| 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 |
| # mysterious hack: |
| # Remove the reference to the extant package/module |
| # on later Python versions to cause relative imports |
| # in the vendor package to resolve the same modules |
| # as those going through this importer. |
| if sys.version_info > (3, 3): |
| del sys.modules[extant] |
| 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', 'six', 'appdirs' |
| VendorImporter(__name__, names).install() |
