[🤖] Add CI job that runs the linter (ESLint), and fix some ESLint complaints in our source code (#172)

* Set up ESLint locally

Co-authored-by: OpenAI Codex <codex@openai.com>

* Add CI lint job

Co-authored-by: OpenAI Codex <codex@openai.com>

* Fix source for lint compliance

Co-authored-by: OpenAI Codex <codex@openai.com>

* Enable installed ESLint plugins

Co-authored-by: OpenAI Codex <codex@openai.com>

* Format renovate config for ESLint

Co-authored-by: OpenAI Codex <codex@openai.com>

* Update AGENTS lint guidance

Co-authored-by: OpenAI Codex <codex@openai.com>

* Remove unused npm dependencies

Co-authored-by: OpenAI Codex <codex@openai.com>

* Refresh npm lockfile

Co-authored-by: OpenAI Codex <codex@openai.com>

* Remove unused Jest toolchain

Co-authored-by: OpenAI Codex <codex@openai.com>

* Run tsc in lint command

Co-authored-by: OpenAI Codex <codex@openai.com>

* Build and check-in

---------

Co-authored-by: OpenAI Codex <codex@openai.com>

Author: DilumAluthge

.eslintrc.cjs

@@ -18,12 +18,13 @@ jobs:
     if: always() # this line is important to keep the `finalize` job from being marked as skipped; do not change or delete this line
     runs-on: ubuntu-latest
     timeout-minutes: 10
-    needs: [build, checked-in-files, example, make-targets, stalecheck-npm-install]
+    needs: [build, checked-in-files, example, lint-check, make-targets, stalecheck-npm-install]
     steps:
       - run: |
           echo build: ${{ needs.build.result }}
           echo checked-in-files: ${{ needs.checked-in-files.result }}
           echo example: ${{ needs.example.result }}
+          echo lint-check: ${{ needs.lint-check.result }}
           echo make-targets: ${{ needs.make-targets.result }}
           echo stalecheck-npm-install: ${{ needs.stalecheck-npm-install.result }}
       # The last line must NOT end with ||
@@ -33,6 +34,7 @@ jobs:
           (needs.build.result != 'success') ||
           (needs.checked-in-files.result != 'success') ||
           (needs.example.result != 'success') ||
+          (needs.lint-check.result != 'success') ||
           (needs.make-targets.result != 'success') ||
           (needs.stalecheck-npm-install.result != 'success')
   build:
@@ -167,22 +169,24 @@ jobs:
           cmd = Base.julia_cmd()
           julia_path = cmd.exec[1]
           @info "" julia_path Base.VERSION
-  # lint-check:
-  #   timeout-minutes: 30
-  #   runs-on: ubuntu-latest
-  #   strategy:
-  #     fail-fast: false
-  #   steps:
-  #       ### Check out the repo:
-  #       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
-  #         with:
-  #           persist-credentials: false
-  #       ### Install mise-en-place
-  #       - uses: jdx/mise-action@6d1e696aa24c1aa1bcc1adea0212707c71ab78a8 # v3.6.1
-  #       ### Install NodeJS (by using mise-en-place)
-  #       - run: make mise-install
-  #       ### Lint:
-  #       - run: make check-lint
+  lint-check:
+    timeout-minutes: 30
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+    steps:
+      ### Check out the repo:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      ### Install mise-en-place
+      - uses: jdx/mise-action@5228313ee0372e111a38da051671ca30fc5a96db # v3.6.3
+      ### Install NodeJS (by using mise-en-place)
+      - run: make mise-install
+      ### Install the NodeJS packages that we depend on:
+      - run: make install-packages
+      ### Lint:
+      - run: make check-lint
   make-targets: # This is a job to make sure that none of the `make` targets bitrot
     timeout-minutes: 30
     runs-on: ${{ matrix.os }}

.github/workflows/ci.yml

@@ -2,9 +2,9 @@
 
 ## Project Structure & Module Organization
 
-Core source lives in `src/` and is compiled to `lib/` with TypeScript. The GitHub Action bundle checked into releases is `dist/index.js`, generated with `tsup`. Repository metadata and runtime inputs are defined in `action.yml`. CI and integration validation live in `.github/workflows/` and `ci/test.jl`. Helper scripts are under `bin/`, and contributor notes are in `devdocs/`.
+Core source lives in `src/` and is compiled to `lib/` with TypeScript. The GitHub Action bundle checked into releases is `dist/index.cjs`, generated with `tsup`. Repository metadata and runtime inputs are defined in `action.yml`. CI and integration validation live in `.github/workflows/` and `ci/test.jl`. Helper scripts are under `bin/`, and contributor notes are in `devdocs/`.
 
