Fix migration compatibility for default precision value on datetime c…

…olumns (Round 2)

add test cases on default precision from 4.2 to 6.1

Fix compatibility on rails 6.0

Fix compatibility from 5.2 to 4.2

activerecord/lib/active_record/migration/compatibility.rb

@@ -99,6 +99,11 @@ def references(*args, **options)
             end
           end
           alias :belongs_to :references
+
+          def column(name, type, index: nil, **options)
+            options[:precision] ||= nil
+            super
+          end
         end
 
         def create_table(table_name, **options)
@@ -146,6 +151,11 @@ def timestamps(**options)
             options[:precision] ||= nil
             super
           end
+
+          def column(name, type, index: nil, **options)
+            options[:precision] ||= nil
+            super
+          end
         end
 
         module CommandRecorder

activerecord/test/cases/migration/compatibility_test.rb

@@ -351,7 +351,127 @@ def migrate(x)
         connection.drop_table :more_testings rescue nil
       end
 
-      def test_datetime_doesnt_set_precision_on_change_table
+      def test_datetime_doesnt_set_precision_on_change_table_4_2
+        create_migration = Class.new(ActiveRecord::Migration[4.2]) {
+          def migrate(x)
+            create_table :more_testings do |t|
+              t.datetime :published_at
+            end
+          end
+        }.new
+
+        change_migration = Class.new(ActiveRecord::Migration[4.2]) {
+          def migrate(x)
+            change_table :more_testings do |t|
+              t.datetime :published_at, default: Time.now
+            end
+          end
+        }.new
+
+        ActiveRecord::Migrator.new(:up, [create_migration, change_migration], @schema_migration).migrate
+
+        assert connection.column_exists?(:more_testings, :published_at, **precision_implicit_default)
+      ensure
+        connection.drop_table :more_testings rescue nil
+      end
+
+      def test_datetime_doesnt_set_precision_on_change_table_5_0
+        create_migration = Class.new(ActiveRecord::Migration[5.0]) {
+          def migrate(x)
+            create_table :more_testings do |t|
+              t.datetime :published_at
+            end
+          end
+        }.new
+
+        change_migration = Class.new(ActiveRecord::Migration[5.0]) {
+          def migrate(x)
+            change_table :more_testings do |t|
+              t.datetime :published_at, default: Time.now
+            end
+          end
+        }.new
+
+        ActiveRecord::Migrator.new(:up, [create_migration, change_migration], @schema_migration).migrate
+
+        assert connection.column_exists?(:more_testings, :published_at, **precision_implicit_default)
+      ensure
+        connection.drop_table :more_testings rescue nil
+      end
+
+      def test_datetime_doesnt_set_precision_on_change_table_5_1
+        create_migration = Class.new(ActiveRecord::Migration[5.1]) {
+          def migrate(x)
+            create_table :more_testings do |t|
+              t.datetime :published_at
+            end
+          end
+        }.new
+
+        change_migration = Class.new(ActiveRecord::Migration[5.1]) {
+          def migrate(x)
+            change_table :more_testings do |t|
+              t.datetime :published_at, default: Time.now
+            end
+          end
+        }.new
+
+        ActiveRecord::Migrator.new(:up, [create_migration, change_migration], @schema_migration).migrate
+
+        assert connection.column_exists?(:more_testings, :published_at, **precision_implicit_default)
+      ensure
+        connection.drop_table :more_testings rescue nil
+      end
+
+      def test_datetime_doesnt_set_precision_on_change_table_5_2
+        create_migration = Class.new(ActiveRecord::Migration[5.2]) {
+          def migrate(x)
+            create_table :more_testings do |t|
+              t.datetime :published_at
+            end
+          end
+        }.new
+
+        change_migration = Class.new(ActiveRecord::Migration[5.2]) {
+          def migrate(x)
+            change_table :more_testings do |t|
+              t.datetime :published_at, default: Time.now
+            end
+          end
+        }.new
+
+        ActiveRecord::Migrator.new(:up, [create_migration, change_migration], @schema_migration).migrate
+
+        assert connection.column_exists?(:more_testings, :published_at, **precision_implicit_default)
+      ensure
+        connection.drop_table :more_testings rescue nil
+      end
+
+      def test_datetime_doesnt_set_precision_on_change_table_6_0
+        create_migration = Class.new(ActiveRecord::Migration[6.0]) {
+          def migrate(x)
+            create_table :more_testings do |t|
+              t.datetime :published_at
+            end
+          end
+        }.new
+
+        change_migration = Class.new(ActiveRecord::Migration[6.0]) {
+          def migrate(x)
+            change_table :more_testings do |t|
+              t.datetime :published_at, default: Time.now
+            end
+          end
+        }.new
+
+        ActiveRecord::Migrator.new(:up, [create_migration, change_migration], @schema_migration).migrate
+
+        assert connection.column_exists?(:more_testings, :published_at, **precision_implicit_default)
+      ensure
+        connection.drop_table :more_testings rescue nil
+      end
+
+      def test_datetime_doesnt_set_precision_on_change_table_6_1
         create_migration = Class.new(ActiveRecord::Migration[6.1]) {
           def migrate(x)
             create_table :more_testings do |t|