[FEATURE] New pre-commit hook: Sorbet (Issue #825) (#826)

## Introduction
This pre-commit hook runs the Sorbet type-checker.
[More information about Sorbet here](https://sorbet.org/docs/overview)

Fixes #825 

## Requirements
[Sorbet](https://github.com/sorbet/sorbet)

Notes: not sure if this should be a pre-commit hook or pre-push hook to
be honest.

Co-authored-by: Shane da Silva <shane@dasilva.io>

Author: fulf

README.md

@@ -17,34 +17,43 @@ are stored in source control. You can also easily
 [add your existing hook scripts](#adding-existing-git-hooks) without writing
 any Ruby code.
 
-* [Requirements](#requirements)
-  * [Dependencies](#dependencies)
-* [Installation](#installation)
-  * [Automatically Install Overcommit Hooks](#automatically-install-overcommit-hooks)
-* [Usage](#usage)
-* [Continuous Integration](#continuous-integration)
-* [Configuration](#configuration)
-  * [Hook Options](#hook-options)
-  * [Hook Categories](#hook-categories)
-  * [Gemfile](#gemfile)
-  * [Plugin Directory](#plugin-directory)
-  * [Signature Verification](#signature-verification)
-* [Built-In Hooks](#built-in-hooks)
-  * [CommitMsg](#commitmsg)
-  * [PostCheckout](#postcheckout)
-  * [PostCommit](#postcommit)
-  * [PostMerge](#postmerge)
-  * [PostRewrite](#postrewrite)
-  * [PreCommit](#precommit)
-  * [PrePush](#prepush)
-  * [PreRebase](#prerebase)
-* [Repo-Specific Hooks](#repo-specific-hooks)
-  * [Adding Existing Git Hooks](#adding-existing-git-hooks)
-* [Security](#security)
-* [Contributing](#contributing)
-* [Community](#community)
-* [Changelog](#changelog)
-* [License](#license)
+- [Requirements](#requirements)
+  - [Windows](#windows)
+  - [Dependencies](#dependencies)
+- [Installation](#installation)
+  - [Automatically Install Overcommit Hooks](#automatically-install-overcommit-hooks)
+- [Usage](#usage)
+  - [Skipping Hooks](#skipping-hooks)
+  - [Disabling Overcommit](#disabling-overcommit)
+  - [Disabling Colorized Output](#disabling-colorized-output)
+- [Continuous Integration](#continuous-integration)
+- [Configuration](#configuration)
+  - [Hook Options](#hook-options)
+  - [Hook Categories](#hook-categories)
+    - [The `ALL` Hook](#the-all-hook)
+  - [Gemfile](#gemfile)
+  - [Plugin Directory](#plugin-directory)
+  - [Quiet Hook Runs](#quiet-hook-runs)
+  - [Concurrency](#concurrency)
+  - [Signature Verification](#signature-verification)
+- [Built-In Hooks](#built-in-hooks)
+  - [CommitMsg](#commitmsg)
+  - [PostCheckout](#postcheckout)
+  - [PostCommit](#postcommit)
+  - [PostMerge](#postmerge)
+  - [PostRewrite](#postrewrite)
+  - [PreCommit](#precommit)
+    - [WARNING: pre-commit hooks cannot have side effects](#warning-pre-commit-hooks-cannot-have-side-effects)
+  - [PrePush](#prepush)
+  - [PreRebase](#prerebase)
+- [Repo-Specific hooks](#repo-specific-hooks)
+  - [Adding Existing Git Hooks](#adding-existing-git-hooks)
+- [Security](#security)
+  - [Disabling Signature Checking](#disabling-signature-checking)
+- [Contributing](#contributing)
+- [Community](#community)
+- [Changelog](#changelog)
+- [License](#license)
 
 ## Requirements
 
@@ -561,6 +570,7 @@ issue](https://github.com/sds/overcommit/issues/238) for more details.
 * [SemiStandard](lib/overcommit/hook/pre_commit/semi_standard.rb)
 * [ShellCheck](lib/overcommit/hook/pre_commit/shell_check.rb)
 * [SlimLint](lib/overcommit/hook/pre_commit/slim_lint.rb)
+* [Sorbet](lib/overcommit/hook/pre_commit/sorbet.rb)
 * [Sqlint](lib/overcommit/hook/pre_commit/sqlint.rb)
 * [Standard](lib/overcommit/hook/pre_commit/standard.rb)
 * [Stylelint](lib/overcommit/hook/pre_commit/stylelint.rb)

config/default.yml

@@ -790,6 +790,14 @@ PreCommit:
     install_command: 'gem install slim_lint'
     include: '**/*.slim'
 
+  Sorbet:
+    enabled: false
+    description: 'Analyze with Sorbet'
+    required_executable: 'srb'
+    install_command: 'gem install sorbet'
+    command: ['srb', 'tc']
+    include: '**/*.rb'
+
   Sqlint:
     enabled: false
     description: 'Analyze with sqlint'

lib/overcommit/hook/pre_commit/sorbet.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module Overcommit::Hook::PreCommit
+  # Runs 'srb tc' against any modified files.
+  #
+  # @see https://github.com/sorbet/sorbet
+  class Sorbet < Base
+    # example of output:
+    # sorbet.rb:1: Method `foo` does not exist on `T.class_of(Bar)` https://srb.help/7003
+    MESSAGE_REGEX = /^(?<file>[^:]+):(?<line>\d+): (?<message>.*)$/.freeze
+
+    def run
+      result = execute(command, args: applicable_files)
+      return :pass if result.success?
+
+      output = result.stderr.split("\n").grep(MESSAGE_REGEX)
+
+      extract_messages(
+        output,
+        MESSAGE_REGEX
+      )
+    end
+  end
+end

spec/overcommit/hook/pre_commit/sorbet_spec.rb

@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Overcommit::Hook::PreCommit::Sorbet 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.rb file2.rb])
+  end
+
+  context 'when Sorbet exits successfully' do
+    let(:result) { double('result') }
+
+    before do
+      result.stub(:success?).and_return(true)
+      subject.stub(:execute).and_return(result)
+    end
+
+    it { should pass }
+
+    context 'and it printed a message to stderr' do
+      before do
+        result.stub(:stderr).and_return("No errors! Great job.\n")
+      end
+
+      it { should pass }
+    end
+  end
+
+  context 'when Sorbet 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(:stderr).and_return(normalize_indent(<<-MSG))
+            sorbet.rb:1: Method `foo` does not exist on `T.class_of(Bar)` https://srb.help/7003
+            5 |  foo 'bar'
+                      ^^^
+            Errors: 1
+        MSG
+      end
+
+      it { should fail_hook }
+    end
+  end
+end