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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 = ( |
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'packaging', 'pyparsing', 'appdirs', 'jaraco', 'importlib_resources', |
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'more_itertools', |
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) |
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VendorImporter(__name__, names).install() |
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