Remove :timestamp column type

The `:timestamp` type for columns is unused. All database adapters treat
them as the same database type. All code in `ActiveRecord` which changes
its behavior based on the column's type acts the same in both cases.
However, when the type is passed to code that checks for the `:datetime`
type, but not `:timestamp` (such as XML serialization), the result is
unexpected behavior.

Existing schema definitions will continue to work, and the `timestamp`
type is transparently aliased to `datetime`.

5 files changed, 30 insertions, 21 deletions

diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 38e93288e4..495b43c9e5 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -516,7 +516,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   end
 
   def test_only_time_related_columns_are_meant_to_be_cached_by_default
-    expected = %w(datetime timestamp time date).sort
+    expected = %w(datetime time date).sort
     assert_equal expected, ActiveRecord::Base.attribute_types_cached_by_default.map(&:to_s).sort
   end
 
diff --git a/activerecord/test/cases/column_test.rb b/activerecord/test/cases/column_test.rb
index 91605a52f9..fffcb19e56 100644
--- a/activerecord/test/cases/column_test.rb
+++ b/activerecord/test/cases/column_test.rb
@@ -109,19 +109,14 @@ module ActiveRecord
       end
 
       def test_type_cast_datetime_and_timestamp
-        columns = [
-          Column.new("field", nil, Type::DateTime.new),
-          Column.new("field", nil, Type::Timestamp.new),
-        ]
-        columns.each do |column|
-          assert_equal nil, column.type_cast(nil)
-          assert_equal nil, column.type_cast('')
-          assert_equal nil, column.type_cast('  ')
-          assert_equal nil, column.type_cast('ABC')
-
-          datetime_string = Time.now.utc.strftime("%FT%T")
-          assert_equal datetime_string, column.type_cast(datetime_string).strftime("%FT%T")
-        end
+        column = Column.new("field", nil, Type::DateTime.new)
+        assert_equal nil, column.type_cast(nil)
+        assert_equal nil, column.type_cast('')
+        assert_equal nil, column.type_cast('  ')
+        assert_equal nil, column.type_cast('ABC')
+
+        datetime_string = Time.now.utc.strftime("%FT%T")
+        assert_equal datetime_string, column.type_cast(datetime_string).strftime("%FT%T")
       end
 
       def test_type_cast_date
diff --git a/activerecord/test/cases/connection_adapters/type/type_map_test.rb b/activerecord/test/cases/connection_adapters/type/type_map_test.rb
index 565f44eef8..300c2ed225 100644
--- a/activerecord/test/cases/connection_adapters/type/type_map_test.rb
+++ b/activerecord/test/cases/connection_adapters/type/type_map_test.rb
@@ -21,7 +21,7 @@ module ActiveRecord
 
         def test_overriding_registered_types
           time = Time.new
-          timestamp = Timestamp.new
+          timestamp = DateTime.new
           mapping = TypeMap.new
 
           mapping.register_type(/time/i, time)
@@ -51,7 +51,7 @@ module ActiveRecord
 
         def test_changing_type_changes_aliases
           time = Time.new
-          timestamp = Timestamp.new
+          timestamp = DateTime.new
           mapping = TypeMap.new
 
           mapping.register_type(/timestamp/i, time)
diff --git a/activerecord/test/cases/connection_adapters/type_lookup_test.rb b/activerecord/test/cases/connection_adapters/type_lookup_test.rb
index a5b01260d3..18df30faf5 100644
--- a/activerecord/test/cases/connection_adapters/type_lookup_test.rb
+++ b/activerecord/test/cases/connection_adapters/type_lookup_test.rb
@@ -45,14 +45,11 @@ module ActiveRecord
         assert_lookup_type :time, 'TIME'
       end
 
-      def test_timestamp_types
-        assert_lookup_type :timestamp, 'timestamp'
-        assert_lookup_type :timestamp, 'TIMESTAMP'
-      end
-
       def test_datetime_types
         assert_lookup_type :datetime, 'datetime'
         assert_lookup_type :datetime, 'DATETIME'
+        assert_lookup_type :datetime, 'timestamp'
+        assert_lookup_type :datetime, 'TIMESTAMP'
       end
 
       def test_decimal_types
diff --git a/activerecord/test/cases/migration/change_schema_test.rb b/activerecord/test/cases/migration/change_schema_test.rb
index cbad718b43..b63dcf4459 100644
--- a/activerecord/test/cases/migration/change_schema_test.rb
+++ b/activerecord/test/cases/migration/change_schema_test.rb
@@ -233,6 +233,23 @@ module ActiveRecord
         end
       end
 
+      def test_add_column_with_timestamp_type
+        connection.create_table :testings do |t|
+          t.column :foo, :timestamp
+        end
+
+        klass = Class.new(ActiveRecord::Base)
+        klass.table_name = 'testings'
+
+        assert_equal :datetime, klass.columns_hash['foo'].type
+
+        if current_adapter?(:PostgreSQLAdapter)
+          assert_equal 'timestamp without time zone', klass.columns_hash['foo'].sql_type
+        else
+          assert_equal klass.connection.type_to_sql('datetime'), klass.columns_hash['foo'].sql_type
+        end
+      end
+
       def test_change_column_quotes_column_names
         connection.create_table :testings do |t|
           t.column :select, :string