M.-A. Lemburg wrote: [msg 1]
Currently, the imputil apporach uses a simple chaining technique. Unfortunately, it doesn't allow inspecting the chain for already loaded hooks, so the same type of hook could be loaded more than once.
I was hoping Greg would jump in, but since he hasn't -
You're associating the hook with the strategy. That's the old style. The imputil style is to associate the hook with the actual stuff being managed. The strategy is a property of the hook.
Also, there are at least two types of hooks:
hooks that redirect the import to some other data source
hooks that modify the way modules are searched
Since the first variant may well also be suited to used by the second, the simple chaining method probably won't be powerful enough to handle it.
The top level question is "is it mine to import?". Greg provides a framework that makes it easy to use alternate data sources, and alternate ways of finding things but that's not really the key thing. You're a "good" importer if you can (when appropriate) way "no it's not mine" efficiently. [msg 2]
Another quirk that I think needs fixing:
When I issues an import:
the whole import is handled by the importer installed at the start of the import. It is not possible to install a different importer e.g. in mx/__init__.py to handle the rest of the import (in this case the import of subpackage DateTime). I think that the importer should honor the __importer__ function (this is set by imputil) if present to let it continue the import of subsequent elements in the dotted name.
Sure you can. Your first importer is the "mx" importer. It has a dict of sub-importers. When mx/DateTime/__init__.py runs, it puts itself into that dict. The importer chain is now a tree.
This means, I think, that a "general" relative-path importer (ie, one that uses the default PYTHONPATH strategy), should be careful to install itself as the penultimate importer in the chain, (ie, the last before __builtin__.imp). But putting a relative-path search strategy into the "mx" importer is fine if it can quickly determine that the target is / is not a valid name in the "mx" namespace.