Make parent formid a part of autogenerated oid

[ezag]

Re:

• Form.formid has no effect on Field.oid autogeneration deform#394
• Make parent formid a part of autogenerated oid deform#520

I'm not a native English speaker, so perhaps the docstring wording might be improved.

[stevepiercy]

This looks good to me, but I think it would be good to demonstrate both methods of having two forms on a page.

[stevepiercy]

Your English is better than my Russian. 😉 I have only a couple of corrections.

        # We do so by passing distinct ``formid`` keyword arguments to the
        # constructor of both forms.  As a result, the form's element identifiers
        # will inherit the parent's ``formid`` and will not conflict.
        # (Note: alternatively, we could create an ``itertools.count`` object
        # and pass that object as the ``counter`` keyword argument.)

Also after thinking about this, it would be good to demonstrate both examples of having two forms in a page. In other words, (1) let's keep the new method of explicitly providing the formid, and (2) would you please add the alternative example as you describe in your note?

That will require another test for the new widget, but I think it's worth doing.

[ezag]

I think that for an unfamiliar person it would be a bit misleading to have an example with the extra counter related code that could be removed with no apparent effect: setting distinct formids is a must anyway, and altered oids don't seem to matter from the example's standpoint.

That said, it is definitely worth having an example that demonstrates the counter feature; can you think of an appropriate one? And if not, do you think we can consider deprecating and/or removing the counter feature at all, in order to spare further code maintenance efforts?