Add smart pre-commit hooks to prevent CI failures (#1792)

* Testing skip hooks option

* Implement automatic Git hooks with Lefthook for code quality

- Replace manual hook installation with modular Lefthook configuration
- Check all changed files (staged + unstaged + untracked) for comprehensive coverage
- Add separate scripts in bin/lefthook/ for testability and maintainability
- Automatic installation via script/bootstrap and package.json postinstall
- Provide helpful error messages with fix commands and skip options
- Parallel execution of linting checks for performance

Prevents CI failures by catching linting issues locally before commits.

Author: justin808

.lefthook.yml

@@ -0,0 +1,23 @@
+# .lefthook.yml
+# Fast pre-commit hooks that check all changed files (staged + unstaged + untracked)
+# Install with: bundle exec lefthook install
+
+pre-commit:
+  parallel: true
+  commands:
+    autofix:
+      run: bin/lefthook/ruby-autofix all-changed
+
+    rubocop:
+      run: bin/lefthook/ruby-lint all-changed
+
+    prettier:
+      run: bin/lefthook/prettier-format all-changed
+
+    trailing-newlines:
+      run: bin/lefthook/check-trailing-newlines all-changed
+
+pre-push:
+  commands:
+    branch-lint:
+      run: bin/lefthook/ruby-lint branch

CLAUDE.md

@@ -12,6 +12,12 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 These requirements are non-negotiable. CI will fail if not followed.
 
+**🚀 AUTOMATIC: Git hooks are installed automatically during setup**
+
+Git hooks will automatically run linting on **all changed files (staged + unstaged + untracked)** before each commit - making it fast while preventing CI failures!
+
+**Note:** Git hooks are for React on Rails gem developers only, not for users who install the gem.
+
 ## Development Commands
 
 ### Essential Commands

CONTRIBUTING.md

@@ -7,6 +7,10 @@
 ## Prerequisites
 
 - [Yalc](https://github.com/whitecolor/yalc) must be installed globally for most local development.
+- **Git hooks setup** (automatic during normal setup):
+
+Git hooks are installed automatically when you run the standard setup commands. They will run automatic linting on **all changed files (staged + unstaged + untracked)** - making commits fast while preventing CI failures.
+
 - After updating code via Git, to prepare all examples:
 
 ```sh
@@ -457,7 +461,9 @@ This approach:
 
 ## Pre-Commit Requirements
 
-**CRITICAL**: Before committing any changes, always run the following commands to ensure code quality:
+**AUTOMATED**: If you've set up Lefthook (see Prerequisites), linting runs automatically on changed files before each commit.
+
+**MANUAL OPTION**: If you need to run linting manually:
 
