Implement check_function_bodies only for Postgres

lib/fx/adapters/postgres.rb

@@ -69,7 +69,7 @@ def triggers
       #
       # @return [void]
       def create_function(sql_definition)
-        execute sql_definition
+        execute with_check_function_bodies(sql_definition)
       end
 
       # Creates a trigger in the database.
@@ -162,6 +162,18 @@ def support_drop_function_without_args
         pg_connection = connectable.connection.raw_connection
         pg_connection.server_version >= 10_00_00
       end
+
+      def with_check_function_bodies(sql_definition)
+        should_wrap = [true, false].include?(Fx.configuration.check_function_bodies)
+        return sql_definition unless should_wrap
+
+        <<-SQL
+          BEGIN;
+          SET LOCAL check_function_bodies TO #{Fx.configuration.check_function_bodies};
+          #{sql_definition}
+          COMMIT;
+        SQL
+      end
     end
   end
 end

lib/fx/configuration.rb

@@ -40,9 +40,25 @@ class Configuration
     # @return Boolean
     attr_accessor :dump_functions_at_beginning_of_schema
 
+    # Check function bodies during creation by issuing
+    # `SET LOCAL check_function_bodies TO <<value>>;` before creating functions.
+    #
+    # This is only useful with the Postgresql adapter.
+    #
+    # See https://stackoverflow.com/a/36983831 and
+    # https://www.postgresql.org/docs/9.5/runtime-config-client.html#GUC-CHECK-FUNCTION-BODIES
+    #
+    # Set to `nil` to use the database default configuration.
+    # The default and recommended value is `false` to mimic pg_dump's behavior.
+    #
+    # Defaults to false
+    # @return Boolean, nil
+    attr_accessor :check_function_bodies
+
     def initialize
       @database = Fx::Adapters::Postgres.new
       @dump_functions_at_beginning_of_schema = false
+      @check_function_bodies = false
     end
   end
 end