feat!: enable JSX reference tracking #20152

Pixel998 · 2025-09-23T07:37:15Z

Prerequisites checklist

I have read the contributing guidelines.

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[ ] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofix to a rule
[ ] Add a CLI option
[x] Add something to the core
[ ] Other, please explain:

This PR enables JSX reference tracking in ESLint by passing the jsx option to eslint-scope. This feature was already implemented in eslint-scope but wasn't being utilized in ESLint.

What changes did you make? (Give an overview)

Modified lib/languages/js/index.js and lib/linter/linter.js to pass jsx: ecmaFeatures.jsx to the scope analyzer
Added tests for no-undef rule to verify JSX element references are properly tracked
Added tests for no-use-before-define rule to verify JSX usage follows definition order rules

Fixes #19495

Is there anything you'd like reviewers to focus on?

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JoshuaKGoldberg

🚀 LGTM, thanks! I couldn't find any other uses that need to be updated. But I'm not a deep expert here and should defer to a second review.

github-actions · 2025-10-05T22:32:23Z

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aladdin-add

LGTM, thanks!

mdjermanovic · 2025-11-17T19:51:14Z

I think we should update docs here, as Reference#identifier can now also be a JSXIdentifier node:

eslint/docs/src/extend/scope-manager-interface.md

Lines 274 to 277 in a463e7b

    
           #### identifier 
        
           - **Type:** `ASTNode` 
        
           - **Description:** The `Identifier` node of this reference.

And types:

eslint/lib/types/index.d.ts

Lines 179 to 180 in a463e7b

    
           interface Reference { 
        
           	identifier: ESTree.Identifier;

mdjermanovic · 2025-11-18T08:24:05Z

I think we could also update the no-useless-assignment rule to include variables that have JSXIdentifier in checking:

eslint/lib/rules/no-useless-assignment.js

Lines 338 to 348 in 3383e7e

    
           				if ( 
        
           					targetAssignment.variable.references.some( 
        
           						ref => ref.identifier.type !== "Identifier", 
        
           					) 
        
           				) { 
        
           					/** 
        
           					 * Skip checking for a variable that has at least one non-identifier reference. 
        
           					 * It's generated by plugins and cannot be handled reliably in the core rule. 
        
           					 */ 
        
           					return; 
        
           				}

eslint/lib/rules/no-useless-assignment.js

Line 532 in 3383e7e

Identifier(node) {

Pixel998 · 2025-11-25T13:26:04Z

I’ve updated the scope manager documentation, the no-useless-assignment rule, and the migration guide. For the type update, we can either define JSXIdentifier inline:

interface JSXIdentifier extends ESTree.BaseNode {
    type: "JSXIdentifier";
    name: string;
}

or use an existing type package such as @types/estree-jsx. What do you think?

mdjermanovic · 2025-11-25T16:42:25Z

I’ve updated the scope manager documentation, the no-useless-assignment rule, and the migration guide. For the type update, we can either define JSXIdentifier inline:
interface JSXIdentifier extends ESTree.BaseNode {
    type: "JSXIdentifier";
    name: string;
}
or use an existing type package such as @types/estree-jsx. What do you think?

I think an inline definition would be fine, but would like @fasttime's opinion as this should probably be aligned with eslint/js#709 (and we'll eventually just re-export types from eslint-scope here?).

fasttime · 2025-11-25T21:28:33Z

I think an inline definition would be fine, but would like @fasttime's opinion as this should probably be aligned with eslint/js#709 (and we'll eventually just re-export types from eslint-scope here?).

I also think an inline definition should be fine. ESLint doesn’t import types from eslint-scope, in fact, the opposite is true for historical reasons. But since the JSXIdentifier type definition is small, we could define it in both ESLint and eslint-scope for now, and later consider moving it to a more appropriate location (for example the Espree types).

