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interfaces: introduce and use a protocol class for the `bdiff` module...
interfaces: introduce and use a protocol class for the `bdiff` module This is allowed by PEP 544[1], and we basically follow the example there. The class here is copied from `mercurial.pure.bdiff`, and the implementation removed. There are several modules that have a few different implementations, and the implementation chosen is controlled by `HGMODULEPOLICY`. The module is loaded via `mercurial/policy.py`, and has been inferred by pytype as `Any` up to this point. Therefore it and PyCharm were blind to all functions on the module, and their signatures. Also, having multiple instances of the same module allows their signatures to get out of sync. Introducing a protocol class allows the loaded module that is stored in a variable to be given type info, which cascades through the various places it is used. This change alters 11 *.pyi files, for example. In theory, this would also allow us to ensure the various implementations of the same module are kept in alignment- simply import the module in a test module, attempt to pass it to a function that uses the corresponding protocol as an argument, and run pytype on it. In practice, this doesn't work (yet). PyCharm (erroneously) flags imported modules being passed where a protocol class is used[2]. Pytype has problems the other way- it fails to detect when a module that doesn't adhere to the protocol is passed to a protocol argument. The good news is that mypy properly detects this case. The bad news is that mypy spews a bunch of other errors when importing even simple modules, like the various `bdiff` modules. Therefore I'm punting on the tests for now because the type info around a loaded module in PyCharm is a clear win by itself. [1] https://peps.python.org/pep-0544/#modules-as-implementations-of-protocols [2] https://youtrack.jetbrains.com/issue/PY-58679/Support-modules-implementing-protocols

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__init__.py
93 lines | 3.0 KiB | text/x-python | PythonLexer
##############################################################################
#
# Copyright (c) 2001, 2002 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""Interfaces
This package implements the Python "scarecrow" proposal.
The package exports two objects, `Interface` and `Attribute` directly. It also
exports several helper methods. Interface is used to create an interface with
a class statement, as in:
class IMyInterface(Interface):
'''Interface documentation
'''
def meth(arg1, arg2):
'''Documentation for meth
'''
# Note that there is no self argument
To find out what you can do with interfaces, see the interface
interface, `IInterface` in the `interfaces` module.
The package has several public modules:
o `declarations` provides utilities to declare interfaces on objects. It
also provides a wide range of helpful utilities that aid in managing
declared interfaces. Most of its public names are however imported here.
o `document` has a utility for documenting an interface as structured text.
o `exceptions` has the interface-defined exceptions
o `interfaces` contains a list of all public interfaces for this package.
o `verify` has utilities for verifying implementations of interfaces.
See the module doc strings for more information.
"""
from __future__ import absolute_import
__docformat__ = 'restructuredtext'
from .interface import Interface
from .interface import _wire
# Need to actually get the interface elements to implement the right interfaces
_wire()
del _wire
from .declarations import Declaration
from .declarations import alsoProvides
from .declarations import classImplements
from .declarations import classImplementsOnly
from .declarations import classProvides
from .declarations import directlyProvidedBy
from .declarations import directlyProvides
from .declarations import implementedBy
from .declarations import implementer
from .declarations import implementer_only
from .declarations import implements
from .declarations import implementsOnly
from .declarations import moduleProvides
from .declarations import named
from .declarations import noLongerProvides
from .declarations import providedBy
from .declarations import provider
from .exceptions import Invalid
from .interface import Attribute
from .interface import invariant
from .interface import taggedValue
# The following are to make spec pickles cleaner
from .declarations import Provides
from .interfaces import IInterfaceDeclaration
moduleProvides(IInterfaceDeclaration)
__all__ = ('Interface', 'Attribute') + tuple(IInterfaceDeclaration)