Support error_code returned by specific API endpoints

lib/gitlab/error.rb

@@ -34,6 +34,17 @@ def response_message
         @response.parsed_response.message
       end
 
+      # Additional error context returned by some API endpoints
+      #
+      # @return [String]
+      def error_code
+        if @response.respond_to?(:error_code)
+          @response.error_code
+        else
+          ''
+        end
+      end
+
       private
 
       # Human friendly message.

spec/fixtures/cherry_pick_commit_failure.json

@@ -0,0 +1 @@
+{"message":"Sorry, we cannot cherry-pick this commit automatically. This commit may already have been cherry-picked, or a more recent commit may have updated some of its content.","error_code":"conflict"}

spec/gitlab/client/commits_spec.rb

@@ -65,20 +65,32 @@
   end
 
   describe '.cherry_pick_commit' do
-    before do
-      stub_post('/projects/3/repository/commits/6104942438c14ec7bd21c6cd5bd995272b3faff6/cherry_pick', 'project_commit').with(body: { branch: 'master' })
-      @cherry_pick_commit = Gitlab.cherry_pick_commit(3, '6104942438c14ec7bd21c6cd5bd995272b3faff6', 'master')
-    end
-
-    it 'gets the correct resource' do
-      expect(a_post('/projects/3/repository/commits/6104942438c14ec7bd21c6cd5bd995272b3faff6/cherry_pick')
-        .with(body: { branch: 'master' }))
-        .to have_been_made
-    end
-
-    it 'returns the correct response' do
-      expect(@cherry_pick_commit).to be_a Gitlab::ObjectifiedHash
-      expect(@cherry_pick_commit.id).to eq('6104942438c14ec7bd21c6cd5bd995272b3faff6')
+    context 'on success' do
+      before do
+        stub_post('/projects/3/repository/commits/6104942438c14ec7bd21c6cd5bd995272b3faff6/cherry_pick', 'project_commit').with(body: { branch: 'master' })
+        @cherry_pick_commit = Gitlab.cherry_pick_commit(3, '6104942438c14ec7bd21c6cd5bd995272b3faff6', 'master')
+      end
+
+      it 'gets the correct resource' do
+        expect(a_post('/projects/3/repository/commits/6104942438c14ec7bd21c6cd5bd995272b3faff6/cherry_pick')
+          .with(body: { branch: 'master' }))
+          .to have_been_made
+      end
+
+      it 'returns the correct response' do
+        expect(@cherry_pick_commit).to be_a Gitlab::ObjectifiedHash
+        expect(@cherry_pick_commit.id).to eq('6104942438c14ec7bd21c6cd5bd995272b3faff6')
+      end
+    end
+
+    context 'on failure' do
+      it 'includes the error_code' do
+        stub_post('/projects/3/repository/commits/6104942438c14ec7bd21c6cd5bd995272b3faff6/cherry_pick', 'cherry_pick_commit_failure', 400)
+
+        expect { Gitlab.cherry_pick_commit(3, '6104942438c14ec7bd21c6cd5bd995272b3faff6', 'master') }.to raise_error(Gitlab::Error::BadRequest) do |ex|
+          expect(ex.error_code).to eq('conflict')
+        end
+      end
     end
   end
 

spec/gitlab/error_spec.rb

@@ -68,4 +68,39 @@
       expect(described_class.new(response_double).send(:build_error_message)).to match(/Retry text/)
     end
   end
+
+  describe '#error_code' do
+    it 'returns the value when available' do
+      headers = { 'content-type' => 'application/json' }
+      response_double = double(
+        'response',
+        body: 'Retry later',
+        to_s: 'Retry text',
+        parsed_response: { message: 'Retry hash' },
+        code: 400,
+        error_code: 'conflict',
+        options: {},
+        headers: headers,
+        request: @request_double
+      )
+
+      expect(described_class.new(response_double).error_code).to eq 'conflict'
+    end
+
+    it 'returns nothing when unavailable' do
+      headers = { 'content-type' => 'application/json' }
+      response_double = double(
+        'response',
+        body: 'Retry later',
+        to_s: 'Retry text',
+        parsed_response: { message: 'Retry hash' },
+        code: 400,
+        options: {},
+        headers: headers,
+        request: @request_double
+      )
+
+      expect(described_class.new(response_double).error_code).to eq ''
+    end
+  end
 end