Add postgresql support

activerecord-rescue_from_duplicate.gemspec

@@ -26,5 +26,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'sqlite3'
   spec.add_development_dependency 'mysql2'
   spec.add_development_dependency 'rspec'
+  spec.add_development_dependency 'pg'
   spec.add_development_dependency 'pry'
 end

lib/rescue_from_duplicate/active_record/extension.rb

@@ -45,8 +45,14 @@ def exception_validator(exception)
     protected
 
     def exception_columns(exception)
-      columns = exception.message =~ /SQLite3::ConstraintException/ ? sqlite3_exception_columns(exception) : other_exception_columns(exception)
-      columns.sort
+      columns = case
+      when exception.message =~ /SQLite3::ConstraintException/
+        sqlite3_exception_columns(exception)
+      when exception.message =~ /PG::UniqueViolation/
+        postgresql_exception_columns(exception)
+      else
+        other_exception_columns(exception)
+      end
     end
 
     def exception_rescuer(exception)
@@ -55,15 +61,23 @@ def exception_rescuer(exception)
       _rescue_from_duplicates.detect { |rescuer| rescuer.matches?(columns) }
     end
 
+    def postgresql_exception_columns(exception)
+      extract_columns(exception.message[/Key \((.*?)\)=\(.*?\) already exists./, 1])
+    end
+
     def sqlite3_exception_columns(exception)
-      columns = exception.message[/column (.*) is not unique/, 1]
-      return unless columns
-      columns.split(",").map(&:strip)
+      extract_columns(exception.message[/columns? (.*) (?:is|are) not unique/, 1])
+    end
+
+    def extract_columns(columns_string)
+      return unless columns_string
+      columns_string.split(",").map(&:strip).sort
     end
 
     def other_exception_columns(exception)
       indexes = self.class.connection.indexes(self.class.table_name)
-      indexes.detect{ |i| exception.message.include?(i.name) }.try(:columns) || []
+      columns = indexes.detect{ |i| exception.message.include?(i.name) }.try(:columns) || []
+      columns.sort
     end
 
     def rescue_with_validator?(columns, validator)

spec/rescue_from_duplicate_spec.rb

@@ -53,7 +53,7 @@
         Rescuable.stub(connection: double(indexes: []))
       }
 
-      let(:message) { super().gsub(/column (.*) is/, 'column toto is') }
+      let(:message) { super().gsub(/column (.*?) is/, 'column toto is').gsub(/Key \((.*?)\)=/, 'Key (toto)=') }
 
       it "returns nil" do
         expect(subject.exception_validator(uniqueness_exception)).to be_nil

spec/rescuer_spec.rb

@@ -13,3 +13,34 @@
     end
   end
 end
+
+shared_examples 'a model with rescued unique error without validator' do
+  describe 'create!' do
+    context 'when catching a race condition' do
+      before {
+        described_class.create!(relation_id: 1, handle: 'toto')
+      }
+
+      it 'adds an error on the model' do
+        model = described_class.create(relation_id: 1, handle: 'toto')
+        expect(model.errors[:handle]).to eq(["handle must be unique for this relation"])
+      end
+    end
+  end
+end
+
+describe Sqlite3Model do
+  it_behaves_like 'a model with rescued unique error without validator'
+end
+
+if defined?(MysqlModel)
+  describe MysqlModel do
+    it_behaves_like 'a model with rescued unique error without validator'
+  end
+end
+
+if defined?(PostgresqlModel)
+  describe PostgresqlModel do
+    it_behaves_like 'a model with rescued unique error without validator'
+  end
+end

spec/support/model.rb

@@ -17,10 +17,14 @@ def self.recreate_table(name, *args, &block)
     execute "drop table if exists #{name}"
 
     create_table(name, *args) do |t|
+      t.integer :relation_id
+      t.string :handle
+
       t.string :name
       t.integer :size
     end
 
+    add_index name, [:relation_id, :handle], unique: true
     add_index name, :name, unique: true
     add_index name, :size, unique: true
   end
@@ -49,8 +53,10 @@ module TestModel
   extend ActiveSupport::Concern
 
   included do
-    validates_uniqueness_of :name, rescue_from_duplicate: true
-    validates_uniqueness_of :size
+    rescue_from_duplicate :handle, scope: :relation_id, message: "handle must be unique for this relation"
+
+    validates_uniqueness_of :name, rescue_from_duplicate: true, allow_nil: true
+    validates_uniqueness_of :size, allow_nil: true
   end
 end