ESLint Plugin: Fix no-unused-vars-before-return JSX identifier reference

[aduth]

Fixes #16418

This pull request seeks to resolve an issue with the custom ESLint rule @wordpress/no-unused-vars-before-return where an assigned variable which is referenced in a JSX identifier as tag name would wrongly report as being an error.

Previously, the following example would have been wrongly considered as an error:

function MyComponent() {
	const Foo = getSomeComponent();
	return <Foo />;
}

Implementation Notes:

As described in the inline code documentation and in the comments of #16418, the underlying issue is that we rely on variable references provided by ESLint, which at the present time does not include references of JSX identifiers. The approach here is to manually identify and merge those identifiers when considering references.

Testing Instructions:

Ensure unit tests pass:

npm run test-unit packages/eslint-plugin/rules/__tests__/no-unused-vars-before-return.js

Ensure lint passes:

npm run lint-js

[github-actions]

Size Change: 0 B

Total Size: 842 kB

ℹ️ View Unchanged

Filename	Size	Change
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build/annotations/index.js	3.62 kB	0 B
build/api-fetch/index.js	4.01 kB	0 B
build/autop/index.js	2.82 kB	0 B
build/blob/index.js	620 B	0 B
build/block-directory/index.js	6.24 kB	0 B
build/block-directory/style-rtl.css	760 B	0 B
build/block-directory/style.css	761 B	0 B
build/block-editor/index.js	105 kB	0 B
build/block-editor/style-rtl.css	10.2 kB	0 B
build/block-editor/style.css	10.2 kB	0 B
build/block-library/editor-rtl.css	7.08 kB	0 B
build/block-library/editor.css	7.09 kB	0 B
build/block-library/index.js	112 kB	0 B
build/block-library/style-rtl.css	7.17 kB	0 B
build/block-library/style.css	7.17 kB	0 B
build/block-library/theme-rtl.css	683 B	0 B
build/block-library/theme.css	685 B	0 B
build/block-serialization-default-parser/index.js	1.88 kB	0 B
build/block-serialization-spec-parser/index.js	3.1 kB	0 B
build/blocks/index.js	57.7 kB	0 B
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build/components/style-rtl.css	16.9 kB	0 B
build/components/style.css	16.9 kB	0 B
build/compose/index.js	6.66 kB	0 B
build/core-data/index.js	11.4 kB	0 B
build/data-controls/index.js	1.25 kB	0 B
build/data/index.js	8.43 kB	0 B
build/date/index.js	5.47 kB	0 B
build/deprecated/index.js	772 B	0 B
build/dom-ready/index.js	569 B	0 B
build/dom/index.js	3.1 kB	0 B
build/edit-navigation/index.js	3.54 kB	0 B
build/edit-navigation/style-rtl.css	485 B	0 B
build/edit-navigation/style.css	485 B	0 B
build/edit-post/index.js	27.9 kB	0 B
build/edit-post/style-rtl.css	12.3 kB	0 B
build/edit-post/style.css	12.3 kB	0 B
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build/edit-site/style-rtl.css	5.05 kB	0 B
build/edit-site/style.css	5.05 kB	0 B
build/edit-widgets/index.js	7.49 kB	0 B
build/edit-widgets/style-rtl.css	4.67 kB	0 B
build/edit-widgets/style.css	4.67 kB	0 B
build/editor/editor-styles-rtl.css	428 B	0 B
build/editor/editor-styles.css	431 B	0 B
build/editor/index.js	43.3 kB	0 B
build/editor/style-rtl.css	3.48 kB	0 B
build/editor/style.css	3.47 kB	0 B
build/element/index.js	4.65 kB	0 B
build/escape-html/index.js	733 B	0 B
build/format-library/index.js	7.32 kB	0 B
build/format-library/style-rtl.css	502 B	0 B
build/format-library/style.css	502 B	0 B
build/hooks/index.js	2.13 kB	0 B
build/html-entities/index.js	622 B	0 B
build/i18n/index.js	3.56 kB	0 B
build/is-shallow-equal/index.js	711 B	0 B
build/keyboard-shortcuts/index.js	2.51 kB	0 B
build/keycodes/index.js	1.91 kB	0 B
build/list-reusable-blocks/index.js	3.12 kB	0 B
build/list-reusable-blocks/style-rtl.css	226 B	0 B
build/list-reusable-blocks/style.css	226 B	0 B
build/media-utils/index.js	5.28 kB	0 B
build/notices/index.js	1.79 kB	0 B
build/nux/index.js	3.4 kB	0 B
build/nux/style-rtl.css	616 B	0 B
build/nux/style.css	613 B	0 B
build/plugins/index.js	2.67 kB	0 B
build/primitives/index.js	1.49 kB	0 B
build/priority-queue/index.js	789 B	0 B
build/redux-routine/index.js	2.84 kB	0 B
build/rich-text/index.js	14.8 kB	0 B
build/server-side-render/index.js	2.67 kB	0 B
build/shortcode/index.js	1.7 kB	0 B
build/token-list/index.js	1.28 kB	0 B
build/url/index.js	4.02 kB	0 B
build/viewport/index.js	1.84 kB	0 B
build/warning/index.js	1.14 kB	0 B
build/wordcount/index.js	1.17 kB	0 B

_{compressed-size-action}

[aduth]

19b7f26 demonstrates how these changes fix a preexisting issue. The ESLint rule had previously been disabled (in #21354) due to this bug.

[gziolo]

Nice fix 👍

For bug fixes touching non-production code we need to iterate quicker. You shouldn’t wait so long for review 🙁