 ```bash
 # Navigate to the main react_on_rails directory
@@ -476,14 +482,14 @@ rake lint:rubocop
 rake lint
 ```
 
-**Automated checks:**
+**Git hooks automatically run:**
 
-- Format all JavaScript/TypeScript files with Prettier
+- Format JavaScript/TypeScript files with Prettier (on changed files only)
 - Check and fix linting issues with ESLint
-- Check and fix Ruby style issues with RuboCop
-- Ensure all tests pass before pushing
+- Check and fix Ruby style issues with RuboCop (on all changed files)
+- Ensure trailing newlines on all files
 
-**Tip**: Set up your IDE to run these automatically on save to catch issues early.
+**Setup**: Automatic during normal development setup
 
 ## 🤖 Best Practices for AI Coding Agents
 

Gemfile.development_dependencies

@@ -38,6 +38,7 @@ group :development, :test do
   gem "rubocop-rspec", "~>2.26", require: false
   gem "scss_lint", require: false
   gem "spring", "~> 4.0"
+  gem "lefthook", require: false
 end
 
 group :test do

Gemfile.lock

@@ -156,6 +156,7 @@ GEM
     launchy (3.0.1)
       addressable (~> 2.8)
       childprocess (~> 5.0)
+    lefthook (1.13.1)
     listen (3.9.0)
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
@@ -412,6 +413,7 @@ DEPENDENCIES
   jbuilder
   jquery-rails
   launchy
+  lefthook
   listen
   package_json
   pry

bin/lefthook/check-trailing-newlines

@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+# Check for trailing newlines on all changed files
+set -euo pipefail
+
+CONTEXT="${1:-staged}"
+files="$(bin/lefthook/get-changed-files "$CONTEXT" '.*')"
+
+if [ -z "$files" ]; then
+  echo "✅ No files to check for trailing newlines"
+  exit 0
+fi
+
+if [ "$CONTEXT" = "all-changed" ]; then
+  echo "🔍 Checking trailing newlines on all changed files..."
+else
+  echo "🔍 Checking trailing newlines on $CONTEXT files..."
+fi
+
+failed_files=""
+for file in $files; do
+  if [ -f "$file" ] && [ -s "$file" ]; then
+    if ! tail -c 1 "$file" | grep -q '^$'; then
+      echo "❌ Missing trailing newline: $file"
+      failed_files="$failed_files $file"
+    fi
+  fi
+done
+
+if [ -n "$failed_files" ]; then
+  echo ""
+  echo "❌ Trailing newline check failed!"
+  echo "💡 Add trailing newlines to:$failed_files"
+  echo "🔧 Quick fix: for file in$failed_files; do echo >> \"\$file\"; done"
+  echo "🚫 Skip hook: git commit --no-verify"
+  exit 1
+fi
+
+echo "✅ All files have proper trailing newlines"

bin/lefthook/get-changed-files

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+# Get changed files based on context (staged, branch, or all)
+set -euo pipefail
+
+CONTEXT="${1:-staged}"
+PATTERN="${2:-.*}"
+
+case "$CONTEXT" in
+  staged)
+    git diff --cached --name-only --diff-filter=ACM | grep -E "$PATTERN" || true
+    ;;
+  all-changed)
+    # Get all changed files (staged + unstaged + untracked) vs working directory
+    (git diff --cached --name-only --diff-filter=ACM; git diff --name-only --diff-filter=ACM; git ls-files --others --exclude-standard) | sort -u | grep -E "$PATTERN" || true
+    ;;
+  branch)
+    # Find base branch (prefer main over master)
+    base="origin/main"
+    git rev-parse --verify --quiet "$base" >/dev/null || base="origin/master"
+    git diff --name-only --diff-filter=ACM "$base"...HEAD | grep -E "$PATTERN" || true
+    ;;
+  *)
+    echo "Usage: $0 {staged|all-changed|branch} [pattern]" >&2
+    exit 1
+    ;;
+esac

bin/lefthook/prettier-format

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+# Format JS/TS/JSON/MD files with Prettier
+set -euo pipefail
+
+CONTEXT="${1:-staged}"
+files="$(bin/lefthook/get-changed-files "$CONTEXT" '\.(js|jsx|ts|tsx|json|md|yml|yaml)$')"
+
+if [ -z "$files" ]; then
+  echo "✅ No files to format with Prettier"
+  exit 0
+fi
+
+if [ "$CONTEXT" = "all-changed" ]; then
+  echo "💅 Prettier on all changed files:"
+else
+  echo "💅 Prettier on $CONTEXT files:"
+fi
+printf "  %s\n" $files
+
+yarn run prettier --write $files
+
+# Re-stage files if running on staged or all-changed context
+if [ "$CONTEXT" = "staged" ] || [ "$CONTEXT" = "all-changed" ]; then
+  echo $files | xargs -r git add
+  echo "✅ Re-staged formatted files"
+fi

bin/lefthook/ruby-autofix

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+# Auto-fix Ruby files using rake autofix
+set -euo pipefail
+
+CONTEXT="${1:-staged}"
+files="$(bin/lefthook/get-changed-files "$CONTEXT" '\.(rb|rake|ru)$')"
+
+if [ -z "$files" ]; then
+  echo "✅ No Ruby files to autofix"
+  exit 0
+fi
+
+if [ "$CONTEXT" = "all-changed" ]; then
+  echo "🎨 Autofix on all changed Ruby files:"
+else
+  echo "🎨 Autofix on $CONTEXT Ruby files:"
+fi
+printf "  %s\n" $files
+
+bundle exec rake autofix
+
+# Re-stage files if running on staged or all-changed context
+if [ "$CONTEXT" = "staged" ] || [ "$CONTEXT" = "all-changed" ]; then
+  echo $files | xargs -r git add
+  echo "✅ Re-staged formatted files"
+fi

bin/lefthook/ruby-lint

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+# Lint Ruby files with RuboCop
+set -euo pipefail
+
+CONTEXT="${1:-staged}"
+files="$(bin/lefthook/get-changed-files "$CONTEXT" '\.(rb|rake|ru)$')"
+
+if [ -z "$files" ]; then
+  echo "✅ No Ruby files to lint"
+  exit 0
+fi
+
+if [ "$CONTEXT" = "all-changed" ]; then
+  echo "🔍 RuboCop on all changed Ruby files:"
+else
+  echo "🔍 RuboCop on $CONTEXT Ruby files:"
+fi
+printf "  %s\n" $files
+
+if ! bundle exec rubocop --force-exclusion --display-cop-names -- $files; then
+  echo ""
+  echo "❌ RuboCop check failed!"
+  echo "💡 Auto-fix: bundle exec rubocop --auto-correct --force-exclusion -- $files"
+  echo "🚫 Skip hook: git commit --no-verify"
+  exit 1
+fi
+echo "✅ RuboCop checks passed for Ruby files"