pep-484 for sqlalchemy.event; use future annotations

__future__.annotations mode allows us to use non-string
annotations for argument and return types in most cases,
but more importantly it removes a large amount of runtime
overhead that would be spent in evaluating the annotations.

Change-Id: I2f5b6126fe0019713fc50001be3627b664019ede
References: #6810

33 files changed, 80 insertions, 9 deletions

diff --git a/lib/sqlalchemy/orm/__init__.py b/lib/sqlalchemy/orm/__init__.py
index bbed93310..5a8a0f6cf 100644
--- a/lib/sqlalchemy/orm/__init__.py
+++ b/lib/sqlalchemy/orm/__init__.py
@@ -13,6 +13,8 @@ documentation for an overview of how this module is used.
 
 """
 
+from __future__ import annotations
+
 from . import exc as exc
 from . import mapper as mapperlib
 from . import strategy_options as strategy_options
diff --git a/lib/sqlalchemy/orm/_orm_constructors.py b/lib/sqlalchemy/orm/_orm_constructors.py
index a1f1faa05..8e05c6ef2 100644
--- a/lib/sqlalchemy/orm/_orm_constructors.py
+++ b/lib/sqlalchemy/orm/_orm_constructors.py
@@ -5,6 +5,8 @@
 # This module is part of SQLAlchemy and is released under
 # the MIT License: https://www.opensource.org/licenses/mit-license.php
 
+from __future__ import annotations
+
 import typing
 from typing import Any
 from typing import Collection
@@ -59,7 +61,7 @@ SynonymProperty = Synonym
     "for entities to be matched up to a query that is established "
     "via :meth:`.Query.from_statement` and now does nothing.",
 )
-def contains_alias(alias) -> "AliasOption":
+def contains_alias(alias) -> AliasOption:
     r"""Return a :class:`.MapperOption` that will indicate to the
     :class:`_query.Query`
     that the main table has been aliased.
@@ -74,7 +76,7 @@ def contains_alias(alias) -> "AliasOption":
 
 @overload
 def mapped_column(
-    __type: Union[Type["TypeEngine[_T]"], "TypeEngine[_T]"],
+    __type: Union[Type[TypeEngine[_T]], TypeEngine[_T]],
     *args: SchemaEventTarget,
     nullable: Literal[None] = ...,
     primary_key: Literal[None] = ...,
@@ -87,7 +89,7 @@ def mapped_column(
 @overload
 def mapped_column(
     __name: str,
-    __type: Union[Type["TypeEngine[_T]"], "TypeEngine[_T]"],
+    __type: Union[Type[TypeEngine[_T]], TypeEngine[_T]],
     *args: SchemaEventTarget,
     nullable: Literal[None] = ...,
     primary_key: Literal[None] = ...,
@@ -100,7 +102,7 @@ def mapped_column(
 @overload
 def mapped_column(
     __name: str,
-    __type: Union[Type["TypeEngine[_T]"], "TypeEngine[_T]"],
+    __type: Union[Type[TypeEngine[_T]], TypeEngine[_T]],
     *args: SchemaEventTarget,
     nullable: Literal[True] = ...,
     primary_key: Literal[None] = ...,
@@ -112,7 +114,7 @@ def mapped_column(
 
 @overload
 def mapped_column(
-    __type: Union[Type["TypeEngine[_T]"], "TypeEngine[_T]"],
+    __type: Union[Type[TypeEngine[_T]], TypeEngine[_T]],
     *args: SchemaEventTarget,
     nullable: Literal[True] = ...,
     primary_key: Literal[None] = ...,
@@ -125,7 +127,7 @@ def mapped_column(
 @overload
 def mapped_column(
     __name: str,
-    __type: Union[Type["TypeEngine[_T]"], "TypeEngine[_T]"],
+    __type: Union[Type[TypeEngine[_T]], TypeEngine[_T]],
     *args: SchemaEventTarget,
     nullable: Literal[False] = ...,
     primary_key: Literal[None] = ...,
@@ -137,7 +139,7 @@ def mapped_column(
 
