39 lines
1.5 KiB
Python
39 lines
1.5 KiB
Python
"""
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This is a Nix-specific module for discovering modules built with Nix.
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The module recursively adds paths that are on `NIX_PYTHONPATH` to `sys.path`. In
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order to process possible `.pth` files `site.addsitedir` is used.
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The paths listed in `PYTHONPATH` are added to `sys.path` afterwards, but they
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will be added before the entries we add here and thus take precedence.
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Note the `NIX_PYTHONPATH` environment variable is unset in order to prevent leakage.
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Similarly, this module listens to the environment variable `NIX_PYTHONEXECUTABLE`
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and sets `sys.executable` to its value.
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"""
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import site
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import sys
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import os
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import functools
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paths = os.environ.pop('NIX_PYTHONPATH', None)
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if paths:
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functools.reduce(lambda k, p: site.addsitedir(p, k), paths.split(':'), site._init_pathinfo())
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# Check whether we are in a venv.
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# Note Python 2 does not support base_prefix so we assume we are not in a venv.
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in_venv = sys.version_info.major == 3 and sys.prefix != sys.base_prefix
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if not in_venv:
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executable = os.environ.pop('NIX_PYTHONEXECUTABLE', None)
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prefix = os.environ.pop('NIX_PYTHONPREFIX', None)
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if 'PYTHONEXECUTABLE' not in os.environ and executable is not None:
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sys.executable = executable
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if prefix is not None:
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# Because we cannot check with Python 2 whether we are in a venv,
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# creating a venv from a Nix env won't work as well with Python 2.
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# Also, note that sysconfig does not like it when sys.prefix is set to None
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sys.prefix = sys.exec_prefix = prefix
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site.PREFIXES.insert(0, prefix)
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