Correctly dump integer-like primary key with default nil

The PR #27384 changed integer-like primary key to be autoincrement
unless an explicit default. This means that integer-like primary key is
restored as autoincrement unless dumping the default nil explicitly.
We should dump integer-like primary key with default nil correctly.

4 files changed, 21 insertions, 20 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
index d6c912a69e..08406e6b2b 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
@@ -14,6 +14,8 @@ module ActiveRecord
         return {} if default_primary_key?(column)
         spec = { id: schema_type(column).inspect }
         spec.merge!(prepare_column_options(column).except!(:null))
+        spec[:default] ||= "nil" if explicit_primary_key_default?(column)
+        spec
       end
 
       # This can be overridden on an Adapter level basis to support other
@@ -59,6 +61,10 @@ module ActiveRecord
           schema_type(column) == :bigint
         end
 
+        def explicit_primary_key_default?(column)
+          false
+        end
+
         def schema_type_with_virtual(column)
           if supports_virtual_columns? && column.virtual?
             :virtual
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
index 7a277b8cfd..a06dd0f6b8 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
@@ -1,16 +1,7 @@
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
-      module ColumnDumper
-        def column_spec_for_primary_key(column)
-          spec = super
-          if [:integer, :bigint].include?(schema_type(column)) && !column.auto_increment?
-            spec[:default] ||= schema_default(column) || "nil"
-          end
-          spec[:unsigned] = "true" if column.unsigned?
-          spec
-        end
-
+      module ColumnDumper # :nodoc:
         def prepare_column_options(column)
           spec = super
           spec[:unsigned] = "true" if column.unsigned?
@@ -34,6 +25,10 @@ module ActiveRecord
             super && column.auto_increment?
           end
 
+          def explicit_primary_key_default?(column)
+            column.type == :integer && !column.auto_increment?
+          end
+
           def schema_type(column)
             if column.sql_type == "tinyblob"
               :blob
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
index 7808d37deb..5555a46b6b 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
@@ -1,15 +1,7 @@
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
-      module ColumnDumper
-        def column_spec_for_primary_key(column)
-          spec = super
-          if schema_type(column) == :uuid
-            spec[:default] ||= "nil"
-          end
-          spec
-        end
-
+      module ColumnDumper # :nodoc:
         # Adds +:array+ option to the default set
         def prepare_column_options(column)
           spec = super
@@ -28,6 +20,10 @@ module ActiveRecord
             schema_type(column) == :bigserial
           end
 
+          def explicit_primary_key_default?(column)
+            column.type == :uuid || (column.type == :integer && !column.serial?)
+          end
+
           def schema_type(column)
             return super unless column.serial?
 
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb
index c027fef83c..eec018eda3 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb
@@ -1,12 +1,16 @@
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
-      module ColumnDumper
+      module ColumnDumper # :nodoc:
         private
 
           def default_primary_key?(column)
             schema_type(column) == :integer
           end
+
+          def explicit_primary_key_default?(column)
+            column.bigint?
+          end
       end
     end
   end