Pixel998 · 2025-11-26T13:10:11Z

I’ve updated the type accordingly. This should now be ready for review.

docs/src/use/migrate-to-10.0.0.md

lib/rules/no-useless-assignment.js

tests/lib/rules/no-useless-assignment.js

docs/src/use/migrate-to-10.0.0.md

lib/rules/no-useless-assignment.js

DMartens · 2025-12-01T20:14:14Z

Changes overall LGTM, thanks.
Maybe we should also add some basic tests for the rule no-unused-vars.

tests/lib/rules/no-useless-assignment.js

mdjermanovic

LGTM, thanks! Leaving open for @nzakas to verify.

snitin315

LGTM, thanks! Left an optional suggestion.

snitin315 · 2025-12-05T16:46:55Z

docs/src/use/migrate-to-10.0.0.md

+}
+```
+
+Prior to v10.0.0, ESLint did not recognize that `<Card>` is a reference to the imported `Card`, which could result in false positives such as reporting `Card` as "defined but never used" ([`no-unused-vars`](../rules/no-unused-vars)) or false negatives such as failing to report `Card` as undefined ([`no-undef`](../rules/no-undef)) if the import is removed. Starting with v10.0.0, `<Card>` is treated as a normal reference to the variable in scope. This brings JSX handling in line with developer expectations and improves the linting experience for modern JavaScript applications using JSX.


Suggested change

Prior to v10.0.0, ESLint did not recognize that `<Card>` is a reference to the imported `Card`, which could result in false positives such as reporting `Card` as "defined but never used" ([`no-unused-vars`](../rules/no-unused-vars)) or false negatives such as failing to report `Card` as undefined ([`no-undef`](../rules/no-undef)) if the import is removed. Starting with v10.0.0, `<Card>` is treated as a normal reference to the variable in scope. This brings JSX handling in line with developer expectations and improves the linting experience for modern JavaScript applications using JSX.

Prior to v10.0.0, ESLint did not recognize that `<Card>` is a reference to the imported `Card`, which could result in false positives such as reporting `Card` as "defined but never used" ([`no-unused-vars`](../rules/no-unused-vars)) or false negatives such as failing to report `Card` as undefined ([`no-undef`](../rules/no-undef)) if the import is removed. Starting with v10.0.0, `<Card>` is treated as a normal reference to the variable in scope. This brings JSX handling in line with developer expectations and enhances the linting experience for modern JavaScript applications that use JSX.

nzakas

LGTM. Thanks!

feat!: enable JSX reference tracking

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github-project-automation bot added this to Triage Sep 23, 2025

github-project-automation bot moved this to Needs Triage in Triage Sep 23, 2025

eslint-github-bot bot added breaking This change is backwards-incompatible feature This change adds a new feature to ESLint labels Sep 23, 2025

eslint-github-bot bot mentioned this pull request Sep 23, 2025

Change Request: Enable JSX reference tracking #19495

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Pixel998 added 2 commits November 25, 2025 11:49

Merge branch 'main' into enable-jsx-reference-tracking

9914454

apply suggestions and update migration guide

d441611

Pixel998 dismissed stale reviews from aladdin-add and JoshuaKGoldberg via d441611 November 25, 2025 13:20

github-actions bot added the rule Relates to ESLint's core rules label Nov 25, 2025

update Reference.identifier type to include JSXIdentifier

6305105

Pixel998 marked this pull request as ready for review November 26, 2025 13:09

Pixel998 requested a review from a team as a code owner November 26, 2025 13:09

mdjermanovic reviewed Nov 26, 2025

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Pixel998 added 4 commits December 3, 2025 04:51

apply suggestions

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add tests for no-unused-vars rule

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simplify selector

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nzakas approved these changes Dec 8, 2025

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nzakas merged commit c7046e6 into eslint:main Dec 8, 2025
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feat!: enable JSX reference tracking #20152

feat!: enable JSX reference tracking #20152

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Pixel998 commented Sep 23, 2025

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