Adds Rails 6.1 if_exists flags

README.md

@@ -77,12 +77,16 @@ tweak the schema in the new definition and run the `update_function` migration.
 
 ## I don't need this trigger or function anymore. Make it go away.
 
-F(x) gives you `drop_trigger` and `drop_function` too:
+F(x) gives you `drop_trigger` and `drop_function` too. These support the Rails 6.1 `if_exists: true` flags
 
 ```ruby
 def change
   drop_function :uppercase_users_name, revert_to_version: 2
 end
+
+def up
+  drop_function :users_first_name, revert_to_version: 2, if_exists: true
+end
 ```
 
 ## What if I need to use a function as the default value of a column?

lib/fx/adapters/postgres.rb

@@ -122,13 +122,14 @@ def update_trigger(name, on:, sql_definition:)
       # {Fx::Statements::Function#drop_function}.
       #
       # @param name The name of the function to drop
+      # @param if_exists If true, will not raise an error if the function does not exist
       #
       # @return [void]
-      def drop_function(name)
+      def drop_function(name, if_exists: false)
         if connection.support_drop_function_without_args
-          execute("DROP FUNCTION #{name};")
+          execute("DROP FUNCTION #{if_exists ? 'IF EXISTS ' : ' '}#{name};")
         else
-          execute("DROP FUNCTION #{name}();")
+          execute("DROP FUNCTION #{if_exists ? 'IF EXISTS ' : ' '}#{name}();")
         end
       end
 
@@ -139,10 +140,11 @@ def drop_function(name)
       #
       # @param name The name of the trigger to drop
       # @param on The associated table for the trigger to drop
+      # @param if_exists If true, will not raise an error if the trigger does not exist
       #
       # @return [void]
-      def drop_trigger(name, on:)
-        execute("DROP TRIGGER #{name} ON #{on};")
+      def drop_trigger(name, on:, if_exists: false)
+        execute("DROP TRIGGER #{if_exists ? 'IF EXISTS ' : ' '}#{name} ON #{on};")
       end
 
       private

lib/fx/statements.rb

@@ -53,8 +53,12 @@ def create_function(name, options = {})
     # @example Drop a function, rolling back to version 2 on rollback
     #   drop_function(:uppercase_users_name, revert_to_version: 2)
     #
+    # @example Drop a function only if it exists
+    #   drop_function(:uppercase_users_name, if_exists: true)
+    #
     def drop_function(name, options = {})
-      Fx.database.drop_function(name)
+      if_exists = options.fetch(:if_exists, false)
+      Fx.database.drop_function(name, if_exists: if_exists)
     end
 
     # Update a database function.
@@ -160,9 +164,13 @@ def create_trigger(name, options = {})
     # @example Drop a trigger, rolling back to version 3 on rollback
     #   drop_trigger(:log_inserts, on: :users, revert_to_version: 3)
     #
+    # @example Drop a trigger only if it exists
+    #   drop_trigger(:log_inserts, on: :users, if_exists: true)
+    #
     def drop_trigger(name, options = {})
       on = options.fetch(:on)
-      Fx.database.drop_trigger(name, on: on)
+      if_exists = options.fetch(:if_exists, false)
+      Fx.database.drop_trigger(name, on: on, if_exists: if_exists)
     end
 
     # Update a database trigger to a new version.

spec/features/functions/migrations_spec.rb

@@ -37,6 +37,16 @@ def up
     expect { run_migration(migration, :up) }.not_to raise_error
   end
 
+  it "can run migrations that drop functions without raising an error" do
+    migration = Class.new(migration_class) do
+      def up
+        drop_function :test, if_exists: true # test has not been created
+      end
+    end
+
+    expect { run_migration(migration, :up) }.not_to raise_error
+  end
+
   it "can run migrations that updates functions" do
     connection.create_function(:test)
 

spec/features/functions/revert_spec.rb

@@ -47,6 +47,18 @@ def change
       )
   end
 
+  it "can run reversible migrations for dropping functions with if_exists" do
+    connection.create_function(:test)
+
+    good_migration = Class.new(migration_class) do
+      def change
+        drop_function :test, revert_to_version: 1, if_exists: true
+      end
+    end
+
+    expect { run_migration(good_migration, [:up, :down]) }.not_to raise_error
+  end
+
   it "can run reversible migrations for updating functions" do
     connection.create_function(:test)
 

spec/fx/adapters/postgres_spec.rb

@@ -91,6 +91,15 @@
         expect(adapter.functions.map(&:name)).not_to include("test")
       end
     end
+
+    context "when the function does not exist" do
+      it "successfully drops a function with if_exists = true" do
+        adapter = Fx::Adapters::Postgres.new
+        adapter.drop_function(:test, if_exists: true)
+
+        expect(adapter.functions.map(&:name)).not_to include("test")
+      end
+    end
   end
 
   describe "#functions" do

spec/fx/statements_spec.rb

@@ -46,7 +46,15 @@
 
       connection.drop_function(:test)
 
-      expect(database).to have_received(:drop_function).with(:test)
+      expect(database).to have_received(:drop_function).with(:test, if_exists: false)
+    end
+
+    it "drops the function with if_exists" do
+      database = stubbed_database
+
+      connection.drop_function(:test, if_exists: true)
+
+      expect(database).to have_received(:drop_function).with(:test, if_exists: true)
     end
   end
 
@@ -134,7 +142,16 @@
       connection.drop_trigger(:test, on: :users)
 
       expect(database).to have_received(:drop_trigger)
-        .with(:test, on: :users)
+        .with(:test, on: :users, if_exists: false)
+    end
+
+    it "drops the trigger with if_exists" do
+      database = stubbed_database
+
+      connection.drop_trigger(:test, on: :users, if_exists: true)
+
+      expect(database).to have_received(:drop_trigger)
+        .with(:test, on: :users, if_exists: true)
     end
   end