 @overload
 def mapped_column(
-    __type: Union[Type["TypeEngine[_T]"], "TypeEngine[_T]"],
+    __type: Union[Type[TypeEngine[_T]], TypeEngine[_T]],
     *args: SchemaEventTarget,
     nullable: Literal[False] = ...,
     primary_key: Literal[None] = ...,
@@ -149,7 +151,7 @@ def mapped_column(
 
 @overload
 def mapped_column(
-    __type: Union[Type["TypeEngine[_T]"], "TypeEngine[_T]"],
+    __type: Union[Type[TypeEngine[_T]], TypeEngine[_T]],
     *args: SchemaEventTarget,
     nullable: bool = ...,
     primary_key: Literal[True] = ...,
@@ -162,7 +164,7 @@ def mapped_column(
 @overload
 def mapped_column(
     __name: str,
-    __type: Union[Type["TypeEngine[_T]"], "TypeEngine[_T]"],
+    __type: Union[Type[TypeEngine[_T]], TypeEngine[_T]],
     *args: SchemaEventTarget,
     nullable: bool = ...,
     primary_key: Literal[True] = ...,
diff --git a/lib/sqlalchemy/orm/attributes.py b/lib/sqlalchemy/orm/attributes.py
index fbfb2b2ee..c4afdb3a9 100644
--- a/lib/sqlalchemy/orm/attributes.py
+++ b/lib/sqlalchemy/orm/attributes.py
@@ -13,6 +13,9 @@ defines a large part of the ORM's interactivity.
 
 
 """
+
+from __future__ import annotations
+
 from collections import namedtuple
 import operator
 from typing import Any
diff --git a/lib/sqlalchemy/orm/base.py b/lib/sqlalchemy/orm/base.py
index e6d4a6729..33367c0c6 100644
--- a/lib/sqlalchemy/orm/base.py
+++ b/lib/sqlalchemy/orm/base.py
@@ -9,6 +9,8 @@
 
 """
 
+from __future__ import annotations
+
 import operator
 import typing
 from typing import Any
diff --git a/lib/sqlalchemy/orm/clsregistry.py b/lib/sqlalchemy/orm/clsregistry.py
index 037b70257..d0cb53e29 100644
--- a/lib/sqlalchemy/orm/clsregistry.py
+++ b/lib/sqlalchemy/orm/clsregistry.py
@@ -10,6 +10,9 @@ This system allows specification of classes and expressions used in
 :func:`_orm.relationship` using strings.
 
 """
+
+from __future__ import annotations
+
 import re
 from typing import MutableMapping
 from typing import Union
diff --git a/lib/sqlalchemy/orm/collections.py b/lib/sqlalchemy/orm/collections.py
index ba4225563..00ae9dac7 100644
--- a/lib/sqlalchemy/orm/collections.py
+++ b/lib/sqlalchemy/orm/collections.py
@@ -102,6 +102,8 @@ The owning object and :class:`.CollectionAttributeImpl` are also reachable
 through the adapter, allowing for some very sophisticated behavior.
 
 """
+from __future__ import annotations
+
 import operator
 import threading
 import typing
diff --git a/lib/sqlalchemy/orm/context.py b/lib/sqlalchemy/orm/context.py
index 34f291864..f51abde0c 100644
--- a/lib/sqlalchemy/orm/context.py
+++ b/lib/sqlalchemy/orm/context.py
@@ -4,6 +4,9 @@
 #
 # This module is part of SQLAlchemy and is released under
 # the MIT License: https://www.opensource.org/licenses/mit-license.php
+
+from __future__ import annotations
+
 import itertools
 from typing import List
 
diff --git a/lib/sqlalchemy/orm/decl_api.py b/lib/sqlalchemy/orm/decl_api.py
index 5ac9966dd..4e28eeff7 100644
--- a/lib/sqlalchemy/orm/decl_api.py
+++ b/lib/sqlalchemy/orm/decl_api.py
@@ -5,6 +5,9 @@
 # This module is part of SQLAlchemy and is released under
 # the MIT License: https://www.opensource.org/licenses/mit-license.php
 """Public API functions and helpers for declarative."""
+
+from __future__ import annotations
+
 import itertools
 import re
 import typing
diff --git a/lib/sqlalchemy/orm/dependency.py b/lib/sqlalchemy/orm/dependency.py
index 14812f2c2..d05d27b0e 100644
--- a/lib/sqlalchemy/orm/dependency.py
+++ b/lib/sqlalchemy/orm/dependency.py
@@ -9,6 +9,8 @@
 
