add ConstraintError class + small rubocop refactor

lib/neo4j-server/cypher_response.rb

@@ -13,6 +13,7 @@ def initialize(msg, status, code)
         end
       end
 
+      class ConstraintError < ResponseError; end
 
       class HashEnumeration
         include Enumerable
@@ -201,9 +202,15 @@ def set_error(error)
         self
       end
 
+      CONSTRAINT_ERROR = 'Neo.ClientError.Schema.ConstraintViolation'
       def raise_error
         fail 'Tried to raise error without an error' unless @error
-        fail ResponseError.new(@error_msg, @error_status, @error_code)
+        error_class = constraint_error? ? ConstraintError : ResponseError
+        fail error_class.new(@error_msg, @error_status, @error_code)
+      end
+
+      def constraint_error?
+        @error_code == CONSTRAINT_ERROR || @error_msg.include?('already exists with')
       end
 
       def raise_cypher_error
@@ -228,11 +235,7 @@ def self.create_with_tx(response)
 
         new(response, true).tap do |cr|
           body = response.body
-          if body[:errors].empty?
-            cr.set_data(body[:results].first)
-          else
-            cr.set_error(body[:errors].first)
-          end
+          body[:errors].empty? ? cr.set_data(body[:results].first) : cr.set_error(body[:errors].first)
         end
       end
 

spec/neo4j-server/unit/cypher_response_unit_spec.rb

@@ -213,6 +213,12 @@ def successful_response(response)
           it { is_expected.to be_truthy }
         end
       end
+
+      describe 'CypherResponse::ConstraintError' do
+        it 'inherits from ResponseError' do
+          expect(CypherResponse::ConstraintError.new(nil, nil, nil)).to be_a(CypherResponse::ResponseError)
+        end
+      end
     end
   end
 end

spec/shared_examples/label.rb

@@ -230,6 +230,28 @@
     end
   end
 
+  describe 'unsatisfied constraint' do
+    let(:label) { Neo4j::Label.create(:MyFoo) }
+    before do
+      if Neo4j::Transaction.current
+        Neo4j::Transaction.current.failure
+        Neo4j::Transaction.current.close
+      end
+      Neo4j::Session.current.query.match('(n:MyFoo)').delete(:n).exec
+      label.create_constraint(:bar, type: :unique)
+    end
+
+    after do
+      label.drop_constraint(:bar, type: :unique)
+      Neo4j::Session.current.query.match('(n:MyFoo)').delete(:n).exec
+    end
+
+    it 'raises a ConstraintError' do
+      expect { Neo4j::Node.create({bar: 'dawn'}, :MyFoo) }.not_to raise_error
+      expect { Neo4j::Node.create({bar: 'dawn'}, :MyFoo) }.to raise_error { Neo4j::Server::CypherResponse::ConstraintError }
+    end
+  end
+
   describe 'instance methods' do
     describe 'create_index' do
       it 'creates an index on given properties' do