Added RuboCop linter

Test Plan:
Add the following JSON to your `.arclint`:

```lang=json
"rubocop": {
  "type": "rubocop",
  "include": "(\\.rb$)"
}
```

Then, add a ruby file with errors, for instance:

```lang=ruby
def hello()
  puts 'world'
end
```

Run `arc lint`. It should come up with something along the line of: "Omit the parentheses in defs when the method doesn't accept any arguments."

Reviewers: joshuaspence, remon, #blessed_reviewers, epriestley

Reviewed By: joshuaspence, #blessed_reviewers, epriestley

Subscribers: reu, calfzhou, jjooss, cburroughs, chad, Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D10738

src/__phutil_library_map__.php

@@ -161,6 +161,8 @@ phutil_register_library_map(array(
     'ArcanistRepositoryAPIMiscTestCase' => 'repository/api/__tests__/ArcanistRepositoryAPIMiscTestCase.php',
     'ArcanistRepositoryAPIStateTestCase' => 'repository/api/__tests__/ArcanistRepositoryAPIStateTestCase.php',
     'ArcanistRevertWorkflow' => 'workflow/ArcanistRevertWorkflow.php',
+    'ArcanistRuboCopLinter' => 'lint/linter/ArcanistRuboCopLinter.php',
+    'ArcanistRuboCopLinterTestCase' => 'lint/linter/__tests__/ArcanistRuboCopLinterTestCase.php',
     'ArcanistRubyLinter' => 'lint/linter/ArcanistRubyLinter.php',
     'ArcanistRubyLinterTestCase' => 'lint/linter/__tests__/ArcanistRubyLinterTestCase.php',
     'ArcanistScriptAndRegexLinter' => 'lint/linter/ArcanistScriptAndRegexLinter.php',
@@ -347,6 +349,8 @@ phutil_register_library_map(array(
     'ArcanistRepositoryAPIMiscTestCase' => 'ArcanistTestCase',
     'ArcanistRepositoryAPIStateTestCase' => 'ArcanistTestCase',
     'ArcanistRevertWorkflow' => 'ArcanistWorkflow',
+    'ArcanistRuboCopLinter' => 'ArcanistExternalLinter',
+    'ArcanistRuboCopLinterTestCase' => 'ArcanistExternalLinterTestCase',
     'ArcanistRubyLinter' => 'ArcanistExternalLinter',
     'ArcanistRubyLinterTestCase' => 'ArcanistExternalLinterTestCase',
     'ArcanistScriptAndRegexLinter' => 'ArcanistLinter',

src/lint/linter/ArcanistRuboCopLinter.php

@@ -0,0 +1,120 @@
+<?php
+
+final class ArcanistRuboCopLinter extends ArcanistExternalLinter {
+
+  private $config;
+
+  public function getInfoName() {
+    return 'RuboCop';
+  }
+
+  public function getInfoURI() {
+    return 'http://batsov.com/rubocop';
+  }
+
+  public function getInfoDescription() {
+    return pht(
+      'RuboCop is a Ruby static code analyzer, based on the community Ruby '.
+      'style guide.');
+  }
+
+  public function getLinterName() {
+    return 'RuboCop';
+  }
+
+  public function getLinterConfigurationName() {
+    return 'rubocop';
+  }
+
+  public function getDefaultBinary() {
+    return 'rubocop';
+  }
+
+  public function getVersion() {
+    list($stdout) = execx('%C --version', $this->getExecutableCommand());
+
+    $matches = array();
+    if (preg_match('/^(?P<version>\d+\.\d+\.\d+)$/', $stdout, $matches)) {
+      return $matches['version'];
+    } else {
+      return false;
+    }
+  }
+
+  public function getInstallInstructions() {
+    return pht('Install RuboCop using `%s`.', 'gem install rubocop');
+  }
+
+  protected function getMandatoryFlags() {
+    $options = array(
+      '--format=json',
+    );
+
+    if ($this->config) {
+      $options[] = '--config='.$this->config;
+    }
+
+    return $options;
+  }
+
+  public function getLinterConfigurationOptions() {
+    $options = array(
+      'rubocop.config' => array(
+        'type' => 'optional string',
+        'help' => pht('A custom configuration file.'),
+      ),
+    );
+
+    return $options + parent::getLinterConfigurationOptions();
+  }
+
+  public function setLinterConfigurationValue($key, $value) {
+    switch ($key) {
+      case 'rubocop.config':
+        $this->config = $value;
+        return;
+    }
+
+    return parent::setLinterConfigurationValue($key, $value);
+  }
+
+  protected function parseLinterOutput($path, $err, $stdout, $stderr) {
+    $results = phutil_json_decode($stdout);
+    $messages = array();
+
+    foreach ($results['files'] as $file) {
+      foreach ($file['offenses'] as $offense) {
+        $message = id(new ArcanistLintMessage())
+          ->setPath($file['path'])
+          ->setDescription($offense['message'])
+          ->setLine($offense['location']['line'])
+          ->setChar($offense['location']['column'])
+          ->setSeverity($this->getLintMessageSeverity($offense['severity']))
+          ->setName($this->getLinterName())
+          ->setCode($offense['cop_name']);
+        $messages[] = $message;
+      }
+    }
+
+    return $messages;
+  }
+
+  /*
+    Take the string from RuboCop's severity terminology and return an
+    ArcanistLintSeverity
+   */
+  protected function getDefaultMessageSeverity($code) {
+    switch ($code) {
+      case 'convention':
+      case 'refactor':
+      case 'warning':
+        return ArcanistLintSeverity::SEVERITY_WARNING;
+      case 'error':
+      case 'fatal':
+        return ArcanistLintSeverity::SEVERITY_ERROR;
+      default:
+        return ArcanistLintSeverity::SEVERITY_ADVICE;
+    }
+  }
+
+}

src/lint/linter/__tests__/ArcanistRuboCopLinterTestCase.php

@@ -0,0 +1,10 @@
+<?php
+
+final class ArcanistRuboCopLinterTestCase
+  extends ArcanistExternalLinterTestCase {
+
+  public function testLinter() {
+    $this->executeTestsInDirectory(dirname(__FILE__).'/rubocop/');
+  }
+
+}

src/lint/linter/__tests__/rubocop/convention.lint-test

@@ -0,0 +1,4 @@
+def hello()
+end
+~~~~~~~~~~
+warning:1:10

src/lint/linter/__tests__/rubocop/error.lint-test

@@ -0,0 +1,4 @@
+def hello
+  puts 'world'
+~~~~~~~~~~
+error:3:1

src/lint/linter/__tests__/rubocop/no_errors.lint-test

@@ -0,0 +1,4 @@
+def hello
+  puts 'hello world'
+end
+~~~~~~~~~~

src/lint/linter/__tests__/rubocop/warning.lint-test

@@ -0,0 +1,5 @@
+def hello(unused)
+  puts 'hi'
+end
+~~~~~~~~~
+warning:1:11