On 18 Jun 2017, at 19:21, Barry Scott <barry@barrys-emacs.org> wrote:

On 14 Jun 2017, at 07:33, Nick Coghlan <ncoghlan@gmail.com> wrote:

On 14 June 2017 at 13:02, Mahmoud Hashemi <mahmoud@hatnote.com> wrote:
That would be amazing! If there's anything I can do to help make that
happen, please let me know. It'll almost certainly save that much time for
me alone down the line, anyway :)

The `IMPORT_FROM` opcode's error handling would probably be the best
place to start poking around:
https://github.com/python/cpython/blob/master/Python/ceval.c#L5055

If you can prove the concept there, that would:

1. Directly handle the "from x import y" and "import x.y as name" cases
2. Provide a starting point for factoring out a "report missing module
attribute" helper that could be shared with ModuleType

As an example of querying _frozen_importlib state from C code, I'd
point to https://github.com/python/cpython/blob/master/Python/import.c#L478

I had thought that the solution would be in the .py implementation of the import
machinery not in the core C code.

I was going to simply keep track of the names of the modules that are being imported
and raise an exception if an import attempted to import a module that had not completed
being imported. It seems from a quick loom at the code that this would be practical.

Are you saying that there is a subtle point about import and detection of cycles that
means the work must be done in C?

It seemed that PyImport_ImportModuleLevelObject() always calls out the

interp->importlib. For example:

value = _PyObject_CallMethodIdObjArgs(interp->importlib,

&PyId__lock_unlock_module, abs_name,

NULL);

Where interp->importlib is the frozen importlib.py code I thought.

I'd assumed that I would need to change the importlib.py code and

build that as the frozen version to implement this.

Barry

Barry

Cheers,
Nick.

P.S. I also double checked that ImportError & AttributeError have
compatible binary layouts, so dual inheritance from them works :)

--
Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia
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