Terraform support

config/default.yml

@@ -737,12 +737,19 @@ PreCommit:
     install_command: 'brew install swiftlint'
     include: '**/*.swift'
 
+  TerraformFormat:
+    enabled: false
+    description: 'Analyze with Terraform'
+    required_executable: 'terraform'
+    flags: ['fmt', '-check=true', '-diff=false']
+    include: '**/*.tf'
+
   TsLint:
-      enabled: false
-      description: 'Analyze with TSLint'
-      required_executable: 'tslint'
-      install_command: 'npm install -g tslint typescript'
-      include: '**/*.ts'
+    enabled: false
+    description: 'Analyze with TSLint'
+    required_executable: 'tslint'
+    install_command: 'npm install -g tslint typescript'
+    include: '**/*.ts'
 
   TrailingWhitespace:
     enabled: false

lib/overcommit/hook/pre_commit/terraform_format.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module Overcommit::Hook::PreCommit
+  # Runs 'terraform fmt' against any modified *.tf files.
+  #
+  # @see https://www.terraform.io/docs/commands/fmt.html
+  class TerraformFormat < Base
+    def run
+      messages = []
+      applicable_files.each do |f|
+        result = execute(command, args: [f])
+        unless result.success?
+          messages << Overcommit::Hook::Message.new(:error, f, nil, "violation found in #{f}")
+        end
+      end
+      messages
+    end
+  end
+end

spec/overcommit/hook/pre_commit/terraform_format_spec.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Overcommit::Hook::PreCommit::TerraformFormat 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.tf file2.tf])
+  end
+
+  context 'when Terraform 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 Terraform exits unsucessfully' do
+    let(:result_ok) { double('result') }
+    let(:result_bad) { double('result') }
+    let(:cmdline) { %w[terraform fmt -check=true -diff=false] }
+
+    before do
+      result_ok.stub(:success?).and_return(true)
+      result_bad.stub(:success?).and_return(false)
+      subject.stub(:execute).with(cmdline, args: ['file1.tf']).and_return(result_ok)
+      subject.stub(:execute).with(cmdline, args: ['file2.tf']).and_return(result_bad)
+    end
+
+    it { should fail_hook }
+  end
+end