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