fix(lint): noArrayIndexKey should flag index anywhere in template by LouisLau-art · Pull Request #8968 · biomejs/biome

LouisLau-art · 2026-02-05T02:42:54Z

Summary

lint/suspicious/noArrayIndexKey previously only tracked the last identifier found in a template/binary expression (and could skip reporting when templates mixed identifier and non-identifier expressions).

This update collects all reference identifiers from key expressions (template, binary, parenthesized) and reports when any of them resolves to the array-index parameter.

Added test coverage for cases like:

key={`${index}-${item}`}
key={`${item.title}-${index}`}
key={index + item}

AI assistance notice: this PR was prepared with AI assistance and manually verified before submission.

Test Plan

cargo test -p biome_js_analyze -- no_array_index_key
cargo test -p biome_js_formatter

Docs

No docs change required; this is a behavior fix for an existing lint rule.

changeset-bot · 2026-02-05T02:42:59Z

🦋 Changeset detected

Latest commit: eee9cf9

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.

Click here if you're a maintainer who wants to add another changeset to this PR

coderabbitai · 2026-02-05T02:47:03Z

No actionable comments were generated in the recent review. 🎉

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Reviewing files that changed from the base of the PR and between 399cb54 and eee9cf9.

📒 Files selected for processing (1)

.changeset/no-array-index-key-template-order.md

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

.changeset/no-array-index-key-template-order.md

Walkthrough

Reworks the noArrayIndexKey lint to gather multiple candidate identifiers from key expressions (identifiers, template literals, binary expressions, parenthesised expressions) via a new collect_reference_identifiers routine. Each candidate is resolved to a function parameter and traced to its containing call expression to check whether it represents an array index (is_array_method_index). Retains the React.cloneElement diagnostic path, removes the previous recursive cap_array_index_value traversal, simplifies control flow with early continues, and adds tests covering template and binary key expressions that include the index. Adds a changelog entry for the fix.

Suggested reviewers

ematipico
Netail

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main fix: the noArrayIndexKey lint rule now flags index usage anywhere in templates, not just the last position.
Description check	✅ Passed	The description clearly explains the fix, references issue `#8812`, and outlines the test coverage and approach taken.
Linked Issues check	✅ Passed	The changes fully address issue `#8812` by collecting all reference identifiers from key expressions and detecting array-index usage anywhere in templates or binary expressions.
Out of Scope Changes check	✅ Passed	All changes are tightly scoped to fixing noArrayIndexKey detection: updated rule logic, expanded test cases, and added changelog entry.

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dyc3 · 2026-02-06T23:22:10Z

Please add a changeset and restore our PR template

codspeed-hq · 2026-02-06T23:36:32Z

Merging this PR will not alter performance

✅ 58 untouched benchmarks
⏩ 95 skipped benchmarks¹

_{Comparing LouisLau-art:fix/noArrayIndexKey-template-order (eee9cf9) with main (db0da5c)}

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. ↩

LouisLau-art · 2026-02-09T00:40:32Z

Thanks for the reminder. I’ll add a changeset and restore the PR template format in this PR.

LouisLau-art · 2026-02-09T00:45:02Z

Addressed both points: I added a changeset in this branch and restored the PR description structure using the project PR template sections (Summary/Test Plan/Docs).

dyc3

Looks good. Just fix the lints from clippy

LouisLau-art · 2026-02-11T02:19:43Z

Thanks, I’ll take care of the remaining Clippy lints in a follow-up commit.

coderabbitai

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@crates/biome_js_analyze/src/lint/suspicious/no_array_index_key.rs`:
- Around line 175-176: The code currently uses the `?` operator on
`is_array_method_index(&parameter, &call_expression)` inside `run`, which causes
`run` to return early when that helper yields `None` (non-array contexts) and
skips later candidates; change this to explicitly handle the Option: call
`is_array_method_index(&parameter, &call_expression)` and `match`/`if let
Some(is_index) = ...` (or `if let None = ... { continue; }`) and only bail out
when it returns `Some(false)`/`true` per your logic, otherwise `continue` to the
next candidate so non-array contexts do not abort the whole analysis. Ensure you
update the branch around the current `if !is_array_method_index(...)? {
continue; }` to use this explicit handling.

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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📥 Commits

Reviewing files that changed from the base of the PR and between 93789c6 and 399cb54.

📒 Files selected for processing (1)

crates/biome_js_analyze/src/lint/suspicious/no_array_index_key.rs

coderabbitai · 2026-02-28T17:27:51Z

crates/biome_js_analyze/src/lint/suspicious/no_array_index_key.rs

+            if !is_array_method_index(&parameter, &call_expression)? {
+                continue;


⚠️ Potential issue | 🟠 Major

Avoid bailing out the whole analysis on non-array candidates.

At Line 175, is_array_method_index(...)? returns None for non-array call contexts and exits run early, so later candidates in the same key expression are never checked. That can still miss a real index reference.

Suggested fix

- if !is_array_method_index(&parameter, &call_expression)? { - continue; - } + let Some(is_index_parameter) = is_array_method_index(&parameter, &call_expression) + else { + continue; + }; + if !is_index_parameter { + continue; + }

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

if !is_array_method_index(&parameter, &call_expression)? {

continue;

let Some(is_index_parameter) = is_array_method_index(&parameter, &call_expression)

else {

continue;

};

if !is_index_parameter {

continue;

}

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed. In `@crates/biome_js_analyze/src/lint/suspicious/no_array_index_key.rs` around lines 175 - 176, The code currently uses the `?` operator on `is_array_method_index(&parameter, &call_expression)` inside `run`, which causes `run` to return early when that helper yields `None` (non-array contexts) and skips later candidates; change this to explicitly handle the Option: call `is_array_method_index(&parameter, &call_expression)` and `match`/`if let Some(is_index) = ...` (or `if let None = ... { continue; }`) and only bail out when it returns `Some(false)`/`true` per your logic, otherwise `continue` to the next candidate so non-array contexts do not abort the whole analysis. Ensure you update the branch around the current `if !is_array_method_index(...)? { continue; }` to use this explicit handling.

fix(lint): catch array index key in templates

9f744e7

LouisLau-art mentioned this pull request Feb 5, 2026

💅 lint/suspicious/noArrayIndexKey false negative when re-ordering value and index in template string #8812

Closed

1 task

github-actions bot added A-Linter Area: linter L-JavaScript Language: JavaScript and super languages labels Feb 5, 2026

chore(changeset): add release note for noArrayIndexKey fix

93789c6

dyc3 approved these changes Feb 10, 2026

View reviewed changes

This was referenced Feb 28, 2026

fix(linter): handle re-ordered index in template string for noArrayIndexKey #9237

Closed

fix(lint): detect array index in all positions of template strings #9271

Closed

dyc3 self-assigned this Feb 28, 2026

dyc3 added 2 commits February 28, 2026 12:22

chore: fix lints

399cb54

chore: fix changeset

eee9cf9

coderabbitai bot reviewed Feb 28, 2026

View reviewed changes

dyc3 merged commit a2b4494 into biomejs:main Feb 28, 2026
18 checks passed

github-actions bot mentioned this pull request Feb 28, 2026

ci: release #9188

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fix(lint): noArrayIndexKey should flag index anywhere in template#8968

fix(lint): noArrayIndexKey should flag index anywhere in template#8968
dyc3 merged 4 commits intobiomejs:mainfrom
LouisLau-art:fix/noArrayIndexKey-template-order

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