3)

sources (617-620)

same (246-251)

recommended (602-605)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (13)

GitHub Check: Test Node.js API
GitHub Check: Test (depot-windows-2022-16)
GitHub Check: Test (depot-ubuntu-24.04-arm-16)
GitHub Check: Check JS Files
GitHub Check: Documentation
GitHub Check: Lint project (depot-windows-2022)
GitHub Check: Check Dependencies
GitHub Check: Bench (biome_js_analyze)
GitHub Check: Bench (biome_js_formatter)
GitHub Check: Lint project (depot-ubuntu-24.04-arm-16)
GitHub Check: autofix
GitHub Check: Bench (biome_js_parser)
GitHub Check: Bench (biome_configuration)

🔇 Additional comments (10)

crates/biome_rule_options/src/lib.rs (1)

76-76: LGTM!

Standard module declaration, correctly positioned alphabetically.

.changeset/legal-rice-clean.md (1)

1-19: LGTM!

Clear, well-formatted changelog entry with accurate examples.

crates/biome_js_analyze/tests/specs/nursery/noEqualsToNull/valid.js (1)

1-3: LGTM!

Appropriate test cases for strict equality comparisons with null.

crates/biome_rule_options/src/no_equals_to_null.rs (1)

1-6: LGTM!

Standard options struct following the codebase pattern. Based on learnings.

crates/biome_js_analyze/src/lint/nursery/no_equals_to_null.rs (6)

1-14: LGTM!

Appropriate imports for the rule implementation.

16-52: LGTM!

Well-documented rule with appropriate metadata. The Unsafe fix kind correctly reflects that changing == to === can alter behaviour (e.g., null == undefined vs null === undefined).

60-71: LGTM!

Detection logic correctly identifies loose equality operators with null on either side.

73-82: LGTM!

Clear diagnostic message that highlights the problematic operator.

99-106: LGTM!

Helper function correctly identifies null literals via pattern matching.

84-96: LGTM!

Correct fix logic replacing == with === and != with !==. The action message clearly describes the change.

codspeed-hq · 2025-11-22T12:49:16Z

CodSpeed Performance Report

Merging #8214 will not alter performance

_{Comparing hirokiokada77:feat/no-equals-to-null (73859c6) with main (182ecdc)}

Summary

✅ 58 untouched
⏩ 95 skipped¹

95 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. ↩

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

feat(biome_js_analyze): implement noEqualsToNull rule

a8116b0

github-actions bot added A-Project Area: project A-Linter Area: linter L-JavaScript Language: JavaScript and super languages A-Diagnostic Area: diagnostocis labels Nov 22, 2025

coderabbitai bot reviewed Nov 22, 2025

View reviewed changes

[autofix.ci] apply automated fixes

73859c6

github-actions bot added the A-CLI Area: CLI label Nov 22, 2025

dyc3 approved these changes Nov 22, 2025

View reviewed changes

dyc3 added this pull request to the merge queue Nov 22, 2025

Merged via the queue into biomejs:main with commit 68c052e Nov 22, 2025
20 checks passed

github-actions bot mentioned this pull request Nov 22, 2025

ci: release #8189

Merged

hirokiokada77 deleted the feat/no-equals-to-null branch November 22, 2025 16:37

github-actions bot mentioned this pull request Nov 25, 2025

ci: release #8263

Merged

l0ngvh pushed a commit to l0ngvh/biome that referenced this pull request Dec 21, 2025

feat(biome_js_analyze): implement noEqualsToNull rule (biomejs#8214)

d653d1d

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

coderabbitai bot mentioned this pull request Dec 21, 2025

fix(analyzer): nursery rules diagnostics #8523

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hirokiokada77 commented Nov 22, 2025

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