perf(nursery/noFloatingPromises): skip type inference for assignment statements by BezSaharaD · Pull Request #10991 · biomejs/biome

BezSaharaD · 2026-07-19T02:09:01Z

Summary

is_handled_promise() unconditionally treats a bare assignment expression-statement (e.g. x = getPromise();) as handled, regardless of its type. That check runs after ctx.type_of_expression(&expression) -- full type inference -- meaning the inference result is computed and then simply discarded for this case. Checking for an assignment expression first (a cheap, purely syntactic check) and bailing out before the type computation skips that wasted work.

Measurement

Profiled with --profile-rules on the same large real-world project as #10990:

	cumulative rule time	worst single call
before	~52s	92ms
after	~37s (-29%)	30ms

Smaller improvement than #10990's ~4.7x, since this rule's Query (Typed<JsExpressionStatement>, statement-level only) is already much narrower than noMisusedPromises's (Typed<AnyJsExpression>, every expression) -- there was less redundant work to remove to begin with. Diagnostics are byte-identical before/after (11331 errors both times).

Testing

Added assignmentIsHandled.ts as a new regression fixture (generated its snapshot via INSTA_UPDATE=always).
All 61 noFloatingPromises spec tests (60 existing + 1 new) pass.
All 478 tests in the nursery rule group pass unchanged.

Disclosure

Found and fixed with Claude's (Anthropic) assistance while continuing the profiling from #10990 against the same real-world project - reviewed and verified locally (unit tests, byte-identical diagnostic diff, release build) before submitting.

…statements is_handled_promise() unconditionally treats a bare assignment expression-statement as handled, regardless of its type -- so there's no need to run full type inference (ctx.type_of_expression) just to be told that afterwards. Check for an assignment expression first, before the type computation, and bail out early in that case. Measured via --profile-rules on a large real-world TypeScript/React project: this rule's cumulative cost dropped from ~52s to ~37s (~29%), and its worst-case single-call time dropped from 92ms to 30ms. Smaller than the noMisusedPromises fix in a prior PR since fewer of this rule's (already query-narrowed) invocations hit the pattern, but a real, measured improvement with byte-identical diagnostics before and after (11331 errors both times). Added a regression test fixture (assignmentIsHandled.ts) alongside the existing spec suite. All 61 rule tests (60 existing + 1 new) and all 478 nursery-group tests pass.

changeset-bot · 2026-07-19T02:09:05Z

🦋 Changeset detected

Latest commit: 990334a

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 · 2026-07-19T02:09:09Z

✅ Organic activity

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codspeed · 2026-07-19T05:57:36Z

Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 213 skipped benchmarks¹

_{Comparing BezSaharaD:fix/no-floating-promises-perf (990334a) with main (89c27c6)}

213 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. ↩

coderabbitai · 2026-07-19T11:09:22Z

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⛔ Files ignored due to path filters (1)

crates/biome_js_analyze/tests/specs/nursery/noFloatingPromises/assignmentOfArrayIsHandled.ts.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (2)

crates/biome_js_analyze/src/lint/nursery/no_floating_promises.rs
crates/biome_js_analyze/tests/specs/nursery/noFloatingPromises/assignmentOfArrayIsHandled.ts

🚧 Files skipped from review as they are similar to previous changes (1)

crates/biome_js_analyze/src/lint/nursery/no_floating_promises.rs

Walkthrough

The noFloatingPromises rule now treats assignment expressions as handled and exits before type inference or promise analysis. Documentation includes assignment examples, tests cover direct and array-of-promise assignments, and a patch changeset records the performance update.

Possibly related PRs

biomejs/biome#10934: Also changes promise handling and inferred type checks in NoFloatingPromises::run.

Suggested labels: A-Type-Inference

Suggested reviewers: dyc3

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	Clearly summarises the main change: skipping type inference for assignment statements in noFloatingPromises.
Description check	✅ Passed	The description matches the optimisation, the added fixture, and the testing/profile details.
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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Actionable comments posted: 3

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In @.changeset/perf-no-floating-promises.md:
- Line 5: Update the changeset description for noFloatingPromises to include the
required issue, rule, and assist links. Preserve the existing rule link, add the
applicable issue and assist links using the repository’s standard changeset link
format, or explicitly confirm when either link does not exist.

