1 files changed, 36 insertions, 39 deletions

diff --git a/activerecord/lib/active_record/migration/compatibility.rb b/activerecord/lib/active_record/migration/compatibility.rb
index 74833f938f..2904634eb7 100644
--- a/activerecord/lib/active_record/migration/compatibility.rb
+++ b/activerecord/lib/active_record/migration/compatibility.rb
@@ -5,7 +5,7 @@ module ActiveRecord
         version = version.to_s
         name = "V#{version.tr('.', '_')}"
         unless const_defined?(name)
-          versions = constants.grep(/\AV[0-9_]+\z/).map { |s| s.to_s.delete('V').tr('_', '.').inspect }
+          versions = constants.grep(/\AV[0-9_]+\z/).map { |s| s.to_s.delete("V").tr("_", ".").inspect }
           raise ArgumentError, "Unknown migration version #{version.inspect}; expected one of #{versions.sort.join(', ')}"
         end
         const_get(name)
@@ -13,7 +13,27 @@ module ActiveRecord
 
       V5_1 = Current
 
-      module FourTwoShared
+      class V5_0 < V5_1
+        def create_table(table_name, options = {})
+          if adapter_name == "PostgreSQL"
+            if options[:id] == :uuid && !options[:default]
+              options[:default] = "uuid_generate_v4()"
+            end
+          end
+
+          # Since 5.1 Postgres adapter uses bigserial type for primary
+          # keys by default and MySQL uses bigint. This compat layer makes old migrations utilize
+          # serial/int type instead -- the way it used to work before 5.1.
+          if options[:id].blank?
+            options[:id] = :integer
+            options[:auto_increment] = true
+          end
+
+          super
+        end
+      end
+
+      class V4_2 < V5_0
         module TableDefinition
           def references(*, **options)
             options[:index] ||= false
@@ -21,7 +41,7 @@ module ActiveRecord
           end
           alias :belongs_to :references
 
-          def timestamps(*, **options)
+          def timestamps(**options)
             options[:null] = true if options[:null].nil?
             super
           end
@@ -59,7 +79,7 @@ module ActiveRecord
         end
         alias :add_belongs_to :add_reference
 
-        def add_timestamps(*, **options)
+        def add_timestamps(_, **options)
           options[:null] = true if options[:null].nil?
           super
         end
@@ -83,46 +103,23 @@ module ActiveRecord
 
         private
 
-        def index_name_for_remove(table_name, options = {})
-          index_name = index_name(table_name, options)
+          def index_name_for_remove(table_name, options = {})
+            index_name = index_name(table_name, options)
+
+            unless index_name_exists?(table_name, index_name, true)
+              if options.is_a?(Hash) && options.has_key?(:name)
+                options_without_column = options.dup
+                options_without_column.delete :column
+                index_name_without_column = index_name(table_name, options_without_column)
 
-          unless index_name_exists?(table_name, index_name, true)
-            if options.is_a?(Hash) && options.has_key?(:name)
-              options_without_column = options.dup
-              options_without_column.delete :column
-              index_name_without_column = index_name(table_name, options_without_column)
+                return index_name_without_column if index_name_exists?(table_name, index_name_without_column, false)
+              end
 
-              return index_name_without_column if index_name_exists?(table_name, index_name_without_column, false)
+              raise ArgumentError, "Index name '#{index_name}' on table '#{table_name}' does not exist"
             end
 
-            raise ArgumentError, "Index name '#{index_name}' on table '#{table_name}' does not exist"
+            index_name
           end
-
-          index_name
-        end
-      end
-
-      class V5_0 < V5_1
-      end
-
-      class V4_2 < V5_0
-        # 4.2 is defined as a module because it needs to be shared with
-        # Legacy. When the time comes, V5_0 should be defined straight
-        # in its class.
-        include FourTwoShared
-      end
-
-      module Legacy
-        include FourTwoShared
-
-        def migrate(*)
-          ActiveSupport::Deprecation.warn \
-            "Directly inheriting from ActiveRecord::Migration is deprecated. " \
-            "Please specify the Rails release the migration was written for:\n" \
-            "\n" \
-            "  class #{self.class.name} < ActiveRecord::Migration[4.2]"
-          super
-        end
       end
     end
   end