Enable F821

In Ia63a510f9c1d08b055eef62cf047f1f427f0450c we introduced
"lambda combinations" which use a bit of function closure inspection
in order to allow for testing combinations that make use of symbols that
come from test fixtures, or from the test itself.

Two problems.  One is that we can't use F821 flake8 rule without either
adding lots of noqas, skipping the file, or adding arguments to the
lambdas themselves that are then populated, which makes for a very
verbose system.  The other is that the system is already verbose
with all those lambdas and the magic in use is a non-explicit kind,
hence F821 reminds us that if we can improve upon this, we should.

So let's improve upon it by making it so that the "lambda" is just
once and up front for the whole thing, and let it accept the arguments
directly.   This still requires magic, because these test cases need
to resolve at test collection time, not test runtime.  But we will
instead substitute a namespace up front that can be coerced into
its desired form within the tests.

Additionally, there's a little bit of py2k compatible type annotations
present; f821 is checking these, so we have to add those imports
also using the TYPE_CHECKING boolean so they don't take place in
py2k.

Change-Id: Idb7e7a0c8af86d9ab133f548511306ef68cdba14

14 files changed, 88 insertions, 26 deletions

diff --git a/lib/sqlalchemy/dialects/mysql/pyodbc.py b/lib/sqlalchemy/dialects/mysql/pyodbc.py
index 6a411b984..eb62e6425 100644
--- a/lib/sqlalchemy/dialects/mysql/pyodbc.py
+++ b/lib/sqlalchemy/dialects/mysql/pyodbc.py
@@ -126,7 +126,7 @@ class MySQLDialect_pyodbc(PyODBCConnector, MySQLDialect):
                 conn.setdecoding(pyodbc_SQL_CHAR, encoding="utf-8")
                 conn.setdecoding(pyodbc_SQL_WCHAR, encoding="utf-8")
                 conn.setencoding(str, encoding="utf-8")
-                conn.setencoding(unicode, encoding="utf-8")
+                conn.setencoding(unicode, encoding="utf-8")  # noqa: F821
 
         return on_connect
 
diff --git a/lib/sqlalchemy/engine/mock.py b/lib/sqlalchemy/engine/mock.py
index d98d0ee3a..570ee2d04 100644
--- a/lib/sqlalchemy/engine/mock.py
+++ b/lib/sqlalchemy/engine/mock.py
@@ -108,7 +108,7 @@ def create_mock_engine(url, executor, **kw):
     # consume dialect arguments from kwargs
     for k in util.get_cls_kwargs(dialect_cls):
         if k in kw:
-            dialect_args[k] = kwargs.pop(k)
+            dialect_args[k] = kw.pop(k)
 
     # create dialect
     dialect = dialect_cls(**dialect_args)
diff --git a/lib/sqlalchemy/orm/attributes.py b/lib/sqlalchemy/orm/attributes.py
index 1805bf8db..66a18da99 100644
--- a/lib/sqlalchemy/orm/attributes.py
+++ b/lib/sqlalchemy/orm/attributes.py
@@ -1586,10 +1586,8 @@ def backref_listeners(attribute, key, uselist):
 _NO_HISTORY = util.symbol("NO_HISTORY")
 _NO_STATE_SYMBOLS = frozenset([id(PASSIVE_NO_RESULT), id(NO_VALUE)])
 
-History = util.namedtuple("History", ["added", "unchanged", "deleted"])
 
-
-class History(History):
+class History(util.namedtuple("History", ["added", "unchanged", "deleted"])):
     """A 3-tuple of added, unchanged and deleted values,
     representing the changes which have occurred on an instrumented
     attribute.
diff --git a/lib/sqlalchemy/orm/interfaces.py b/lib/sqlalchemy/orm/interfaces.py
index 21479c08b..c7b059fda 100644
--- a/lib/sqlalchemy/orm/interfaces.py
+++ b/lib/sqlalchemy/orm/interfaces.py
@@ -39,6 +39,12 @@ from ..sql import operators
 from ..sql import visitors
 from ..sql.traversals import HasCacheKey
 
