67 lines
2 KiB
Python
67 lines
2 KiB
Python
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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 find_module(self, fullname, path=None):
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"""
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Return self when fullname starts with root_name and the
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target module is one vendored through this importer.
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"""
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root, base, target = fullname.partition(self.root_name + '.')
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if root:
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return
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if not any(map(target.startswith, self.vendored_names)):
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return
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return self
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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 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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