Pre-commit hook - Validate Syntax for Ruby files

pre-commit

#!/usr/bin/env ruby

=begin

A hook to make sure that all staged .rb files are syntatically correct.
The hook tries to run `ruby -c file_path` for all those files and
prints outs the errors if any and halts the commit.

If you want to use this pre-commit, simply copy the code and create a
file called 'pre-commit' inside your .git/hooks directory.

Ensure to make file executable as well `chmod +x .git/hooks/pre-commit`
=end

# SyntaxChecker validates the syntax of all files
class SyntaxChecker
  require 'open3'

  PASS_MSG = 'pre-commit - ruby syntax check passed'.freeze
  FAIL_MSG = 'pre-commit - ruby syntax check failed'.freeze

  class << self
    def perform
      staged_files = `git diff --name-only --staged`
      staged_ruby_files = staged_files.split("\n")
      pick_rb_files(staged_ruby_files)
      return if staged_ruby_files.empty?

      errors = run_syntax_check(staged_ruby_files)
      return p PASS_MSG  if errors.empty?

      p FAIL_MSG, errors and exit 1
    end

    private

    def pick_rb_files(files)
      files.select! { |f| f[-3] == '.' && f[-2] == 'r' && f[-1] == 'b' }
    end

    def run_syntax_check(files)
      errors = ''
      files.each do |file_path|
        cmd = "ruby -c #{file_path}"
        Open3.popen3(cmd) do |_in, _out, err|
          err_text = err.read.to_s
          errors += err_text unless err_text.empty?
        end
      end
      errors
    end
  end
end

SyntaxChecker.perform