+if util.TYPE_CHECKING:
+    from typing import Any
+    from typing import List
+    from typing import Optional
+    from .mapper import Mapper
+    from .util import AliasedInsp
 
 __all__ = (
     "EXT_CONTINUE",
@@ -363,8 +369,12 @@ class PropComparator(operators.ColumnOperators):
 
     __slots__ = "prop", "property", "_parententity", "_adapt_to_entity"
 
-    def __init__(self, prop, parentmapper, adapt_to_entity=None):
-        # type: (MapperProperty, Mapper, Optional(AliasedInsp))
+    def __init__(
+        self,
+        prop,  # type: MapperProperty
+        parentmapper,  # type: Mapper
+        adapt_to_entity=None,  # type: Optional[AliasedInsp]
+    ):
         self.prop = self.property = prop
         self._parententity = adapt_to_entity or parentmapper
         self._adapt_to_entity = adapt_to_entity
@@ -372,8 +382,10 @@ class PropComparator(operators.ColumnOperators):
     def __clause_element__(self):
         raise NotImplementedError("%r" % self)
 
-    def _bulk_update_tuples(self, value):
-        # type: (ColumnOperators) -> List[tuple[ColumnOperators, Any]]
+    def _bulk_update_tuples(
+        self, value  # type: (operators.ColumnOperators)
+    ):
+        # type: (...) -> List[tuple[operators.ColumnOperators, Any]]
         """Receive a SQL expression that represents a value in the SET
         clause of an UPDATE statement.
 
diff --git a/lib/sqlalchemy/orm/relationships.py b/lib/sqlalchemy/orm/relationships.py
index f1764672c..d745500c1 100644
--- a/lib/sqlalchemy/orm/relationships.py
+++ b/lib/sqlalchemy/orm/relationships.py
@@ -50,6 +50,11 @@ from ..sql.util import selectables_overlap
 from ..sql.util import visit_binary_product
 
 
+if util.TYPE_CHECKING:
+    from .util import AliasedInsp
+    from typing import Union
+
+
 def remote(expr):
     """Annotate a portion of a primaryjoin expression
     with a 'remote' annotation.
@@ -1859,9 +1864,9 @@ class RelationshipProperty(StrategizedProperty):
             )
 
     @util.memoized_property
-    def entity(self):  # type: () -> Union[AliasedInsp, Mapper]
+    def entity(self):  # type: () -> Union[AliasedInsp, mapperlib.Mapper]
         """Return the target mapped entity, which is an inspect() of the
-        class or aliased class tha is referred towards.
+        class or aliased class that is referred towards.
 
         """
         if callable(self.argument) and not isinstance(
diff --git a/lib/sqlalchemy/sql/base.py b/lib/sqlalchemy/sql/base.py
index 60456223f..a7324c45f 100644
--- a/lib/sqlalchemy/sql/base.py
+++ b/lib/sqlalchemy/sql/base.py
@@ -19,9 +19,12 @@ from .visitors import ClauseVisitor
 from .. import exc
 from .. import util
 
-coercions = None  # type: types.ModuleType
-elements = None  # type: types.ModuleType
-type_api = None  # type: types.ModuleType
+if util.TYPE_CHECKING:
+    from types import ModuleType
+
+coercions = None  # type: ModuleType
+elements = None  # type: ModuleType
+type_api = None  # type: ModuleType
 
 PARSE_AUTOCOMMIT = util.symbol("PARSE_AUTOCOMMIT")
 NO_ARG = util.symbol("NO_ARG")
diff --git a/lib/sqlalchemy/sql/coercions.py b/lib/sqlalchemy/sql/coercions.py
index 12ec7c750..b3bf4e93b 100644
--- a/lib/sqlalchemy/sql/coercions.py
+++ b/lib/sqlalchemy/sql/coercions.py
@@ -17,10 +17,13 @@ from .. import inspection
 from .. import util
 from ..util import collections_abc
 
