On Tue, Oct 29, 2013 at 7:29 PM, Nick Coghlan <ncogh...@gmail.com> wrote: > OK, time for me to stop trying to remember the details of the problem > I'm trying to solve and go look them up in the source code :) > > One of my goals here is to be able to migrate extension loading from > the old API to the new plugin API. That means being able to break up > the existing load_module implementation: > > http://hg.python.org/cpython/file/1787277915e9/Python/importdl.c#l23 > > For loading, that's a fairly straightforward create_module/exec_module > split, but reloading gets a bit more interesting. > > Specifically, I'd like to be able to implement the relevant parts of > _PyImport_FindExtensionObject as a precheck for reloading: > > http://hg.python.org/cpython/file/1787277915e9/Python/import.c#l533 > > That means just having access to the module name isn't enough: the > extensions dictionary is keyed by a (name, filename) 2-tuple rather > than just by the module name. Using the find_spec API, that filename > would be stored in the loader state on the spec object rather than > being looked up anew during the load operation. > > However, rereading this method also indicates that I really want to > know *in exec_module* whether this is a reload or not, since extension > loading needs to handle reloads differently from initial execution. > > So I'm back to my original preference: I'd like the previous spec to > be passed to exec_module in the reloading case. If reloading is not > supported at all, it's up to the loader to throw an appropriate > exception when the the previous spec is not None. If loading and > reloading doesn't make any difference, then they can just ignore it. > But when both are supported, but handled differently (as for extension > modules), then that can be detected, and the information from the old > spec (including the original loader and loader state) is available if > needed.
Our recent discovery about reloading should probably be reflected in the signature of finder.find_spec(): MetaPathFinder.find_spec(name, path=None, existing=None) PathEntryFinder.find_spec(name, existing=None) This way the finder has an opportunity to incorporate information from an existing spec into the spec it returns. reload() would make use of this by passing module.__spec__ (or None if the module has no __spec__) to _bootstrap._find_spec(). This approach should also address what you are looking for. I'd prefer it over passing the existing spec to exec_module(). The module (and its __spec__) should have everything exec_module() needs to do its job. We would still need to use loader.supports_reload() in reload(). However, it may make more sense to pass in the module-to-be-reloaded (after updating its __spec__ to the one found by _bootstrap._find_spec()). -eric _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
