Support React components wrapped by 'mobx-react'

[asgerf]

Adds support for React components that are wrapped by observer from mobx-react or mobx-react-lite, e.g:

import { observer } from "mobx-react-lite";

const TodoView = observer(({ todo }) => <div>{todo.title}</div>)

[Copilot]

Pull request overview

This pull request adds support for React components wrapped by the observer higher-order component from the mobx-react and mobx-react-lite packages. MobX is a popular state management library for React, and the observer HOC is used to make React components reactive to MobX observables. By treating observer as a higher-order component, CodeQL can now properly track data flow through components wrapped with this function.

Changes:

• Added observer from mobx-react and mobx-react-lite to the list of recognized higher-order component builders
• Added test coverage for components wrapped with observer from both packages
• Added a change note documenting this minor analysis improvement

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
javascript/ql/lib/semmle/javascript/frameworks/React.qll	Adds observer from mobx-react and mobx-react-lite to the higherOrderComponentBuilder predicate, treating it as a HOC that wraps React components
javascript/ql/test/library-tests/frameworks/ReactJS/higherOrderComponent.jsx	Adds test imports for observer from both packages and tests wrapping a component with both versions of observer
javascript/ql/lib/change-notes/2026-02-20-mobx-react-observer.md	Documents this as a minor analysis improvement in the change notes