@codacy/tools-eslint-8

Table of Contents

• Overview
• Coexistence with ESLint 9
• Updating patterns
• Updating the ESLint version
• Development
• Notes for maintainers

Overview

JavaScript/TypeScript linter using ESLint 8 with the legacy config format (.eslintrc). Uses the Library execution strategy — calls the ESLint API directly rather than spawning a subprocess.

| Property | Value | | ------------- | ------------------------------------------------- | | Tool ID | ESLint8 | | Codacy UUID | f8b29663-2cb2-498d-b923-a10c6a8c05cd | | Strategy | Library | | Languages | JavaScript, TypeScript | | Dependency | eslint npm package (v8.x) + 90+ plugin packages | | Patterns | 2816 (285 core + 2531 plugin) | | File patterns | **/*.js, **/*.jsx, **/*.ts, **/*.tsx |

Coexistence with ESLint 9

This adapter coexists safely with @codacy/tools-eslint-9 in the same monorepo and the same Node.js process. Key design decisions:

• pnpm isolation: Each adapter has its own node_modules/eslint symlink pointing to a different version in the pnpm store. import("eslint") from each adapter's built output resolves to the correct version.
• Inline types: ESLint API types are defined inline (not imported from the eslint package) to avoid TypeScript declaration conflicts.
• Separate plugin registries: Plugins that need different versions for ESLint 8 vs 9 (e.g. @typescript-eslint, react-hooks) are installed at the correct version in each adapter's own dependencies.
• Lint script: Uses the root's ESLint 9 for linting source code (node ../../../node_modules/eslint/bin/eslint.js) to avoid the local ESLint 8 binary conflicting with the root's flat config.

Updating patterns

# Re-fetch pattern metadata from the Codacy API
pnpm prefetch

# Commit the result
git add src/patterns.json

Pattern IDs use the codacy-eslint encoding: _ → __, / → _. Examples:

• ESLint8_no-unused-vars (core rule)
• ESLint8_@typescript-eslint_no-unused-vars (scoped plugin)
• ESLint8_react_jsx-no-target-blank (non-scoped plugin)

Updating the ESLint version

ESLint 8 is end-of-life (October 2024). Version updates are not expected. This adapter targets the final 8.57.x release. For newer ESLint, use the eslint-9 adapter.

Development

pnpm build    # Build with tsup
pnpm test     # Run tests

Notes for maintainers

• ESLint 8 uses the legacy config format (.eslintrc.*). The adapter generates legacy config objects with plugins as string names, parser as an absolute path, and overrides for TypeScript-specific configuration.
• No executable config files: .eslintrc.js, .eslintrc.cjs, and the extensionless .eslintrc are excluded from local config detection because those formats can directly execute repo-controlled code. Only static formats (.eslintrc.yaml, .eslintrc.yml, .eslintrc.json) are detected. Note: this does not fully eliminate code execution when local configs are enabled — ESLint legacy config fields like extends and parser can still resolve to repo-controlled modules.
• Plugin resolution: resolvePluginsRelativeTo points ESLint at this adapter's package root so it finds plugins in our node_modules rather than the user's repo.
• Always-on TS parser override: A .ts/.tsx override with @typescript-eslint/parser is always created when any rules are enabled — not just when @typescript-eslint rules are present. This ensures all plugins (e.g. jsdoc) can analyze TypeScript files correctly, and that core rules like no-redeclare and no-undef are unconditionally disabled for TS files (TypeScript's compiler handles them natively).
• No project: true: The TS parser override does not use project: true because it fails when no tsconfig.json covers the target files. Most @typescript-eslint rules work without type information; type-aware rules degrade gracefully.
• Pattern IDs use the same encoding as the codacy-eslint wrapper: _ → __ then / → _ (encode), reverse for decode.
• The blacklist.ts contains rules known to crash ESLint or produce severe false positives, shared with the ESLint 9 adapter's blacklist.
• checkAvailability verifies that the loaded ESLint version starts with 8. to prevent accidental use of ESLint 9.
• install is a no-op — the npm dependency handles installation.