Inada Naoki wrote:
a) Document "optionxform must be idempotent".
b) Ensure all APIs calls optionxform exactly once, and document
> [that it must be idempotent in certain special situations]. I think the question that needs to be asked is whether optionxform is meant to be a canonicalising operation, or a transformation from an external to an internal form. Although the docs don't say so explicitly, it seems clear to me that the author of the module was thinking of it as a transformation to a canonical form. If that's what is intended, then idempotency is pretty much implied, from the definition of what canonical means. If something is already in canonical form, nothing needs to be done. The behaviour with regard to initialising from a dict that was raised in https://bugs.python.org/issue35838#msg334439 is probably an oversight, but there are at least two other ways that the module assumes idempotency: 1) The API does not provide any way of accessing an option *without* applying the transformation. This is a problem if e.g. you want to iterate over the keys and write values back. 2) The write() method writes out the transformed versions of option names. If this output is read back in, the transformation will necessarily be applied a second time. There doesn't seem to be any workaround for this. There may also be other ways in which idempotency is assumed that I haven't thought of. So, rather than try to have the docs list all the things that non-idempotency could break, it would be easier to simply document that idempotency is assumed. -- Greg _______________________________________________ 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