In `@crates/biome_js_analyze/src/lint/nursery/no_floating_promises.rs`:
- Around line 180-182: Add a rustdoc note to the no_floating_promises rule
declaration documenting that bare assignment statements are treated as handled
regardless of type. Place the documentation on the rule declaration associated
with is_handled_promise, preserving the existing internal comment and rule
behavior.
- Around line 183-188: Remove or relocate the early return for
JsAssignmentExpression in the promise analysis flow so assignments continue
through the ArrayOfPromises handling, including cases such as target =
[returnsPromise()]. Preserve the existing branch ordering and add a regression
test covering an assignment containing an array of promises.

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📥 Commits

Reviewing files that changed from the base of the PR and between bd1038b and c51f7b7.

⛔ Files ignored due to path filters (1)

crates/biome_js_analyze/tests/specs/nursery/noFloatingPromises/assignmentIsHandled.ts.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (3)

.changeset/perf-no-floating-promises.md
crates/biome_js_analyze/src/lint/nursery/no_floating_promises.rs
crates/biome_js_analyze/tests/specs/nursery/noFloatingPromises/assignmentIsHandled.ts

…gression test - Add a rustdoc bullet point and a "Valid" example showing that assigning a floating promise to a variable is considered handled (previously only explained by an internal comment). - Add assignmentOfArrayIsHandled.ts: verified that assigning the result of an array-producing call with an async callback (e.g. `target = arr.map(async (x) => ...)`) is also not flagged, and that this is unchanged by the assignment-expression bail-out (checked both with and without that bail-out; same result either way, since the assignment expression's type isn't resolved to an array type by the underlying type inference regardless). Verified: all 61 noFloatingPromises spec tests and all 480 nursery-group tests pass.

ematipico

Looks good. Do we have a case where we assign to a target and then call the target? Is that handled correctly?

ematipico · 2026-07-24T06:43:00Z

+        // `is_handled_promise` (below) always treats a bare assignment
+        // statement as handled, regardless of its type -- so there's no
+        // point paying for type inference just to be told that afterwards.


This comment is weird. Can't we just update is_handled_promise to take in consideration this new logic.

If not, just remove it. This will become the new logic

ematipico · 2026-07-24T06:44:34Z

Please remove all those comments from the new cases. Only the ones at the top are the ones that matter

BezSaharaD · 2026-07-31T00:35:23Z

Hello, I apologize for deleting the repositories. I forgot that I have open PRs. I deleted them for personal reasons and being busy with the main project. I do not claim any code or credit, but you can take the code if needed.

github-actions Bot added A-Linter Area: linter L-JavaScript Language: JavaScript and super languages labels Jul 19, 2026

BezSaharaD marked this pull request as ready for review July 19, 2026 11:05

coderabbitai Bot reviewed Jul 19, 2026

View reviewed changes

Comment thread .changeset/perf-no-floating-promises.md

Comment thread crates/biome_js_analyze/src/lint/nursery/no_floating_promises.rs

Comment thread crates/biome_js_analyze/src/lint/nursery/no_floating_promises.rs

BezSaharaD added 2 commits July 19, 2026 15:43

Merge branch 'main' into fix/no-floating-promises-perf

990334a

coderabbitai Bot mentioned this pull request Jul 23, 2026

fix(lint): avoid noFloatingPromises false positive #11067

Closed

ematipico requested changes Jul 24, 2026

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BezSaharaD closed this by deleting the head repository Jul 31, 2026

dyc3 mentioned this pull request Aug 1, 2026

perf(noFloatingPromises): short circuit assignment statements #11160

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perf(nursery/noFloatingPromises): skip type inference for assignment statements - #10991

perf(nursery/noFloatingPromises): skip type inference for assignment statements#10991
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BezSaharaD commented Jul 19, 2026

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