Precommit Command

Executes the production-ready precommit workflow to ensure code quality before commits.

What It Does

Runs four quality checks in sequence:

1. Compilation with warnings as errors
2. Code formatting with Styler
3. Static analysis with Credo
4. Test suite execution

Usage

/precommit          # Run all checks
/precommit --fix    # Run checks and auto-fix formatting issues

Implementation

Step 1: Check Dependencies

First verify that required tools are installed:

# Check if credo is in mix.exs
if ! grep -q ':credo' mix.exs; then
  echo "❌ Missing dependency: credo"
  echo "Add to mix.exs:"
  echo '  {:credo, "~> 1.7", only: [:dev, :test], runtime: false}'
  exit 1
fi

# Check if styler is in mix.exs
if ! grep -q ':styler' mix.exs; then
  echo "❌ Missing dependency: styler"
  echo "Add to mix.exs:"
  echo '  {:styler, "~> 1.0", only: [:dev, :test], runtime: false}'
  exit 1
fi

# Check if styler is configured in .formatter.exs
if [[ -f ".formatter.exs" ]]; then
  if ! grep -q 'Styler' .formatter.exs; then
    echo "⚠️  Styler not configured in .formatter.exs"
    echo "Add: plugins: [Styler]"
  fi
fi

Step 2: Run Checks

Execute each check in order:

echo "🔍 Running precommit checks..."
echo ""

# 1. Compile with warnings as errors
echo "1/4 Compiling..."
if mix compile --warnings-as-errors; then
  echo "✅ Compilation passed"
else
  echo "❌ Compilation failed with warnings"
  exit 1
fi

echo ""

# 2. Format code (with --fix flag) or check formatting
echo "2/4 Formatting..."
if [[ "$1" == "--fix" ]]; then
  mix format
  echo "✅ Code formatted"
else
  if mix format --check-formatted 2>&1 | grep -q "mix format"; then
    echo "❌ Code needs formatting. Run: mix format"
    exit 1
  else
    echo "✅ Formatting correct"
  fi
fi

echo ""

# 3. Run credo
echo "3/4 Static analysis..."
if mix credo --strict; then
  echo "✅ Credo passed"
else
  echo "❌ Credo found issues"
  exit 1
fi

echo ""

# 4. Run tests
echo "4/4 Running tests..."
if mix test; then
  echo "✅ All tests passed"
else
  echo "❌ Tests failed"
  exit 1
fi

echo ""
echo "✅ All precommit checks passed!"

Step 3: Report Results

If all checks pass:

✅ Precommit Checks Complete

All checks passed:
✅ Compilation (0 warnings)
✅ Formatting (all files formatted)
✅ Credo (strict mode)
✅ Tests (X tests, 0 failures)

Ready to commit!

If any check fails:

❌ Precommit Checks Failed

Results:
✅ Compilation
❌ Formatting - 3 files need formatting
  Run: mix format

Next steps:
1. Run: mix format
2. Review changes
3. Run /precommit again

Auto-Fix Mode

With --fix flag:

🔧 Precommit with Auto-Fix

1/4 Compilation... ✅
2/4 Formatting... 🔧 Fixed 3 files
3/4 Static analysis... ✅
4/4 Tests... ✅

Auto-fixed:
- Formatted 3 files
- Run git diff to review changes

✅ All checks passed!

Error Handling

Missing Dependencies

❌ Required dependencies not found

Missing:
- credo: Add {:credo, "~> 1.7", only: [:dev, :test], runtime: false}
- styler: Add {:styler, "~> 1.0", only: [:dev, :test], runtime: false}

After adding to mix.exs, run:
mix deps.get

Compilation Errors

❌ Compilation Failed

Errors found:
  lib/my_app/accounts.ex:42: warning: variable "user" is unused

Fix:
- Remove unused variables or prefix with underscore: _user
- Address all warnings

Run: mix compile --warnings-as-errors

Test Failures

❌ Tests Failed

Failed tests:
  1) test create_user/1 creates user (MyApp.AccountsTest)
     test/my_app/accounts_test.exs:42
     Assertion with == failed
     left:  "Alice"
     right: "Bob"

Fix:
- Review test failure details above
- Fix implementation or update tests
- Run: mix test test/my_app/accounts_test.exs:42

Configuration

Create .precommit.exs in project root to customize (optional):

[
  checks: [
    compile: true,
    format: true,
    credo: true,
    test: true
  ],
  # Skip specific checks (not recommended)
  skip: []
]

Integration with Git Hooks

To run automatically before each commit, add to .git/hooks/pre-commit:

#!/bin/bash
set -e

echo "Running precommit checks..."
claude-code /precommit

if [ $? -ne 0 ]; then
  echo ""
  echo "Precommit checks failed. Commit aborted."
  echo "Fix issues and try again, or use --no-verify to skip (not recommended)."
  exit 1
fi

Make executable:

chmod +x .git/hooks/pre-commit

Tips

1. Run frequently: Don't wait until commit time
2. Fix as you go: Address warnings immediately
3. Use --fix: Auto-fix formatting issues
4. Focus on tests first: If tests fail, fix before other checks
5. Batch formatting: Run mix format on entire codebase periodically

Success Criteria

Precommit succeeds when:

• ✅ All code compiles without warnings
• ✅ All files properly formatted
• ✅ Credo passes in strict mode
• ✅ All tests pass
• ✅ No flaky tests (consistent pass/fail)

Related Commands

• /review - Comprehensive code review beyond precommit checks
• /spike - Fast prototyping mode (skips some checks)
• /spike-migrate - Upgrade SPIKE code to pass precommit