combine fails when nothing is produced by many about parsy HOT 2 CLOSED

Thanks for your response. As for a minimal reproducible example, I don’t believe I could get any more minimal than what was shown, and the error was certainly reproducible with the given code and input. If that wasn’t enough, then as a maintainer you could have closed the ticket without looking but as a user, I couldn’t have helped it any other way.

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It looks like you have a bug in your parser, in particularly, the line for node - the lambda takes a single argument, but many() produces multiple values, and combine passes them using *args - see https://parsy.readthedocs.io/en/latest/ref/methods_and_combinators.html#parsy.Parser.combine . This means that the node definition will work if the previous parser produces an iterable that has exactly one value but fail for multiple or zero value.

Here is a simplified example:

In [1]: from parsy import *
In [2]: node = string(';') >> string('X').many().combine(lambda x: {'properties': x})
In [3]: node.parse(';X')
Out[3]: {'properties': 'X'}
In [4]: node.parse(';XX')
TypeError: <lambda>() takes 1 positional argument but 2 were given

In [5]: node.parse(';')
TypeError: <lambda>() missing 1 required positional argument: 'x'

You need to use a lambda that takes multiple arguments as *args, or more probably just use map - https://parsy.readthedocs.io/en/latest/ref/methods_and_combinators.html#parsy.Parser.map

BTW, normally I would have just closed this issue without looking at the code, because it's not a great report. A good bug report should be a Minimal Reproducible Example - see also Craft Minimal Bug Reports - (I should add these to the README for submitting reports). If you don't do this, you are in effect asking the maintainers of the project to debug your code for you (as I have done) and often if you do it yourself, you will discover where the bug is.

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