 """
 
+from __future__ import annotations
+
 from . import attributes
 from . import exc
 from . import sync
diff --git a/lib/sqlalchemy/orm/descriptor_props.py b/lib/sqlalchemy/orm/descriptor_props.py
index 4526a8b33..4616e4094 100644
--- a/lib/sqlalchemy/orm/descriptor_props.py
+++ b/lib/sqlalchemy/orm/descriptor_props.py
@@ -10,6 +10,8 @@ that exist as configurational elements, but don't participate
 as actively in the load/persist ORM loop.
 
 """
+from __future__ import annotations
+
 import inspect
 import itertools
 import operator
diff --git a/lib/sqlalchemy/orm/dynamic.py b/lib/sqlalchemy/orm/dynamic.py
index 3d9c61c20..52a6ec4b0 100644
--- a/lib/sqlalchemy/orm/dynamic.py
+++ b/lib/sqlalchemy/orm/dynamic.py
@@ -12,6 +12,8 @@ basic add/delete mutation.
 
 """
 
+from __future__ import annotations
+
 from . import attributes
 from . import exc as orm_exc
 from . import interfaces
diff --git a/lib/sqlalchemy/orm/evaluator.py b/lib/sqlalchemy/orm/evaluator.py
index 61e3f6e90..453fc8903 100644
--- a/lib/sqlalchemy/orm/evaluator.py
+++ b/lib/sqlalchemy/orm/evaluator.py
@@ -5,6 +5,8 @@
 # This module is part of SQLAlchemy and is released under
 # the MIT License: https://www.opensource.org/licenses/mit-license.php
 
+from __future__ import annotations
+
 import operator
 
 from .. import exc
diff --git a/lib/sqlalchemy/orm/events.py b/lib/sqlalchemy/orm/events.py
index cc4bedc3f..e62a83397 100644
--- a/lib/sqlalchemy/orm/events.py
+++ b/lib/sqlalchemy/orm/events.py
@@ -8,6 +8,8 @@
 """ORM event interfaces.
 
 """
+from __future__ import annotations
+
 import weakref
 
 from . import instrumentation
diff --git a/lib/sqlalchemy/orm/exc.py b/lib/sqlalchemy/orm/exc.py
index 8dd4d90d6..f70ea7837 100644
--- a/lib/sqlalchemy/orm/exc.py
+++ b/lib/sqlalchemy/orm/exc.py
@@ -6,6 +6,9 @@
 # the MIT License: https://www.opensource.org/licenses/mit-license.php
 
 """SQLAlchemy ORM exceptions."""
+
+from __future__ import annotations
+
 from .. import exc as sa_exc
 from .. import util
 from ..exc import MultipleResultsFound  # noqa
diff --git a/lib/sqlalchemy/orm/identity.py b/lib/sqlalchemy/orm/identity.py
index f8204ec77..3caf0b22f 100644
--- a/lib/sqlalchemy/orm/identity.py
+++ b/lib/sqlalchemy/orm/identity.py
@@ -5,6 +5,8 @@
 # This module is part of SQLAlchemy and is released under
 # the MIT License: https://www.opensource.org/licenses/mit-license.php
 
+from __future__ import annotations
+
 import weakref
 
 from . import util as orm_util
diff --git a/lib/sqlalchemy/orm/instrumentation.py b/lib/sqlalchemy/orm/instrumentation.py
index 5d0b57206..a050c533a 100644
--- a/lib/sqlalchemy/orm/instrumentation.py
+++ b/lib/sqlalchemy/orm/instrumentation.py
@@ -30,6 +30,8 @@ alternate instrumentation forms.
 """
 
 
+from __future__ import annotations
+
 from . import base
 from . import collections
 from . import exc
diff --git a/lib/sqlalchemy/orm/interfaces.py b/lib/sqlalchemy/orm/interfaces.py
index 1f9ec78f7..eed973526 100644
--- a/lib/sqlalchemy/orm/interfaces.py
+++ b/lib/sqlalchemy/orm/interfaces.py
@@ -16,6 +16,8 @@ are exposed when inspecting mappings.
 
