4fbffcd144
There are type annotations that indirectly depend on the typing_extensions module (on Python 3.5-3.7: Protocol was added to the core typing module in 3.8). The typing_extensions module is not installed by default, so the code didn't run on a pristine Python installation. To avoid depending on a non-default module, make the dependency on typing_extensions optional. (It's still required to run mypy, but installing mypy takes care of providing typing_extensions.) If it isn't available, provide a substitute definition that's just good enough to get the scripts to run. Move this ugly code to its own module to avoid the temptation of spreading such ugliness all over the place. It's likely to be used in other modules anyway. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
40 lines
1.5 KiB
Python
40 lines
1.5 KiB
Python
"""Auxiliary definitions used in type annotations.
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"""
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# Copyright The Mbed TLS Contributors
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# SPDX-License-Identifier: Apache-2.0
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from typing import Any
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# The typing_extensions module is necessary for type annotations that are
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# checked with mypy. It is only used for type annotations or to define
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# things that are themselves only used for type annotations. It is not
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# available on a default Python installation. Therefore, try loading
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# what we need from it for the sake of mypy (which depends on, or comes
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# with, typing_extensions), and if not define substitutes that lack the
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# static type information but are good enough at runtime.
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try:
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from typing_extensions import Protocol #pylint: disable=import-error
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except ImportError:
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class Protocol: #type: ignore
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#pylint: disable=too-few-public-methods
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pass
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class Writable(Protocol):
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"""Abstract class for typing hints."""
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# pylint: disable=no-self-use,too-few-public-methods,unused-argument
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def write(self, text: str) -> Any:
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...
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