Existance checks for create and drop enums and cascade: true for drop_enum

lib/active_record/postgres_enum/postgresql_adapter.rb

@@ -42,13 +42,19 @@ def enums
         end
       end
 
-      def create_enum(name, values)
+      def create_enum(name, values, if_not_exists: nil)
+        return if if_not_exists && enums.include?(name.to_sym)
+
         values = values.map { |v| quote v }
         execute "CREATE TYPE #{name} AS ENUM (#{values.join(', ')})"
       end
 
-      def drop_enum(name)
-        execute "DROP TYPE #{name}"
+      def drop_enum(name, cascade: nil, if_exists: nil)
+        if_exists_statement = 'IF EXISTS' if if_exists
+        cascade_statement = 'CASCADE' if cascade
+
+        sql = "DROP TYPE #{if_exists_statement} #{name} #{cascade_statement}"
+        execute sql
       end
 
       def rename_enum(name, new_name)

spec/active_record/postgres_enum_spec.rb

@@ -20,11 +20,44 @@
       expect(connection.enums[:foo]).to eq %w(a1 a2)
     end
 
+    it "creates an enum if not exists" do
+      expect { connection.create_enum(:foo, %w(a1 a2), if_not_exists: true) }.not_to raise_error
+    end
+
+    it "fails create an existing enum" do
+      expect { connection.create_enum(:foo, %w(a1 a2)) }.to raise_error StandardError
+    end
+
     it "drops an enum" do
       expect { connection.drop_enum(:foo) }.to_not raise_error
       expect(connection.enums[:foo]).to be_nil
     end
 
+    it "drops an enum if exists" do
+      expect { connection.drop_enum(:some_unknown_type, if_exists: true) }.to_not raise_error
+    end
+
+    it "fails drop a non existing enum" do
+      expect { connection.drop_enum(:some_unknown_type) }.to raise_error StandardError
+    end
+
+    context 'drops an enum with cascade' do
+      before do
+        connection.create_table :test_tbl_for_cascade do |t|
+          t.enum :baz, enum_name: :foo
+        end
+      end
+
+      it "fails drop an enum with cascade" do
+        expect { connection.drop_enum(:foo) }.to raise_error StandardError
+      end
+
+      it "drops an enum with cascade" do
+        expect { connection.drop_enum(:foo, cascade: true) }.to_not raise_error
+        expect(connection.columns('test_tbl_for_cascade').map(&:name)).to_not include('baz')
+      end
+    end
+
     it "renames an enum" do
       expect { connection.rename_enum(:foo, :bar) }.to_not raise_error
       expect(connection.enums[:bar]).to eq %w(a1 a2)
@@ -40,8 +73,8 @@
     end
 
     it "fails to add an enum value if exists" do
-      expect { connection.add_enum_value(:foo, "a1", if_not_exists: false) }.to raise_error
-      expect { connection.add_enum_value(:foo, "a2") }.to raise_error
+      expect { connection.add_enum_value(:foo, "a1", if_not_exists: false) }.to raise_error StandardError
+      expect { connection.add_enum_value(:foo, "a2") }.to raise_error StandardError
     end
 
     it "adds an enum value after a given value" do