Add Dogma pre-commit hook to check Elixir source files

Dogma is a code style linter for Elixir language.
Dogma's source code is available at https://github.com/lpil/dogma
This pre-commit hook executes dogma and reports errors.

Author: dtengeri

config/default.yml

@@ -188,6 +188,14 @@ PreCommit:
     install_command: 'npm install -g csslint'
     include: '**/*.css'
 
+  Dogma:
+    enabled: false
+    description: 'Analyzing with dogma'
+    required_executable: 'mix'
+    include:
+      - '**/*.ex'
+      - '**/*.exs'
+
   EsLint:
     enabled: false
     description: 'Analyzing with ESLint'

lib/overcommit/hook/pre_commit/dogma.rb

@@ -0,0 +1,31 @@
+module Overcommit::Hook::PreCommit
+  # Runs `dogma` against any modified ex files.
+  #
+  # @see http://eslint.org/
+  class Dogma < Base
+    def run
+      result = execute command
+      return :pass if result.success?
+
+      messages = []
+      # example message:
+      #  == web/channels/user_socket.ex ==
+      #  26: LineLength: Line length should not exceed 80 chars (was 83).
+      #  1: ModuleDoc: Module Sample.UserSocket is missing a @moduledoc.
+      output = result.stdout.chomp.match(/(==.+)/m)
+
+      if output
+        output.captures.first.split(/\n\n/).each do |error_group|
+          errors = error_group.split /\n/
+          file = errors.shift.gsub /[ =]/, ''
+          errors.each do |error|
+            line = error.split(': ').first
+            messages << Overcommit::Hook::Message.new(:error, file, line, "#{file}: #{error}")
+          end
+        end
+      end
+
+      messages
+    end
+  end
+end

spec/overcommit/hook/pre_commit/dogma_spec.rb

@@ -0,0 +1,49 @@
+require 'spec_helper'
+
+describe Overcommit::Hook::PreCommit::Dogma do
+  let(:config)  { Overcommit::ConfigurationLoader.default_configuration }
+  let(:context) { double('context') }
+  subject { described_class.new(config, context) }
+
+  before do
+    subject.stub(:applicable_files).and_return(%w[file1.ex file2.exs])
+  end
+
+  context 'when dogma exits successfully' do
+    before do
+      result = double('result')
+      result.stub(:success?).and_return(true)
+      subject.stub(:execute).and_return(result)
+    end
+
+    it { should pass }
+  end
+
+  context 'when dogma exits unsucessfully' do
+    let(:result) { double('result') }
+
+    before do
+      result.stub(:success?).and_return(false)
+      subject.stub(:execute).and_return(result)
+    end
+
+    context 'and it reports an error' do
+      before do
+        result.stub(:stdout).and_return([
+          '27 files, 3 errors!',
+          '',
+          '== test/support/model_case.ex ==',
+          '47: LineLength: Line length should not exceed 80 chars (was 85).',
+          '',
+          '== test/test_helper.exs ==',
+          '6: TrailingBlankLines: Blank lines detected at end of file',
+          '5: TrailingWhitespace: Trailing whitespace detected',
+          '',
+        ].join("\n"))
+        result.stub(:stderr).and_return('')
+      end
+
+      it { should fail_hook }
+    end
+  end
+end