[Python-Dev] PEP: Post import hooks (original) (raw)

Christian Heimes lists at cheimes.de
Thu Jan 10 23:45:41 CET 2008

Phillip J. Eby wrote:

I'm not setting the hooks to Py_None before the hook are called.

Err, make that NOW, not NOT ... stupid typo.

I'm NOW setting the hooks to Py_None before the hooks are called.

That's fine, but here's a different catch: are you iterating over the hooks by taking the length before you start? If so, then hooks that are added while the hooks are being called back, will never get called, because they'll be added to the end of the list (and you'll never reach the end). Make sure there's a test for that case.

it = iter(self.post_import_registry[name]) self.post_import_registry[name] = None for hook in it: hook(module)

peak.util.imports sets to None after callbacks, but it uses regular list iteration, so hooks can be added to the end of the list while the hooks are still being called.

In my version a hook is immediately called when the the registry value is set to None. When a hook is registered for a module during the execution of the callback then the hook is fired directly and not after the existing hooks are called. Is this a problem for you?

module "foo" is loaded: hook1 hook2 -> registers hookX for "foo" hookX is called directly hook3 hook4

An error while running the hooks should also set the hook list to None and discard all the hooks. There isn't any sane way to recover from an error in a post-import hook.

The hooks are set to None even when an exception is raised by a hook.

Christian

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