-Treat `lib/` and `dist/` as generated outputs: when behavior changes in `src/`, rebuild and commit the updated artifacts. The action bundle must remain a single self-contained `dist/index.js`; if you touch the bundler config, verify runtime dependencies are not being externalized into separate files.
+Treat `lib/` and `dist/` as generated outputs: when behavior changes in `src/`, rebuild and commit the updated artifacts. The action bundle must remain a single self-contained `dist/index.cjs`; if you touch the bundler config, verify runtime dependencies are not being externalized into separate files.
 
 ## Build, Test, and Development Commands
 
@@ -13,23 +13,23 @@ Use the `Makefile` wrappers documented in `devdocs/local_setup.md`:
 - `make mise-install`: install the pinned Node.js version from `.tool-versions`.
 - `make install-packages`: install dependencies with `npm ci`.
 - `make build`: compile TypeScript from `src/` to `lib/`.
-- `make pack`: bundle the action into `dist/index.js`.
+- `make pack`: bundle the action into `dist/index.cjs`.
 - `make everything-from-scratch`: clean, reinstall, build, pack, and clean again.
 - `make clean` / `make cleanall`: remove `node_modules/`, then also `lib/` and `dist/`.
 
 ## Coding Style & Naming Conventions
 
-This project uses TypeScript with strict compiler settings from `tsconfig.json` and ESLint via `.eslintrc.cjs`. Follow the existing style: 4-space indentation, LF line endings, and simple module-level functions. Source files use lowercase names such as `juliaup.ts` and `platform.ts`; many internal helpers use snake_case names to match the current codebase.
+This project uses TypeScript with strict compiler settings from `tsconfig.json` and ESLint via `eslint.config.js`. Follow the existing style: 4-space indentation, LF line endings, and simple module-level functions. Source files use lowercase names such as `juliaup.ts` and `platform.ts`; many internal helpers use snake_case names to match the current codebase.
 
 This repo uses ESM with `moduleResolution: "NodeNext"`. Local TypeScript imports in `src/` should use explicit `.js` extensions, and `tsconfig.json` should keep compilation scoped to `src/` so tool configs do not leak into `lib/`.
 
-If you run linting manually, use `npx eslint .`. Prefer small, direct functions over abstractions.
+If you run linting manually, use `npm run lint`; it runs both `tsc --noEmit` and ESLint. Prefer small, direct functions over abstractions.
 
 ## Testing Guidelines
 
-CI currently emphasizes build correctness and end-to-end validation. The main integration check is `julia ci/test.jl`, run after the local action installs Julia on the GitHub runner. If you add TypeScript unit tests, place them beside the source or in a matching test location with names ending in `*.test.ts`; Jest is already configured in `package.json`, so `npx jest --coverage` will pick them up.
+CI currently emphasizes build correctness and end-to-end validation. The main integration check is `julia ci/test.jl`, run after the local action installs Julia on the GitHub runner. If you add TypeScript unit tests, place them beside the source or in a matching test location with names ending in `*.test.ts`, and document any new test runner setup in `package.json` and this file.
 
-Before opening a PR, run at least `make build` and `make pack`, then confirm there are no unintended diffs.
+Before opening a PR, run at least `npm run lint`, `make build`, and `make pack`, then confirm there are no unintended diffs.
 
 ## Commit & Pull Request Guidelines
 

AGENTS.md

@@ -35,9 +35,9 @@ cleanall: clean
 
 # ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
-# .PHONY: check-lint
-# check-lint:
-# 	npx eslint .
+.PHONY: check-lint
+check-lint:
+	npm run lint
 
 # .PHONY: fix-lint
 # fix-lint: