refactor(eslint-plugin-mobx): rewrite in TypeScript and type flat/legacy configs

[rakleed]

Rewrites eslint-plugin-mobx in TypeScript so mobx.flatConfigs.recommended and mobx.configs.recommended are typed when consumed from a TypeScript eslint.config.ts, per @kubk's suggestion:

• Source files renamed to .ts.
• Rollup now compiles src/index.ts with rollup-plugin-typescript2 (already used by the other packages in this monorepo). Babel still runs afterwards (via the existing .babelrc.js) so the shipped bundle is downleveled the same way it was before this change.
• Declarations are generated into dist/index.d.ts and "types" points there, so the declaration can no longer drift from the implementation the way a hand-written one could. The generated export default is patched to export = after the build to match the actual module.exports = <value> CommonJS runtime shape regardless of the consumer's esModuleInterop setting, and the standalone .d.ts rollup-plugin-typescript2 emits per compiled module is removed since dist/index.d.ts is fully self-contained.
• @types/eslint moved to dependencies (it's referenced by the generated declaration, so it needs to be installed for consumers too), and @types/estree is pinned to ^1.0.0 as a direct dependency, since @types/eslint's own dependency on it is unconstrained.

Closes #4545.

Code change checklist

• Added/updated unit tests
• Updated /docs. For new functionality, at least API.md should be updated
• Verified that there is no significant performance drop (npm -w mobx run test:performance)

[changeset-bot]

🦋 Changeset detected

Latest commit: 4971f60

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
eslint-plugin-mobx	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

[kubk]

Hi @rakleed Thank you for the PR

the issue I see here is that we need to maintain JSDoc + a handwritten declaration file. Thoughts on rewriting the eslint plugin to TS?

the eslint plugin is already bundled with rollup. Possible plan:

1. Rename the source files to .ts
2. Change the Rollup input to src/index.ts
3. Add rollup-plugin-typescript2, which the monorepo already uses
4. Generate declarations into dist
5. Set "types": "dist/index.d.ts"

[Copilot]

🟡 Changes recommended

Public type dependencies and generated declaration behavior are not packaged or tested correctly, and the implementation contradicts the stated scope.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds typings for the ESLint plugin’s legacy and flat recommended configurations by migrating its implementation to TypeScript and generating declarations during Rollup builds.

Changes:

• Types plugin rules and recommended configurations.
• Replaces JavaScript sources with TypeScript and updates build/test configuration.
• Adds package metadata and release notes for declarations.

File summaries

File	Description
.changeset/eslint-plugin-mobx-flat-config-types.md	Records the typing enhancement.
package-lock.json	Locks the ESLint type dependency.
packages/eslint-plugin-mobx/package.json	Declares typings and type-check scripts.
packages/eslint-plugin-mobx/rollup.config.js	Switches the build to TypeScript.
packages/eslint-plugin-mobx/tsconfig.json	Configures source type-checking.
packages/eslint-plugin-mobx/src/index.ts	Types and exports plugin configurations.
packages/eslint-plugin-mobx/src/index.js	Removes the previous JavaScript entry point.
packages/eslint-plugin-mobx/src/utils.ts	Migrates shared utilities to TypeScript.
packages/eslint-plugin-mobx/src/utils.js	Removes the JavaScript utilities.
packages/eslint-plugin-mobx/src/exhaustive-make-observable.ts	Types the exhaustive rule.
packages/eslint-plugin-mobx/src/missing-make-observable.ts	Migrates and types the rule.
packages/eslint-plugin-mobx/src/missing-make-observable.js	Removes the JavaScript rule.
packages/eslint-plugin-mobx/src/missing-observer.ts	Types the observer rule.
packages/eslint-plugin-mobx/src/no-anonymous-observer.ts	Types the anonymous-observer rule.
packages/eslint-plugin-mobx/src/unconditional-make-observable.ts	Migrates and types the rule.
packages/eslint-plugin-mobx/src/unconditional-make-observable.js	Removes the JavaScript rule.
packages/eslint-plugin-mobx/__tests__/exhaustive-make-observable.js	Updates TypeScript source imports.
packages/eslint-plugin-mobx/__tests__/missing-make-observable.js	Updates imports and formatting.
packages/eslint-plugin-mobx/__tests__/missing-observer.js	Updates the rule import.
packages/eslint-plugin-mobx/__tests__/no-anonymous-observer.js	Updates the rule import.
packages/eslint-plugin-mobx/__tests__/unconditional-make-observable.js	Updates imports and formatting.

Review details

Suppressed comments (1)

packages/eslint-plugin-mobx/src/exhaustive-make-observable.ts:121

• “Listen” is the wrong form here; the fields are being “listed.”

• Files reviewed: 20/21 changed files
• Comments generated: 4
• Review effort level: Balanced

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[kubk]

@rakleed Thank you! could you please use git mv so git doesn't re-create files from scratch and we can see what really changed?

Same for missing-make-observable