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74 lines
2.3 KiB
Python
74 lines
2.3 KiB
Python
2 years ago
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import importlib.util
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import sys
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class VendorImporter:
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"""
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A PEP 302 meta path importer for finding optionally-vendored
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or otherwise naturally-installed packages from root_name.
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"""
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def __init__(self, root_name, vendored_names=(), vendor_pkg=None):
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self.root_name = root_name
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self.vendored_names = set(vendored_names)
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self.vendor_pkg = vendor_pkg or root_name.replace('extern', '_vendor')
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@property
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def search_path(self):
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"""
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Search first the vendor package then as a natural package.
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"""
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yield self.vendor_pkg + '.'
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yield ''
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def _module_matches_namespace(self, fullname):
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"""Figure out if the target module is vendored."""
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root, base, target = fullname.partition(self.root_name + '.')
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return not root and any(map(target.startswith, self.vendored_names))
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def load_module(self, fullname):
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"""
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Iterate over the search path to locate and load fullname.
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"""
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root, base, target = fullname.partition(self.root_name + '.')
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for prefix in self.search_path:
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try:
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extant = prefix + target
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__import__(extant)
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mod = sys.modules[extant]
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sys.modules[fullname] = mod
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return mod
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except ImportError:
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pass
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else:
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raise ImportError(
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"The '{target}' package is required; "
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"normally this is bundled with this package so if you get "
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"this warning, consult the packager of your "
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"distribution.".format(**locals())
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)
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def create_module(self, spec):
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return self.load_module(spec.name)
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def exec_module(self, module):
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pass
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def find_spec(self, fullname, path=None, target=None):
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"""Return a module spec for vendored names."""
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return (
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importlib.util.spec_from_loader(fullname, self)
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if self._module_matches_namespace(fullname) else None
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)
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def install(self):
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"""
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Install this importer into sys.meta_path if not already present.
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"""
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if self not in sys.meta_path:
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sys.meta_path.append(self)
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names = 'packaging', 'pyparsing', 'appdirs'
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VendorImporter(__name__, names).install()
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