bpo-19610: setup() now raises TypeError for invalid types

[berkerpeksag]

The Distribution class now explicitly raises an
exception when 'classifiers', 'keywords' and
'platforms' fields are not specified as a list.

https://bugs.python.org/issue19610

[cryvate]

LGTM code + docs.

Is there a test that qualifiers cannot be a string? Might be a good way to make sure this isn't accidentally added, contradicting the docs.

[berkerpeksag]

Quoting @cryvate:

Is there a test that qualifiers cannot be a string? Might be a good way to make sure this isn't accidentally added, contradicting the docs.

Do you mean is there a test for fields other than keywords, platforms and classifiers? Distribution.finalize_options() only converts a string to a list for keywords and platforms fields:

cpython/Lib/distutils/dist.py

Lines 602 to 608 in b98f171

	for attr in ('keywords', 'platforms'):
	value = getattr(self.metadata, attr)
	if value is None:
	continue
	if isinstance(value, str):
	value = [elm.strip() for elm in value.split(',')]
	setattr(self.metadata, attr, value)

[cryvate]

I meant there could be a test that this 'string to list' conversion does *not* happen for classifiers (I.e. the current behaviour).

[berkerpeksag]

There is no "string to list" test but "tuple to list" test for classifiers: test_classifier_invalid_type

I think that covers the following branch:

if not isinstance(value, list):
    ...

And since the implicit "string to list" conversation only happens for 'keywords' and 'platforms' fields, I think we're good to go.

Please feel free to send another PR or an example if I misunderstand your comment, thanks!