105 lines
4.2 KiB
Python
105 lines
4.2 KiB
Python
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# MIT License
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#
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# Copyright The SCons Foundation
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#
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# Permission is hereby granted, free of charge, to any person obtaining
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# a copy of this software and associated documentation files (the
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# "Software"), to deal in the Software without restriction, including
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# without limitation the rights to use, copy, modify, merge, publish,
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# distribute, sublicense, and/or sell copies of the Software, and to
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# permit persons to whom the Software is furnished to do so, subject to
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# the following conditions:
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#
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# The above copyright notice and this permission notice shall be included
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# in all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
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# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
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# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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"""SCons compatibility package for old Python versions
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This subpackage holds modules that provide backwards-compatible
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implementations of various things from newer Python versions
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that we cannot count on because SCons still supported older Pythons.
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Other code will not generally reference things in this package through
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the SCons.compat namespace. The modules included here add things to
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the builtins namespace or the global module list so that the rest
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of our code can use the objects and names imported here regardless of
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Python version. As a result, if this module is used, it should violate
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the normal convention for imports (standard library imports first,
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then program-specific imports, each ordered aplhabetically)
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and needs to be listed first.
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The rest of the things here will be in individual compatibility modules
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that are either: 1) suitably modified copies of the future modules that
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we want to use; or 2) backwards compatible re-implementations of the
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specific portions of a future module's API that we want to use.
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GENERAL WARNINGS: Implementations of functions in the SCons.compat
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modules are *NOT* guaranteed to be fully compliant with these functions in
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later versions of Python. We are only concerned with adding functionality
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that we actually use in SCons, so be wary if you lift this code for
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other uses. (That said, making these more nearly the same as later,
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official versions is still a desirable goal, we just don't need to be
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obsessive about it.)
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We name the compatibility modules with an initial '_scons_' (for example,
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_scons_subprocess.py is our compatibility module for subprocess) so
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that we can still try to import the real module name and fall back to
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our compatibility module if we get an ImportError. The import_as()
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function defined below loads the module as the "real" name (without the
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'_scons'), after which all of the "import {module}" statements in the
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rest of our code will find our pre-loaded compatibility module.
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"""
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import sys
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import importlib
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PYPY = hasattr(sys, 'pypy_translation_info')
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def rename_module(new, old):
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"""
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Attempt to import the old module and load it under the new name.
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Used for purely cosmetic name changes in Python 3.x.
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"""
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try:
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sys.modules[new] = importlib.import_module(old)
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return True
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except ImportError:
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return False
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# Default pickle protocol. Higher protocols are more efficient/featured
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# but incompatible with older Python versions.
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# Negative numbers choose the highest available protocol.
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# Was pickle.HIGHEST_PROTOCOL
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# Changed to 4 so that python 3.8's not incompatible with previous versions
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# Python 3.8 introduced protocol 5 which is mainly an improvement for for out-of-band data buffers
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PICKLE_PROTOCOL = 4
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class NoSlotsPyPy(type):
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""" Metaclass for PyPy compatitbility.
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PyPy does not work well with __slots__ and __class__ assignment.
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"""
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def __new__(meta, name, bases, dct):
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if PYPY and '__slots__' in dct:
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dct.pop('__slots__')
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return super(NoSlotsPyPy, meta).__new__(meta, name, bases, dct)
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# Local Variables:
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# tab-width:4
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# indent-tabs-mode:nil
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# End:
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# vim: set expandtab tabstop=4 shiftwidth=4:
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