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venv/lib/python3.9/site-packages/mlflow/utils/import_hooks/__init__.py

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+"""
+NOTE: The contents of this file have been inlined from the wrapt package's source code
+https://github.com/GrahamDumpleton/wrapt/blob/1.12.1/src/wrapt/importer.py.
+Some modifications, have been made in order to:
+    - avoid duplicate registration of import hooks
+    - inline functions from dependent wrapt submodules rather than importing them.
+
+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.
+It also extends the functionality to support custom hooks for import errors
+(as opposed to only successful imports).
+"""
+
+import importlib  # noqa: F401
+import sys
+import threading
+
+string_types = (str,)
+
+
+# from .decorators import synchronized
+# NOTE: Instead of using this import (from wrapt's decorator module, see
+# https://github.com/GrahamDumpleton/wrapt/blob/68316bea668fd905a4acb21f37f12596d8c30d80/src/wrapt/decorators.py#L430-L456),
+# we define a decorator with similar behavior that acquires a lock while calling the decorated
+# function
+def synchronized(lock):
+    def decorator(f):
+        # See e.g. https://www.python.org/dev/peps/pep-0318/#examples
+        def new_fn(*args, **kwargs):
+            with lock:
+                return f(*args, **kwargs)
+
+        return new_fn
+
+    return decorator
+
+
+# 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 truncated 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_lock = threading.RLock()
+
+# A dictionary for any import hook error handlers to be triggered when the
+# target module import fails.
+
+_import_error_hooks = {}
+_import_error_hooks_lock = threading.RLock()
+
+_import_hook_finder_init = False
+
+# 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
+
+
+def register_generic_import_hook(hook, name, hook_dict, overwrite):
+    # 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 _import_hook_finder_init
+    if not _import_hook_finder_init:
+        _import_hook_finder_init = True
+        sys.meta_path.insert(0, ImportHookFinder())
+
+    # Determine if any prior registration of an import hook for
+    # the target modules has occurred and act appropriately.
+
+    hooks = hook_dict.get(name, None)
+
+    if hooks is None:
+        # No prior registration of 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:
+            hook_dict[name] = []
+            hook(module)
+
+        else:
+            hook_dict[name] = [hook]
+
+    elif hooks == []:
+        # A prior registration of 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 import hooks for the target
+        # module was done but the module has not yet been imported.
+
+        def hooks_equal(existing_hook, hook):
+            if hasattr(existing_hook, "__name__") and hasattr(hook, "__name__"):
+                return existing_hook.__name__ == hook.__name__
+            else:
+                return False
+
+        if overwrite:
+            hook_dict[name] = [
+                existing_hook
+                for existing_hook in hook_dict[name]
+                if not hooks_equal(existing_hook, hook)
+            ]
+
+        hook_dict[name].append(hook)
+
+
+@synchronized(_import_error_hooks_lock)
+def register_import_error_hook(hook, name, overwrite=True):
+    """
+    Args:
+        hook: A function or string entrypoint to invoke when the specified module is imported
+            and an error occurs.
+        name: The name of the module for which to fire the hook at import error detection time.
+        overwrite: Specifies the desired behavior when a preexisting hook for the same
+            function / entrypoint already exists for the specified module. If `True`,
+            all preexisting hooks matching the specified function / entrypoint will be
+            removed and replaced with a single instance of the specified `hook`.
+    """
+    register_generic_import_hook(hook, name, _import_error_hooks, overwrite)
+
+
+@synchronized(_post_import_hooks_lock)
+def register_post_import_hook(hook, name, overwrite=True):
+    """
+    Args:
+        hook: A function or string entrypoint to invoke when the specified module is imported.
+        name: The name of the module for which to fire the hook at import time.
+        overwrite: Specifies the desired behavior when a preexisting hook for the same
+            function / entrypoint already exists for the specified module. If `True`,
+            all preexisting hooks matching the specified function / entrypoint will be
+            removed and replaced with a single instance of the specified `hook`.
