Add pre-commit hook for pyflakes

Add hook for pyflakes. Disable by default, as flake8 includes pyflakes.

Change-Id: I45e22e5f24f5955e8cec63c3f8c6252b4855648f
Reviewed-on: http://gerrit.causes.com/47096
Tested-by: jenkins <jenkins@brigade.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>

Author: jawshooah

config/default.yml

@@ -212,6 +212,13 @@ PreCommit:
       - '**/*.rb'
       - '**/*.rake'
 
+  Pyflakes:
+    enabled: false
+    description: 'Analyzing with pyflakes'
+    required_executable: 'pyflakes'
+    install_command: 'pip install pyflakes'
+    include: '**/*.py'
+
   PythonFlake8:
     description: 'Analyzing with flake8'
     required_executable: 'flake8'

lib/overcommit/hook/pre_commit/pyflakes.rb

@@ -0,0 +1,28 @@
+module Overcommit::Hook::PreCommit
+  # Runs `pyflakes` against any modified Python files.
+  class Pyflakes < Base
+    MESSAGE_REGEX = /^(?<file>[^:]+):(?<line>\d+):/
+
+    def run
+      result = execute(command + applicable_files)
+      return :pass if result.success?
+
+      errors = get_messages(result.stderr, :error)
+      warnings = get_messages(result.stdout, :warning)
+
+      errors + warnings
+    end
+
+    private
+
+    def get_messages(output, type)
+      # example message:
+      #   path/to/file.py:57: local variable 'x' is assigned to but never used
+      extract_messages(
+        output.split("\n").grep(MESSAGE_REGEX),
+        MESSAGE_REGEX,
+        proc { type }
+      )
+    end
+  end
+end

spec/overcommit/hook/pre_commit/pyflakes_spec.rb

@@ -0,0 +1,54 @@
+require 'spec_helper'
+
+describe Overcommit::Hook::PreCommit::Pyflakes 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.py file2.py])
+  end
+
+  context 'when pyflakes exits successfully' do
+    before do
+      result = double('result')
+      result.stub(:success? => true)
+      subject.stub(:execute).and_return(result)
+    end
+
+    it { should pass }
+  end
+
+  context 'when pyflakes exits unsucessfully' do
+    let(:result) { double('result') }
+
+    before do
+      result.stub(success?: false, stdout: '', stderr: '')
+      subject.stub(:execute).and_return(result)
+    end
+
+    context 'and it reports a warning' do
+      before do
+        result.stub(:stdout).and_return([
+          "file1.py:1: local variable 'x' is assigned to but never used"
+        ].join("\n"))
+
+        subject.stub(:modified_lines_in_file).and_return([2, 3])
+      end
+
+      it { should warn }
+    end
+
+    context 'and it reports an error' do
+      before do
+        result.stub(:stderr).and_return([
+          'file1.py:1:1: invalid syntax'
+        ].join("\n"))
+
+        subject.stub(:modified_lines_in_file).and_return([1, 2])
+      end
+
+      it { should fail_hook }
+    end
+  end
+end