-elements = None  # type: types.ModuleType
-schema = None  # type: types.ModuleType
-selectable = None  # type: types.ModuleType
-sqltypes = None  # type: types.ModuleType
+if util.TYPE_CHECKING:
+    from types import ModuleType
+
+elements = None  # type: ModuleType
+schema = None  # type: ModuleType
+selectable = None  # type: ModuleType
+sqltypes = None  # type: ModuleType
 
 
 def _is_literal(element):
diff --git a/lib/sqlalchemy/sql/elements.py b/lib/sqlalchemy/sql/elements.py
index d94d91b16..422eb6220 100644
--- a/lib/sqlalchemy/sql/elements.py
+++ b/lib/sqlalchemy/sql/elements.py
@@ -43,6 +43,11 @@ from .. import exc
 from .. import inspection
 from .. import util
 
+if util.TYPE_CHECKING:
+    from typing import Any
+    from typing import Optional
+    from typing import Union
+
 
 def collate(expression, collation):
     """Return the clause ``expression COLLATE collation``.
@@ -709,7 +714,7 @@ class ColumnElement(
     _alt_names = ()
 
     def self_group(self, against=None):
-        # type: (Module, Module, Optional[Any]) -> ClauseEleent
+        # type: (Optional[Any]) -> ClauseElement
         if (
             against in (operators.and_, operators.or_, operators._asbool)
             and self.type._type_affinity is type_api.BOOLEANTYPE._type_affinity
diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py
index 8f5503db0..136c9f868 100644
--- a/lib/sqlalchemy/sql/selectable.py
+++ b/lib/sqlalchemy/sql/selectable.py
@@ -50,6 +50,10 @@ from .visitors import InternalTraversal
 from .. import exc
 from .. import util
 
+if util.TYPE_CHECKING:
+    from typing import Any
+    from typing import Optional
+
 
 class _OffsetLimitParam(BindParameter):
     @property
@@ -2096,7 +2100,7 @@ class SelectBase(
     _memoized_property = util.group_expirable_memoized_property()
 
     def _generate_fromclause_column_proxies(self, fromclause):
-        # type: (FromClause)
+        # type: (FromClause) -> None
         raise NotImplementedError()
 
     def _refresh_for_new_column(self, column):
@@ -2344,7 +2348,7 @@ class SelectStatementGrouping(GroupedElement, SelectBase):
     _is_select_container = True
 
     def __init__(self, element):
-        # type: (SelectBase)
+        # type: (SelectBase) -> None
         self.element = coercions.expect(roles.SelectStatementRole, element)
 
     @property
diff --git a/lib/sqlalchemy/testing/__init__.py b/lib/sqlalchemy/testing/__init__.py
index e5425dd81..ab1198da8 100644
--- a/lib/sqlalchemy/testing/__init__.py
+++ b/lib/sqlalchemy/testing/__init__.py
@@ -54,6 +54,7 @@ from .util import adict  # noqa
 from .util import fail  # noqa
 from .util import flag_combinations  # noqa
 from .util import force_drop_names  # noqa
+from .util import lambda_combinations  # noqa
 from .util import metadata_fixture  # noqa
 from .util import provide_metadata  # noqa
 from .util import resolve_lambda  # noqa
diff --git a/lib/sqlalchemy/testing/exclusions.py b/lib/sqlalchemy/testing/exclusions.py
index 8b17f64c7..b2828b107 100644
--- a/lib/sqlalchemy/testing/exclusions.py
+++ b/lib/sqlalchemy/testing/exclusions.py
@@ -159,7 +159,9 @@ class compound(object):
         for fail in self.fails:
             if self._check_combinations(combination, fail) and fail(config):
                 if util.py2k:
-                    str_ex = unicode(ex).encode("utf-8", errors="ignore")
+                    str_ex = unicode(ex).encode(  # noqa: F821
+                        "utf-8", errors="ignore"
+                    )
                 else:
                     str_ex = str(ex)
                 print(
diff --git a/lib/sqlalchemy/testing/util.py b/lib/sqlalchemy/testing/util.py
index 74c9b1aeb..de20bb794 100644
--- a/lib/sqlalchemy/testing/util.py
+++ b/lib/sqlalchemy/testing/util.py
@@ -12,13 +12,14 @@ import sys
 import time
 import types
 
