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| import importlib.util | |
| 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') | |
| def search_path(self): | |
| """ | |
| Search first the vendor package then as a natural package. | |
| """ | |
| yield self.vendor_pkg + '.' | |
| yield '' | |
| def _module_matches_namespace(self, fullname): | |
| """Figure out if the target module is vendored.""" | |
| root, base, target = fullname.partition(self.root_name + '.') | |
| return not root and any(map(target.startswith, self.vendored_names)) | |
| 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 create_module(self, spec): | |
| return self.load_module(spec.name) | |
| def exec_module(self, module): | |
| pass | |
| def find_spec(self, fullname, path=None, target=None): | |
| """Return a module spec for vendored names.""" | |
| return ( | |
| importlib.util.spec_from_loader(fullname, self) | |
| if self._module_matches_namespace(fullname) | |
| else None | |
| ) | |
| 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', | |
| 'platformdirs', | |
| 'jaraco', | |
| 'importlib_resources', | |
| 'more_itertools', | |
| ) | |
| VendorImporter(__name__, names).install() | |