loader: attempt to fix compatibility with importlib's LazyLoader #7657
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Add the prefix to FrozenImporter to distinguish it from built-in FrozenImporter(s), such as the one from `_importlib_frozen˙.
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Use official importlib.util.LazyLoader example to create tests with lazy import of: - a stdlib module - a 3rd party module with alias, using original name - a 3rd party module with alias, using the alias
Our `PyiFrozenImporter.find_spec` implementation uses `ModuleSpec.loader_state` to store the original entry name under which the module can be found within the PYZ archive. The `PyiFrozenImporter.exec_module` then uses this information to retrieve the module's code object from the PYZ archive, even if the module's name (in `ModuleSpec.name`) is changed. However, it seems that when using `importlib.util.LazyLoader`, `PyiFrozenImporer.exec_module` gets called with module object whose spec contains modified `loader_state`. Therefore, have our `find_spec` use a custom object type for `loader_state`; this allows `exec_module` to always determine whether the `loader_state` came from our `find_spec` or not. For now, in the latter case we raise an error.
When `importlib.util.LazyLoader` is used, the `module` passed to the `PyiFrozenImporter.exec_module` contains modified spec, in which the `loader_state` is a `dict` prepared by the `LazyLoader` code. This means that our original `loader_state` is lost, and we need to determine the module name for look-up in the PYZ by other means. Specifically, we convert the `origin` back to the module name, which allows us to handle aliased modules as well.
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bwoodsend
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May 24, 2023
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When a module is lazily imported using
importlib.util.LazyLoader, the module's spec is modified and theloader_statemember is overwritten with a dictionary constructed by theLazyLoader's code. Unfortunately, this breaks our frozen importer, because ourfind_specimplementation uses that field to store the PYZ entry name, andexec_modulereads it before trying to look-up the code object in the PYZ. (And this seems to be necessary to handle aliased modules, such aspkg_resources._vendor.jaraco.textbeing aliased aspkg_resources.extern.jaraco.text).See for an example in the wild: #7655 (comment)