+    """
+    register_generic_import_hook(hook, name, _post_import_hooks, overwrite)
+
+
+@synchronized(_post_import_hooks_lock)
+def get_post_import_hooks(name):
+    return _post_import_hooks.get(name)
+
+
+# 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):
+    # New in 3.9: https://docs.python.org/3/library/importlib.resources.html#importlib.resources.files
+    if sys.version_info.major > 2 and sys.version_info.minor > 8:
+        from importlib.resources import files  # clint: disable=lazy-builtin-import
+
+        for entrypoint in (
+            resource.name for resource in files(group).iterdir() if resource.is_file()
+        ):
+            callback = _create_import_hook_from_entrypoint(entrypoint)
+            register_post_import_hook(callback, entrypoint.name)
+    else:
+        from importlib.resources import contents  # clint: disable=lazy-builtin-import
+
+        for entrypoint in contents(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)
+
+    if hooks:
+        _post_import_hooks[name] = []
+
+        for hook in hooks:
+            hook(module)
+
+
+@synchronized(_import_error_hooks_lock)
+def notify_module_import_error(module_name):
+    hooks = _import_error_hooks.get(module_name)
+
+    if hooks:
+        # Error hooks differ from post import hooks, in that we don't clear the
+        # hook as soon as it fires.
+        for hook in hooks:
+            hook(module_name)
+
+
+# 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 _ImportHookChainedLoader:
+    def __init__(self, loader):
+        self.loader = loader
+
+    def load_module(self, fullname):
+        try:
+            module = self.loader.load_module(fullname)
+            notify_module_loaded(module)
+        except (ImportError, AttributeError):
+            notify_module_import_error(fullname)
+            raise
+
+        return module
+
+
+class ImportHookFinder:
+    def __init__(self):
+        self.in_progress = {}
+
+    @synchronized(_post_import_hooks_lock)
+    @synchronized(_import_error_hooks_lock)
+    def find_module(self, fullname, path=None):
+        # If the module being imported is not one we have registered
+        # import hooks for, we can return immediately. We will
+        # take no further part in the importing of this module.
+
+        if fullname not in _post_import_hooks and fullname not in _import_error_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:
+            # 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  # clint: disable=lazy-builtin-import
+
+                loader = importlib.util.find_spec(fullname).loader
+            # If an ImportError (or AttributeError) is encountered while finding the module,
+            # notify the hooks for import errors
+            except (ImportError, AttributeError):
+                notify_module_import_error(fullname)
+                loader = importlib.find_loader(fullname, path)
+            if loader:
+                return _ImportHookChainedLoader(loader)
+        finally:
+            del self.in_progress[fullname]
+
+    @synchronized(_post_import_hooks_lock)
+    @synchronized(_import_error_hooks_lock)
+    def find_spec(self, fullname, path, target=None):
+        # If the module being imported is not one we have registered
+        # import hooks for, we can return immediately. We will
+        # take no further part in the importing of this module.
+
+        if fullname not in _post_import_hooks and fullname not in _import_error_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:
+            import importlib.util  # clint: disable=lazy-builtin-import
+
+            spec = importlib.util.find_spec(fullname)
+            # Replace the module spec's loader with a wrapped version that executes import
+            # hooks when the module is loaded
+            spec.loader = _ImportHookChainedLoader(spec.loader)
+            return spec
+        except (ImportError, AttributeError):
+            notify_module_import_error(fullname)
+        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.
+# If error_handler is True, then apply the marked function as an import hook
+# for import errors (instead of successful imports).
+# It is assumed that all error hooks are added during driver start-up,
+# and thus added prior to any import calls. If an error hook is added
+# after a module has already failed the import, there's no guarantee
+# that the hook will fire.
+
+
+def when_imported(name, error_handler=False):
+    def register(hook):
+        if error_handler:
+            register_import_error_hook(hook, name)
+        else:
+            register_post_import_hook(hook, name)
+        return hook
+
+    return register