pep-484 for engine

All modules in sqlalchemy.engine are strictly
typed with the exception of cursor, default, and
reflection.  cursor and default pass with non-strict
typing, reflection is waiting on the multi-reflection
refactor.

Behavioral changes:

* create_connect_args() methods return a tuple of list,
  dict, rather than a list of list, dict
* removed allow_chars parameter from
  pyodbc connector ._get_server_version_info()
  method
* the parameter list passed to do_executemany is now
  a list in all cases. previously, this was being run
  through dialect.execute_sequence_format, which
  defaults to tuple and was only intended for individual
  tuple params.
* broke up dialect.dbapi into dialect.import_dbapi
  class method and dialect.dbapi module object.  added
  a deprecation path for legacy dialects.  it's not
  really feasible to type a single attr as a classmethod
  vs. module type.  The "type_compiler" attribute also
  has this problem with greater ability to work around,
  left that one for now.
* lots of constants changing to be Enum, so that we can
  type them.  for fixed tuple-position constants in
  cursor.py / compiler.py (which are used to avoid the
  speed overhead of namedtuple), using Literal[value]
  which seems to work well
* some tightening up in Row regarding __getitem__, which
  we can do since we are on full 2.0 style result use
* altered the set_connection_execution_options and
  set_engine_execution_options event flows so that the
  dictionary of options may be mutated within the event
  hook, where it will then take effect as the actual
  options used.  Previously, changing the dict would
  be silently ignored which seems counter-intuitive
  and not very useful.
* A lot of DefaultDialect/DefaultExecutionContext
  methods and attributes, including underscored ones, move
  to interfaces.  This is not fully ideal as it means
  the Dialect/ExecutionContext interfaces aren't publicly
  subclassable directly, but their current purpose
  is more of documentation for dialect authors who should
  (and certainly are) still be subclassing the DefaultXYZ
  versions in all cases

Overall, Result was the most extremely difficult class
hierarchy to type here as this hierarchy passes through
largely amorphous "row" datatypes throughout, which
can in fact by all kinds of different things, like
raw DBAPI rows, or Row objects, or "scalar"/Any, but
at the same time these types have meaning so I tried still
maintaining some level of semantic markings for these,
it highlights how complex Result is now, as it's trying
to be extremely efficient and inlined while also being
very open-ended and extensible.

Change-Id: I98b75c0c09eab5355fc7a33ba41dd9874274f12a

1 files changed, 39 insertions, 16 deletions

diff --git a/lib/sqlalchemy/engine/util.py b/lib/sqlalchemy/engine/util.py
index f9ee65bef..213485cc9 100644
--- a/lib/sqlalchemy/engine/util.py
+++ b/lib/sqlalchemy/engine/util.py
@@ -7,18 +7,30 @@
 
 from __future__ import annotations
 
+import typing
+from typing import Any
+from typing import Callable
+from typing import TypeVar
+
 from .. import exc
 from .. import util
+from ..util._has_cy import HAS_CYEXTENSION
+
+if typing.TYPE_CHECKING or not HAS_CYEXTENSION:
+    from ._py_util import _distill_params_20 as _distill_params_20
+    from ._py_util import _distill_raw_params as _distill_raw_params
+else:
+    from sqlalchemy.cyextension.util import (
+        _distill_params_20 as _distill_params_20,
+    )
+    from sqlalchemy.cyextension.util import (
+        _distill_raw_params as _distill_raw_params,
+    )
 
-try:
-    from sqlalchemy.cyextension.util import _distill_params_20  # noqa
-    from sqlalchemy.cyextension.util import _distill_raw_params  # noqa
-except ImportError:
-    from ._py_util import _distill_params_20  # noqa
-    from ._py_util import _distill_raw_params  # noqa
+_C = TypeVar("_C", bound=Callable[[], Any])
 
 
-def connection_memoize(key):
+def connection_memoize(key: str) -> Callable[[_C], _C]:
     """Decorator, memoize a function in a connection.info stash.
 
     Only applicable to functions which take no arguments other than a
@@ -26,7 +38,7 @@ def connection_memoize(key):
     """
 
     @util.decorator
-    def decorated(fn, self, connection):
+    def decorated(fn, self, connection):  # type: ignore
         connection = connection.connect()
         try:
             return connection.info[key]
@@ -34,7 +46,7 @@ def connection_memoize(key):
             connection.info[key] = val = fn(self, connection)
             return val
 
-    return decorated
+    return decorated  # type: ignore[return-value]
 
 
 class TransactionalContext:
@@ -47,13 +59,13 @@ class TransactionalContext:
 
     __slots__ = ("_outer_trans_ctx", "_trans_subject", "__weakref__")
 
-    def _transaction_is_active(self):
+    def _transaction_is_active(self) -> bool:
         raise NotImplementedError()
 
-    def _transaction_is_closed(self):
+    def _transaction_is_closed(self) -> bool:
         raise NotImplementedError()
 
-    def _rollback_can_be_called(self):
+    def _rollback_can_be_called(self) -> bool:
         """indicates the object is in a state that is known to be acceptable
         for rollback() to be called.
 
@@ -70,11 +82,20 @@ class TransactionalContext:
         """
         raise NotImplementedError()
 
-    def _get_subject(self):
+    def _get_subject(self) -> Any:
+        raise NotImplementedError()
+
+    def commit(self) -> None:
+        raise NotImplementedError()
+
+    def rollback(self) -> None:
+        raise NotImplementedError()
+
+    def close(self) -> None:
         raise NotImplementedError()
 
     @classmethod
-    def _trans_ctx_check(cls, subject):
+    def _trans_ctx_check(cls, subject: Any) -> None:
         trans_context = subject._trans_context_manager
         if trans_context:
             if not trans_context._transaction_is_active():
@@ -84,7 +105,7 @@ class TransactionalContext:
                     "before emitting further commands."
                 )
 
-    def __enter__(self):
+    def __enter__(self) -> TransactionalContext:
         subject = self._get_subject()
 
         # none for outer transaction, may be non-None for nested
@@ -96,7 +117,7 @@ class TransactionalContext:
         subject._trans_context_manager = self
         return self
 
-    def __exit__(self, type_, value, traceback):
+    def __exit__(self, type_: Any, value: Any, traceback: Any) -> None:
         subject = getattr(self, "_trans_subject", None)
 
         # simplistically we could assume that
@@ -119,6 +140,7 @@ class TransactionalContext:
                         self.rollback()
             finally:
                 if not out_of_band_exit:
+                    assert subject is not None
                     subject._trans_context_manager = self._outer_trans_ctx
                 self._trans_subject = self._outer_trans_ctx = None
         else:
@@ -131,5 +153,6 @@ class TransactionalContext:
                         self.rollback()
             finally:
                 if not out_of_band_exit:
+                    assert subject is not None
                     subject._trans_context_manager = self._outer_trans_ctx
                 self._trans_subject = self._outer_trans_ctx = None