Add support for go fmt #687

config/default.yml

@@ -337,6 +337,14 @@ PreCommit:
     flags: ['-IEHnw']
     keywords: ['FContext','FDescribe','FIt','FMeasure','FSpecify','FWhen']
 
+  GoFmt:
+    enabled: true
+    description: 'Fix with go fmt'
+    required_executable: 'go'
+    command: ['go', 'fmt']
+    parallelize: false
+    include: '**/*.go'
+
   GoLint:
     enabled: false
     description: 'Analyze with golint'

lib/overcommit/hook/pre_commit/go_fmt.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module Overcommit::Hook::PreCommit
+  # Runs go fmt for all modified Go files
+  class GoFmt < Base
+    def run
+      errors = []
+      applicable_files.each do |file|
+        result = execute(command, args: [file])
+        errors << (result.stdout + result.stderr) unless result.success?
+      end
+      return :pass if errors.empty?
+
+      [:fail, errors.join("\n")]
+    end
+  end
+end

spec/overcommit/hook/pre_commit/go_fmt_spec.rb

@@ -0,0 +1,99 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Overcommit::Hook::PreCommit::GoFmt do
+  let(:config)  { Overcommit::ConfigurationLoader.default_configuration }
+  let(:context) { double('context') }
+  subject { described_class.new(config, context) }
+
+  let(:files) do
+    %w[
+      pkg1/file1.go
+      pkg1/file2.go
+      pkg2/file1.go
+      file1.go
+    ]
+  end
+  before do
+    subject.stub(:applicable_files).and_return(files)
+  end
+
+  context 'when go fmt exits successfully' do
+    let(:result) { double('result') }
+
+    before do
+      result.stub(success?: true, stderr: '', stdout: '')
+      subject.stub(:execute).and_return(result)
+    end
+
+    it 'executes go fmt for each file' do
+      files.each do |file|
+        expect(subject).to receive(:execute).with(subject.command, args: [file]).once
+      end
+      subject.run
+    end
+
+    it 'passes' do
+      expect(subject).to pass
+    end
+  end
+
+  context 'when go fmt exits unsucessfully' do
+    let(:result) { double('result') }
+
+    before do
+      result.stub(:success?).and_return(false)
+      subject.stub(:execute).and_return(result)
+    end
+
+    context 'when go fmt returns an error to stdout' do
+      let(:error_message) { 'some go fmt error' }
+
+      before do
+        result.stub(:stdout).and_return(error_message)
+        result.stub(:stderr).and_return('')
+      end
+
+      it 'executes go fmt for each file' do
+        files.each do |file|
+          expect(subject).to receive(:execute).with(subject.command, args: [file]).once
+        end
+        subject.run
+      end
+
+      it 'fails' do
+        expect(subject).to fail_hook
+      end
+
+      it 'returns errors' do
+        message = subject.run.last
+        expect(message).to eq Array.new(files.count, error_message).join("\n")
+      end
+    end
+
+    context 'when fo fmt returns an error to stderr' do
+      let(:error_message) { 'go: command not found' }
+      before do
+        result.stub(:stdout).and_return('')
+        result.stub(:stderr).and_return(error_message)
+      end
+
+      it 'executes go fmt for each file' do
+        files.each do |file|
+          expect(subject).to receive(:execute).with(subject.command, args: [file]).once
+        end
+        subject.run
+      end
+
+      it 'fails' do
+        expect(subject).to fail_hook
+      end
+
+      it 'returns valid message' do
+        message = subject.run.last
+        expect(message).to eq Array.new(files.count, error_message).join("\n")
+      end
+    end
+  end
+end