Latin verse scanners recurse infinitely

From prosody.latin.hexameter_scanner.py:

        # if the line doesn't scan "as is", if may scan if the optional i to j transformations
        # are made, so here we set them and try again.
        if self.optional_transform and not verse.valid:
            return self.scan(original_line, optional_transform=True, dactyl_smoothing=True)

If this second scan fails as well (e.g. if a line is too badly malformed for optional_transform to fix it), it recurses infinitely until it crashes with a RecursionError. The same holds true for HendecasyllableScanner and PentameterScanner.

The condition should instead be:

        if self.optional_transform and not optional_transform and not verse.valid:

This will return an invalid verse if the optional transformations didn’t help, rather than spiralling forever. (I’d submit this as a pull request, but I don’t have permission.)

[todd-cook]

Your use case brings up a good point, there are number of lines in hexameter poems that are incomplete, often deliberately so, and so method of meter detection or meter for what is there would be helpful too.

@dstelzer Thanks for the example. I’ll take a look at this. I’ll take another crack at the code; there’s a few things to fix.

[kylepjohnson]

Also @dstelzer please provide text of poetry, for at least one meter type, that causes this recursion to happen.