ESLint pre-commit hook fails if there are problems (#475)

* Fix #458: Overcommit fails if ESLint fails for whatever reason

* Add check for bindly_pass option

* Delete extra empty line

* Return the stderr output along with exit status

* Remove bindly_pass option

Author: Dom Corvasce

lib/overcommit/hook/pre_commit/es_lint.rb

@@ -19,12 +19,15 @@ class EsLint < Base
     def run
       result = execute(command, args: applicable_files)
       output = result.stdout.chomp
+      messages = output.split("\n").grep(/Warning|Error/)
+
+      return [:fail, result.stderr] if messages.empty? && !result.success?
       return :pass if result.success? && output.empty?
 
       # example message:
       #   path/to/file.js: line 1, col 0, Error - Error message (ruleName)
       extract_messages(
-        output.split("\n").grep(/Warning|Error/),
+        messages,
         /^(?<file>(?:\w:)?[^:]+):[^\d]+(?<line>\d+).*?(?<type>Error|Warning)/,
         lambda { |type| type.downcase.to_sym }
       )

spec/overcommit/hook/pre_commit/es_lint_spec.rb

@@ -9,6 +9,20 @@
     subject.stub(:applicable_files).and_return(%w[file1.js file2.js])
   end
 
+  context 'when eslint is unable to run' do
+    let(:result) { double('result') }
+
+    before do
+      result.stub(:stderr).and_return('SyntaxError: Use of const in strict mode.')
+      result.stub(:stdout).and_return('')
+
+      result.stub(:success?).and_return(false)
+      subject.stub(:execute).and_return(result)
+    end
+
+    it { should fail_hook }
+  end
+
   context 'when eslint exits successfully' do
     let(:result) { double('result') }