 """
 
+from __future__ import annotations
+
 import collections
 import typing
 from typing import Any
diff --git a/lib/sqlalchemy/orm/loading.py b/lib/sqlalchemy/orm/loading.py
index a40437c67..16ab1f4c8 100644
--- a/lib/sqlalchemy/orm/loading.py
+++ b/lib/sqlalchemy/orm/loading.py
@@ -13,6 +13,8 @@ as well as some of the attribute loading strategies.
 
 """
 
+from __future__ import annotations
+
 from . import attributes
 from . import exc as orm_exc
 from . import path_registry
diff --git a/lib/sqlalchemy/orm/mapped_collection.py b/lib/sqlalchemy/orm/mapped_collection.py
index 75abeef4c..4324a000d 100644
--- a/lib/sqlalchemy/orm/mapped_collection.py
+++ b/lib/sqlalchemy/orm/mapped_collection.py
@@ -5,6 +5,8 @@
 # This module is part of SQLAlchemy and is released under
 # the MIT License: https://www.opensource.org/licenses/mit-license.php
 
+from __future__ import annotations
+
 import operator
 from typing import Any
 from typing import Callable
diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index cd0d1e820..15e9b8431 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -14,6 +14,8 @@ This is a semi-private module; the main configurational API of the ORM is
 available in :class:`~sqlalchemy.orm.`.
 
 """
+from __future__ import annotations
+
 from collections import deque
 from functools import reduce
 from itertools import chain
diff --git a/lib/sqlalchemy/orm/path_registry.py b/lib/sqlalchemy/orm/path_registry.py
index 0d87739cc..9a7aa91a0 100644
--- a/lib/sqlalchemy/orm/path_registry.py
+++ b/lib/sqlalchemy/orm/path_registry.py
@@ -8,6 +8,8 @@
 
 """
 
+from __future__ import annotations
+
 from functools import reduce
 from itertools import chain
 import logging
diff --git a/lib/sqlalchemy/orm/persistence.py b/lib/sqlalchemy/orm/persistence.py
index b3381b039..519eb393f 100644
--- a/lib/sqlalchemy/orm/persistence.py
+++ b/lib/sqlalchemy/orm/persistence.py
@@ -13,6 +13,8 @@ The functions here are called only by the unit of work functions
 in unitofwork.py.
 
 """
+from __future__ import annotations
+
 from itertools import chain
 from itertools import groupby
 from itertools import zip_longest
diff --git a/lib/sqlalchemy/orm/properties.py b/lib/sqlalchemy/orm/properties.py
index f28c45fab..9f9ca90cb 100644
--- a/lib/sqlalchemy/orm/properties.py
+++ b/lib/sqlalchemy/orm/properties.py
@@ -12,6 +12,8 @@ mapped attributes.
 
 """
 
+from __future__ import annotations
+
 from typing import Any
 from typing import cast
 from typing import List
diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index 61174487a..3b4b082a4 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -18,6 +18,8 @@ ORM session, whereas the ``Select`` construct interacts directly with the
 database to return iterable result sets.
 
