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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 = 'six', 'packaging', 'pyparsing', 'ordered_set', |
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VendorImporter(__name__, names, 'setuptools._vendor').install() |
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