+from . import mock
 from ..util import decorator
 from ..util import defaultdict
+from ..util import inspect_getfullargspec
 from ..util import jython
 from ..util import py2k
 from ..util import pypy
 
-
 if jython:
 
     def jython_gc_collect(*args):
@@ -276,6 +277,25 @@ def flag_combinations(*combinations):
     )
 
 
+def lambda_combinations(lambda_arg_sets, **kw):
+    from . import config
+
+    args = inspect_getfullargspec(lambda_arg_sets)
+
+    arg_sets = lambda_arg_sets(*[mock.Mock() for arg in args[0]])
+
+    def create_fixture(pos):
+        def fixture(**kw):
+            return lambda_arg_sets(**kw)[pos]
+
+        fixture.__name__ = "fixture_%3.3d" % pos
+        return fixture
+
+    return config.combinations(
+        *[(create_fixture(i),) for i in range(len(arg_sets))], **kw
+    )
+
+
 def resolve_lambda(__fn, **kw):
     """Given a no-arg lambda and a namespace, return a new lambda that
     has all the values filled in.
@@ -285,10 +305,12 @@ def resolve_lambda(__fn, **kw):
 
     """
 
+    pos_args = inspect_getfullargspec(__fn)[0]
+    pass_pos_args = {arg: kw.pop(arg) for arg in pos_args}
     glb = dict(__fn.__globals__)
     glb.update(kw)
     new_fn = types.FunctionType(__fn.__code__, glb)
-    return new_fn()
+    return new_fn(**pass_pos_args)
 
 
 def metadata_fixture(ddl="function"):
diff --git a/lib/sqlalchemy/util/__init__.py b/lib/sqlalchemy/util/__init__.py
index c1790439c..a19636f62 100644
--- a/lib/sqlalchemy/util/__init__.py
+++ b/lib/sqlalchemy/util/__init__.py
@@ -80,6 +80,7 @@ from .compat import StringIO  # noqa
 from .compat import text_type  # noqa
 from .compat import threading  # noqa
 from .compat import timezone  # noqa
+from .compat import TYPE_CHECKING  # noqa
 from .compat import u  # noqa
 from .compat import ue  # noqa
 from .compat import unquote  # noqa
diff --git a/lib/sqlalchemy/util/compat.py b/lib/sqlalchemy/util/compat.py
index 82bf68d2c..2cb5db5d4 100644
--- a/lib/sqlalchemy/util/compat.py
+++ b/lib/sqlalchemy/util/compat.py
@@ -158,6 +158,8 @@ if py3k:
     def ue(s):
         return s
 
+    from typing import TYPE_CHECKING
+
     # Unused. Kept for backwards compatibility.
     callable = callable  # noqa
 else:
@@ -244,8 +246,10 @@ else:
     def safe_bytestring(text):
         # py2k only
         if not isinstance(text, string_types):
-            return unicode(text).encode("ascii", errors="backslashreplace")
-        elif isinstance(text, unicode):
+            return unicode(text).encode(  # noqa: F821
+                "ascii", errors="backslashreplace"
+            )
+        elif isinstance(text, unicode):  # noqa: F821
             return text.encode("ascii", errors="backslashreplace")
         else:
             return text
@@ -259,6 +263,8 @@ else:
         "    raise tp, value, tb\n"
     )
 
+    TYPE_CHECKING = False
+
 
 if py35:
     from inspect import formatannotation