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Diffstat (limited to 'venv/Lib/site-packages/wrapt/importer.py')
| -rw-r--r-- | venv/Lib/site-packages/wrapt/importer.py | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/venv/Lib/site-packages/wrapt/importer.py b/venv/Lib/site-packages/wrapt/importer.py new file mode 100644 index 0000000..9e617cd --- /dev/null +++ b/venv/Lib/site-packages/wrapt/importer.py @@ -0,0 +1,230 @@ +"""This module implements a post import hook mechanism styled after what is +described in PEP-369. Note that it doesn't cope with modules being reloaded. + +""" + +import sys +import threading + +PY2 = sys.version_info[0] == 2 +PY3 = sys.version_info[0] == 3 + +if PY3: + import importlib + string_types = str, +else: + string_types = basestring, + +from .decorators import synchronized + +# The dictionary registering any post import hooks to be triggered once +# the target module has been imported. Once a module has been imported +# and the hooks fired, the list of hooks recorded against the target +# module will be truncacted but the list left in the dictionary. This +# acts as a flag to indicate that the module had already been imported. + +_post_import_hooks = {} +_post_import_hooks_init = False +_post_import_hooks_lock = threading.RLock() + +# Register a new post import hook for the target module name. This +# differs from the PEP-369 implementation in that it also allows the +# hook function to be specified as a string consisting of the name of +# the callback in the form 'module:function'. This will result in a +# proxy callback being registered which will defer loading of the +# specified module containing the callback function until required. + +def _create_import_hook_from_string(name): + def import_hook(module): + module_name, function = name.split(':') + attrs = function.split('.') + __import__(module_name) + callback = sys.modules[module_name] + for attr in attrs: + callback = getattr(callback, attr) + return callback(module) + return import_hook + +@synchronized(_post_import_hooks_lock) +def register_post_import_hook(hook, name): + # Create a deferred import hook if hook is a string name rather than + # a callable function. + + if isinstance(hook, string_types): + hook = _create_import_hook_from_string(hook) + + # Automatically install the import hook finder if it has not already + # been installed. + + global _post_import_hooks_init + + if not _post_import_hooks_init: + _post_import_hooks_init = True + sys.meta_path.insert(0, ImportHookFinder()) + + # Determine if any prior registration of a post import hook for + # the target modules has occurred and act appropriately. + + hooks = _post_import_hooks.get(name, None) + + if hooks is None: + # No prior registration of post import hooks for the target + # module. We need to check whether the module has already been + # imported. If it has we fire the hook immediately and add an + # empty list to the registry to indicate that the module has + # already been imported and hooks have fired. Otherwise add + # the post import hook to the registry. + + module = sys.modules.get(name, None) + + if module is not None: + _post_import_hooks[name] = [] + hook(module) + + else: + _post_import_hooks[name] = [hook] + + elif hooks == []: + # A prior registration of port import hooks for the target + # module was done and the hooks already fired. Fire the hook + # immediately. + + module = sys.modules[name] + hook(module) + + else: + # A prior registration of port import hooks for the target + # module was done but the module has not yet been imported. + + _post_import_hooks[name].append(hook) + +# Register post import hooks defined as package entry points. + +def _create_import_hook_from_entrypoint(entrypoint): + def import_hook(module): + __import__(entrypoint.module_name) + callback = sys.modules[entrypoint.module_name] + for attr in entrypoint.attrs: + callback = getattr(callback, attr) + return callback(module) + return import_hook + +def discover_post_import_hooks(group): + try: + import pkg_resources + except ImportError: + return + + for entrypoint in pkg_resources.iter_entry_points(group=group): + callback = _create_import_hook_from_entrypoint(entrypoint) + register_post_import_hook(callback, entrypoint.name) + +# Indicate that a module has been loaded. Any post import hooks which +# were registered against the target module will be invoked. If an +# exception is raised in any of the post import hooks, that will cause +# the import of the target module to fail. + +@synchronized(_post_import_hooks_lock) +def notify_module_loaded(module): + name = getattr(module, '__name__', None) + hooks = _post_import_hooks.get(name, None) + + if hooks: + _post_import_hooks[name] = [] + + for hook in hooks: + hook(module) + +# A custom module import finder. This intercepts attempts to import +# modules and watches out for attempts to import target modules of +# interest. When a module of interest is imported, then any post import +# hooks which are registered will be invoked. + +class _ImportHookLoader: + + def load_module(self, fullname): + module = sys.modules[fullname] + notify_module_loaded(module) + + return module + +class _ImportHookChainedLoader: + + def __init__(self, loader): + self.loader = loader + + def load_module(self, fullname): + module = self.loader.load_module(fullname) + notify_module_loaded(module) + + return module + +class ImportHookFinder: + + def __init__(self): + self.in_progress = {} + + @synchronized(_post_import_hooks_lock) + def find_module(self, fullname, path=None): + # If the module being imported is not one we have registered + # post import hooks for, we can return immediately. We will + # take no further part in the importing of this module. + + if not fullname in _post_import_hooks: + return None + + # When we are interested in a specific module, we will call back + # into the import system a second time to defer to the import + # finder that is supposed to handle the importing of the module. + # We set an in progress flag for the target module so that on + # the second time through we don't trigger another call back + # into the import system and cause a infinite loop. + + if fullname in self.in_progress: + return None + + self.in_progress[fullname] = True + + # Now call back into the import system again. + + try: + if PY3: + # For Python 3 we need to use find_spec().loader + # from the importlib.util module. It doesn't actually + # import the target module and only finds the + # loader. If a loader is found, we need to return + # our own loader which will then in turn call the + # real loader to import the module and invoke the + # post import hooks. + try: + import importlib.util + loader = importlib.util.find_spec(fullname).loader + except (ImportError, AttributeError): + loader = importlib.find_loader(fullname, path) + if loader: + return _ImportHookChainedLoader(loader) + + else: + # For Python 2 we don't have much choice but to + # call back in to __import__(). This will + # actually cause the module to be imported. If no + # module could be found then ImportError will be + # raised. Otherwise we return a loader which + # returns the already loaded module and invokes + # the post import hooks. + + __import__(fullname) + + return _ImportHookLoader() + + finally: + del self.in_progress[fullname] + +# Decorator for marking that a function should be called as a post +# import hook when the target module is imported. + +def when_imported(name): + def register(hook): + register_post_import_hook(hook, name) + return hook + return register |