 """
+from __future__ import annotations
+
 import collections.abc as collections_abc
 import itertools
 import operator
diff --git a/lib/sqlalchemy/orm/scoping.py b/lib/sqlalchemy/orm/scoping.py
index 47da85716..9eb80a107 100644
--- a/lib/sqlalchemy/orm/scoping.py
+++ b/lib/sqlalchemy/orm/scoping.py
@@ -5,6 +5,8 @@
 # This module is part of SQLAlchemy and is released under
 # the MIT License: https://www.opensource.org/licenses/mit-license.php
 
+from __future__ import annotations
+
 from . import exc as orm_exc
 from .base import class_mapper
 from .session import Session
diff --git a/lib/sqlalchemy/orm/session.py b/lib/sqlalchemy/orm/session.py
index 6911ab505..4140d52c5 100644
--- a/lib/sqlalchemy/orm/session.py
+++ b/lib/sqlalchemy/orm/session.py
@@ -6,6 +6,8 @@
 # the MIT License: https://www.opensource.org/licenses/mit-license.php
 """Provides the Session class and related utilities."""
 
+from __future__ import annotations
+
 import contextlib
 import itertools
 import sys
diff --git a/lib/sqlalchemy/orm/state.py b/lib/sqlalchemy/orm/state.py
index 01ee16a13..58fa3e41a 100644
--- a/lib/sqlalchemy/orm/state.py
+++ b/lib/sqlalchemy/orm/state.py
@@ -12,6 +12,8 @@ defines a large part of the ORM's interactivity.
 
 """
 
+from __future__ import annotations
+
 import weakref
 
 from . import base
diff --git a/lib/sqlalchemy/orm/state_changes.py b/lib/sqlalchemy/orm/state_changes.py
index 1421c1ae9..1afeab05b 100644
--- a/lib/sqlalchemy/orm/state_changes.py
+++ b/lib/sqlalchemy/orm/state_changes.py
@@ -8,6 +8,8 @@
 
 """
 
+from __future__ import annotations
+
 import contextlib
 from enum import Enum
 from typing import Any
diff --git a/lib/sqlalchemy/orm/strategies.py b/lib/sqlalchemy/orm/strategies.py
index 316aa7ed7..85e015193 100644
--- a/lib/sqlalchemy/orm/strategies.py
+++ b/lib/sqlalchemy/orm/strategies.py
@@ -8,6 +8,8 @@
 """sqlalchemy.orm.interfaces.LoaderStrategy
    implementations, and related MapperOptions."""
 
+from __future__ import annotations
+
 import collections
 import itertools
 
diff --git a/lib/sqlalchemy/orm/strategy_options.py b/lib/sqlalchemy/orm/strategy_options.py
index 3f093e543..63679dd27 100644
--- a/lib/sqlalchemy/orm/strategy_options.py
+++ b/lib/sqlalchemy/orm/strategy_options.py
@@ -8,6 +8,8 @@
 
 """
 
+from __future__ import annotations
+
 import typing
 from typing import Any
 from typing import cast
diff --git a/lib/sqlalchemy/orm/sync.py b/lib/sqlalchemy/orm/sync.py
index 2994841f5..a49bd6f8e 100644
--- a/lib/sqlalchemy/orm/sync.py
+++ b/lib/sqlalchemy/orm/sync.py
@@ -10,6 +10,8 @@ between instances based on join conditions.
 
 """
 
+from __future__ import annotations
+
 from . import attributes
 from . import exc
 from . import util as orm_util
diff --git a/lib/sqlalchemy/orm/unitofwork.py b/lib/sqlalchemy/orm/unitofwork.py
index b478f427c..da098e8c5 100644
--- a/lib/sqlalchemy/orm/unitofwork.py
+++ b/lib/sqlalchemy/orm/unitofwork.py
@@ -13,6 +13,8 @@ organizes them in order of dependency, and executes.
 
 """
 
+from __future__ import annotations
+
 from . import attributes
 from . import exc as orm_exc
 from . import util as orm_util
diff --git a/lib/sqlalchemy/orm/util.py b/lib/sqlalchemy/orm/util.py
index 45c578355..e00e05954 100644
--- a/lib/sqlalchemy/orm/util.py
+++ b/lib/sqlalchemy/orm/util.py
@@ -5,6 +5,8 @@
 # This module is part of SQLAlchemy and is released under
 # the MIT License: https://www.opensource.org/licenses/mit-license.php
 
+from __future__ import annotations
+
 import re
 import types
 import typing