implement second-level type resolution for literals

Added additional rule to the system that determines ``TypeEngine``
implementations from Python literals to apply a second level of adjustment
to the type, so that a Python datetime with or without tzinfo can set the
``timezone=True`` parameter on the returned :class:`.DateTime` object, as
well as :class:`.Time`. This helps with some round-trip scenarios on
type-sensitive PostgreSQL dialects such as asyncpg, psycopg3 (2.0 only).

For 1.4 specifically, the backport improves support for asyncpg handling of
TIME WITH TIMEZONE, which was not fully implemented. 2.0's reworked
PostgreSQL architecture had this handled already.

Fixes: #7537
Change-Id: Icdb07db85af5f7f39f1c1ef855fe27609770094b

2 files changed, 28 insertions, 1 deletions

diff --git a/lib/sqlalchemy/sql/sqltypes.py b/lib/sqlalchemy/sql/sqltypes.py
index cda7b35cd..8a862d121 100644
--- a/lib/sqlalchemy/sql/sqltypes.py
+++ b/lib/sqlalchemy/sql/sqltypes.py
@@ -622,6 +622,13 @@ class DateTime(_LookupExpressionAdapter, TypeEngine):
     def get_dbapi_type(self, dbapi):
         return dbapi.DATETIME
 
+    def _resolve_for_literal(self, value):
+        with_timezone = value.tzinfo is not None
+        if with_timezone and not self.timezone:
+            return DATETIME_TIMEZONE
+        else:
+            return self
+
     @property
     def python_type(self):
         return dt.datetime
@@ -692,6 +699,13 @@ class Time(_LookupExpressionAdapter, TypeEngine):
     def python_type(self):
         return dt.time
 
+    def _resolve_for_literal(self, value):
+        with_timezone = value.tzinfo is not None
+        if with_timezone and not self.timezone:
+            return TIME_TIMEZONE
+        else:
+            return self
+
     @util.memoized_property
     def _expression_adaptations(self):
         # Based on https://www.postgresql.org/docs/current/\
@@ -2994,6 +3008,8 @@ STRINGTYPE = String()
 INTEGERTYPE = Integer()
 MATCHTYPE = MatchType()
 TABLEVALUE = TableValueType()
+DATETIME_TIMEZONE = DateTime(timezone=True)
+TIME_TIMEZONE = Time(timezone=True)
 
 _type_map = {
     int: Integer(),
@@ -3031,7 +3047,7 @@ def _resolve_value_to_type(value):
             )
         return NULLTYPE
     else:
-        return _result_type
+        return _result_type._resolve_for_literal(value)
 
 
 # back-assign to type_api
diff --git a/lib/sqlalchemy/sql/type_api.py b/lib/sqlalchemy/sql/type_api.py
index 07cd4d95f..b087dd1e9 100644
--- a/lib/sqlalchemy/sql/type_api.py
+++ b/lib/sqlalchemy/sql/type_api.py
@@ -592,6 +592,17 @@ class TypeEngine(Traversible):
         )
         return new_type
 
+    def _resolve_for_literal(self, value):
+        """adjust this type given a literal Python value that will be
+        stored in a bound parameter.
+
+        Used exclusively by _resolve_value_to_type().
+
+        .. versionadded:: 1.4.30 or 2.0
+
+        """
+        return self
+
     @util.memoized_property
     def _type_affinity(self):
         """Return a rudimental 'affinity' value expressing the general class