Support stylelint 16+, which emits messages on stderr

lib/overcommit/hook/pre_commit/stylelint.rb

@@ -12,7 +12,7 @@ class Stylelint < Base
 
     def run
       result = execute(command, args: applicable_files)
-      output = result.stdout.chomp
+      output = result.stdout + result.stderr.chomp
       return :pass if result.success? && output.empty?
 
       extract_messages(

spec/overcommit/hook/pre_commit/stylelint_spec.rb

@@ -15,14 +15,15 @@
     before do
       result = double('result')
       result.stub(:success?).and_return(true)
+      result.stub(:stderr).and_return('')
       result.stub(:stdout).and_return('')
       subject.stub(:execute).and_return(result)
     end
 
     it { should pass }
   end
 
-  context 'when stylelint exits unsucessfully' do
+  context 'when stylelint exits unsucessfully with messages on stdout (stylelint < 16)' do
     let(:result) { double('result') }
 
     before do
@@ -32,6 +33,7 @@
     context 'and it reports an error' do
       before do
         result.stub(:success?).and_return(false)
+        result.stub(:stderr).and_return('')
         result.stub(:stdout).and_return([
           'index.css: line 4, col 4, error - Expected indentation of 2 spaces (indentation)',
           'form.css: line 10, col 6, error - Expected indentation of 4 spaces (indentation)',
@@ -45,4 +47,29 @@
       end
     end
   end
+
+  context 'when stylelint exits unsucessfully with messages on stderr (stylelint >= 16)' do
+    let(:result) { double('result') }
+
+    before do
+      subject.stub(:execute).and_return(result)
+    end
+
+    context 'and it reports an error' do
+      before do
+        result.stub(:success?).and_return(false)
+        result.stub(:stdout).and_return('')
+        result.stub(:stderr).and_return([
+          'index.css: line 4, col 4, error - Expected indentation of 2 spaces (indentation)',
+          'form.css: line 10, col 6, error - Expected indentation of 4 spaces (indentation)',
+        ].join("\n"))
+      end
+
+      it { should fail_hook }
+
+      it 'extracts lines numbers correctly from output' do
+        expect(subject.run.map(&:line)).to eq([4, 10])
+      end
+    end
+  end
 end