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, 25 insertions, 13 deletions

diff --git a/lib/sqlalchemy/engine/_py_util.py b/lib/sqlalchemy/engine/_py_util.py
index ff03a4761..538c075a2 100644
--- a/lib/sqlalchemy/engine/_py_util.py
+++ b/lib/sqlalchemy/engine/_py_util.py
@@ -1,21 +1,32 @@
 from __future__ import annotations
 
-from collections import abc as collections_abc
+import typing
+from typing import Any
+from typing import Mapping
+from typing import Optional
+from typing import Tuple
 
 from .. import exc
 
-_no_tuple = ()
+if typing.TYPE_CHECKING:
+    from .interfaces import _CoreAnyExecuteParams
+    from .interfaces import _CoreMultiExecuteParams
+    from .interfaces import _DBAPIAnyExecuteParams
+    from .interfaces import _DBAPIMultiExecuteParams
 
 
-def _distill_params_20(params):
+_no_tuple: Tuple[Any, ...] = ()
+
+
+def _distill_params_20(
+    params: Optional[_CoreAnyExecuteParams],
+) -> _CoreMultiExecuteParams:
     if params is None:
         return _no_tuple
     # Assume list is more likely than tuple
     elif isinstance(params, list) or isinstance(params, tuple):
         # collections_abc.MutableSequence): # avoid abc.__instancecheck__
-        if params and not isinstance(
-            params[0], (tuple, collections_abc.Mapping)
-        ):
+        if params and not isinstance(params[0], (tuple, Mapping)):
             raise exc.ArgumentError(
                 "List argument must consist only of tuples or dictionaries"
             )
@@ -25,21 +36,21 @@ def _distill_params_20(params):
         # only do immutabledict or abc.__instancecheck__ for Mapping after
         # we've checked for plain dictionaries and would otherwise raise
         params,
-        collections_abc.Mapping,
+        Mapping,
     ):
         return [params]
     else:
         raise exc.ArgumentError("mapping or list expected for parameters")
 
 
-def _distill_raw_params(params):
+def _distill_raw_params(
+    params: Optional[_DBAPIAnyExecuteParams],
+) -> _DBAPIMultiExecuteParams:
     if params is None:
         return _no_tuple
     elif isinstance(params, list):
         # collections_abc.MutableSequence): # avoid abc.__instancecheck__
-        if params and not isinstance(
-            params[0], (tuple, collections_abc.Mapping)
-        ):
+        if params and not isinstance(params[0], (tuple, Mapping)):
             raise exc.ArgumentError(
                 "List argument must consist only of tuples or dictionaries"
             )
@@ -49,8 +60,9 @@ def _distill_raw_params(params):
         # only do abc.__instancecheck__ for Mapping after we've checked
         # for plain dictionaries and would otherwise raise
         params,
-        collections_abc.Mapping,
+        Mapping,
     ):
-        return [params]
+        # cast("Union[List[Mapping[str, Any]], Tuple[Any, ...]]", [params])
+        return [params]  # type: ignore
     else:
         raise exc.ArgumentError("mapping or sequence expected for parameters")