如何在RoR项目中使用policial gem？求实例化detective的相关指导

Hey there! I get it, the official Policial docs are pretty high-level—let’s break this down with concrete examples so you can start checking PRs for style guide violations right away.

Step 1: Install the Gem #

First, add Policial and your preferred style guide (most folks use RuboCop) to your Rails project’s Gemfile:

gem 'policial'
gem 'rubocop' # Required for Ruby style checks

Run bundle install to get everything set up.

Step 2: Instantiate the Detective (The Core Part You’re Asking About) #

The detective can be instantiated wherever you need to run PR checks—this could be a standalone script, a rake task, or even a CI workflow. Let’s start with a local test script, then move to GitHub PR integration.

Example 1: Local File Check (Test Things Out) #

Create a script like script/check_style.rb to test Policial on a single file:

require 'policial'
require 'rails' # Skip if not in a Rails project

# Initialize the detective with your style guide(s)
detective = Policial::Detective.new(
  style_guides: [Policial::StyleGuides::RuboCop.new]
)

# Point to your project root
repo_path = Rails.root.to_s || './'

# Pick a file to check
file_path = 'app/models/user.rb'
file_content = File.read(file_path)

# Wrap the file in Policial's File object
policial_file = Policial::File.new(file_path, file_content, repo_path)

# Run the check
violations = detective.check(policial_file)

# Print results
if violations.empty?
  puts "No style violations found in #{file_path}!"
else
  puts "⚠️ Violations in #{file_path}:"
  violations.each do |violation|
    puts "- Line #{violation.line}: #{violation.message} (Rule: #{violation.rule_id})"
  end
end

Run it with bundle exec ruby script/check_style.rb to see results immediately.

Example 2: Check a GitHub Pull Request #

To check actual PRs, you’ll need to fetch changed files from the GitHub API. Here’s how to do that in a script:

require 'policial'
require 'octokit'
require 'base64'

# Initialize GitHub client (use a personal access token or GitHub Actions token)
github_client = Octokit::Client.new(access_token: ENV['GITHUB_TOKEN'])
repo_name = 'your-username/your-rails-repo'
pr_number = ENV['PR_NUMBER'].to_i # Pass this via environment variable

# Initialize the detective
detective = Policial::Detective.new(
  style_guides: [Policial::StyleGuides::RuboCop.new]
)
repo_path = Rails.root.to_s

# Fetch PR details and changed files
pr = github_client.pull_request(repo_name, pr_number)
changed_files = github_client.pull_request_files(repo_name, pr_number)

# Check each Ruby file in the PR
changed_files.each do |file|
  next unless file.filename.end_with?('.rb') # Only check Ruby files

  # Get the file content from the PR's head branch
  content = github_client.contents(repo_name, path: file.filename, ref: pr.head.sha).content
  decoded_content = Base64.decode64(content)

  # Run style check
  policial_file = Policial::File.new(file.filename, decoded_content, repo_path)
  violations = detective.check(policial_file)

  # Output results
  unless violations.empty?
    puts "\n📝 Violations in #{file.filename}:"
    violations.each { |v| puts "  Line #{v.line}: #{v.message}" }
  end
end

You can run this locally by setting GITHUB_TOKEN and PR_NUMBER in your terminal, or integrate it into GitHub Actions (see below).

Step 3: Automate with GitHub Actions #

To run this check automatically on every PR, create a workflow file at .github/workflows/style_check.yml:

name: PR Style Check
on: [pull_request]

jobs:
  style-check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Set up Ruby
        uses: ruby/setup-ruby@v1
        with:
          ruby-version: '3.2' # Match your project's Ruby version
          bundler-cache: true
      - name: Run Policial check
        run: bundle exec ruby script/check_pr_style.rb
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          PR_NUMBER: ${{ github.event.pull_request.number }}

This will run your script on every PR and report style violations in the workflow logs.

Key Tips #

• Custom Style Guides: If you use a custom RuboCop config, Policial will automatically pick up your .rubocop.yml file in the repo root.
• Error Handling: Add checks for missing files or API errors to make your script more robust.
• Other Style Guides: Policial supports other guides too (like HamlLint)—just replace Policial::StyleGuides::RuboCop.new with the appropriate class.

Content of the question comes from Stack Exchange, asked by hermes agm