setup-linter

name	setup-linter
description	Set up fast conventional code linting, automatic repair, CI enforcement, and synchronous coding-agent feedback. TRIGGER when: an operator asks to add, configure, improve, or fix linting or code-quality feedback.

Setup Linter

Install a strong conventional linter, repair the existing project, and make the same repair run after every coding-agent save.

1. Inspect and agree

Inspect the ecosystem, manifests, CI, source layout, existing lint configuration, and project hook configuration. Preserve the project's established package manager and native command conventions.

Choose the ecosystem's strong conventional rules and agree the strong conventional rules with the operator before changing files. Present the evidence, exact rules, files, commands, and hook changes. Resolve consequential conflicts such as an existing CI reporter or project-owned rule whose meaning would change.

Use these defaults:

Ecosystem	Linter	Strong rules and command
JavaScript	ESLint	@eslint/js recommended; eslint .
TypeScript	ESLint	@eslint/js recommended plus typescript-eslint strictTypeChecked, parserOptions.projectService: true, and the TypeScript compiler
Elixir	Credo	mix credo --strict
Go	golangci-lint	standard plus errorlint, exhaustive, gosec, nilerr, nilnil, and wrapcheck; golangci-lint run

Read the current official documentation for the selected tool before using its API or configuration format.

2. Install and merge

Install the conventional linter with the project's package manager. Merge into existing configuration. Never replace project-owned rules, plugins, ignores, formatters, reporters, commands, CI steps, or hooks.

For JavaScript, install eslint and @eslint/js, then merge js.configs.recommended into eslint.config.mjs. For TypeScript, also install typescript-eslint, merge tseslint.configs.strictTypeChecked, set parserOptions.projectService: true, and include compiler checking in lint:code. For Elixir, add Credo to the development and test dependencies and generate .credo.exs. For Go, write or merge .golangci.yml with the listed linters enabled.

Create native project commands. In a JavaScript or TypeScript project these are:

{
  "scripts": {
    "lint:code": "eslint .",
    "lint:code:fix": "eslint . --fix"
  }
}

Use the equivalent native project command for other ecosystems. Add the non-fixing command as a required CI gate using the existing CI system and merge it without replacing other gates.

3. Install save-time feedback

Create executable .contree/hooks/lint-on-save.sh. Select the exact autofix command for the detected ecosystem rather than placing alternatives in the generated script.

JavaScript and TypeScript:

#!/usr/bin/env bash
set -euo pipefail
cd "$(git rev-parse --show-toplevel)"
if output=$(pnpm lint:code:fix 2>&1); then
  exit 0
fi
printf '%s\n' "$output" >&2
exit 2

Use the project's package manager in place of pnpm. Elixir runs mix format followed by mix credo --strict. Go runs golangci-lint run --fix.

Merge this synchronous PostToolUse group into both .claude/settings.json and .codex/hooks.json without replacing existing settings or hook entries:

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Edit|Write",
        "hooks": [
          {
            "type": "command",
            "command": "bash \"$(git rev-parse --show-toplevel)/.contree/hooks/lint-on-save.sh\"",
            "statusMessage": "Fixing lint"
          }
        ]
      }
    ]
  }
}

Keep the hook synchronous so automatic changes and failures reach the coding agent before it continues. If save-time autofix cannot complete, preserve the complete linter output, write it to stderr, and exit 2.

4. Repair and verify

Run autofix across the whole existing project. Then run the non-fixing lint command across the whole project.

Fix remaining violations directly. Do not merely list them or transfer the repair work to the operator. Preserve intended behavior and project-owned rules. Rerun lint after every repair batch until it passes.

Verify the CI gate and verify both coding-harness hooks through an actual Claude Code edit and an actual Codex edit. Do not report completion until lint passes and both save-time feedback paths have been exercised successfully.