JS: Improve useless-expression query to avoid duplicate alerts on compound expressions
#19579
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Pull Request Overview
Enhance the isDomProperty predicate to detect property reads on DOM nodes (e.g., offsetHeight, clientWidth) and reduce false positives in the js/useless-expression query.
- Extend
isDomPropertyto also match property names accessed via data-flow property reads. - Add a test case validating layout-affecting reads on DOM elements.
- Record the change in the project’s change notes.
Reviewed Changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| javascript/ql/lib/Expressions/DOMProperties.qll | Extend isDomProperty predicate with a DataFlow::SourceNode branch. |
| javascript/ql/test/query-tests/Expressions/ExprHasNoEffect/dom.js | New test verifying that reads like offsetHeight and clientWidth are side-effectful. |
| javascript/ql/lib/change-notes/2025-05-26-dom-property-access.md | Add change note documenting the enhancement to isDomProperty. |
Comments suppressed due to low confidence (1)
javascript/ql/lib/Expressions/DOMProperties.qll:14
- [nitpick] The variable name
domNodeimplies a DOM AST node but actually refers to a data-flow source; consider renaming it tosourceNodeorpropSourceNodefor clearer intent.
exists(DataFlow::SourceNode domNode | isDomNode(domNode) |
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isDomPropertyuseless-expression query to avoid duplicate alerts on compound expressions
asgerf
reviewed
Jun 2, 2025
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asgerf
reviewed
Jun 10, 2025
Co-authored-by: Asger F <asgerf@github.com>
Co-authored-by: Asger F <asgerf@github.com>
Co-Authored-By: Asger F <316427+asgerf@users.noreply.github.com>
asgerf
approved these changes
Jun 10, 2025
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This PR improves the
js/useless-expressionquery by adding logic to avoid flagging compound expressions that may contain sub-expressions with side effects.