Fail on a multiline distribution package summary

[webknjaz]

Summary of changes

This is the second iteration on:

• Newlines in the description field produce a malformed PKG-INFO #1390
• Description cannot contain a newline. #2470

Pull Request Checklist

• Changes have tests
• News fragment added in changelog.d/.
  (See documentation for details)

[webknjaz]

The problem with this wording is that it doesn't help figure out what's wrong. When I saw a warning in the middle of the console output, the only way to understand what it was, was to read the source code. This is not the best UX, is it?

[jaraco]

Indeed, it's not the best user experience. But I expect these errors to be rare. Also, now that they're raised as an exception (or if you'd passed -We), you'll see the traceback, which does point to single_line(self.get_description()), which does indicate where the error is.

[boegel]

I've just learned that we (accidentally) had a newline in the description of one or our packages, so we're hitting the "ValueError: Newlines are not allowed" error.

This is easy to fix for new versions of our package (see easybuilders/easybuild-easyblocks#2623), but it does leave older versions of our package impossible to install with setuptools>=59.0.0.

Have you considered simply stripping out newlines from the package description instead, rather than making it a hard error?

At least that way, existing package releases where one or more newlines are (accidentally) included in the description are not utterly broken (with no easy way around it, other than a forced install of setuptools<59.0.0)...

[webknjaz]

@boegel you could just publish wheels for those versions

[boegel]

@webknjaz I feel that would be a rather excessive effort to fix a problem that boils down to an extra newline character in the package description which can easily be filtered out by setuptools, rather than making that a hard error...

[webknjaz]

It was a warning for a year already so people had time to fix their packages.

[boegel]

It was a warning for a year already so people had time to fix their packages.

Sure, but it is very easy to overlook the warning since it drowns in the produced output easily.

Again, hard breaking the installation of packages that have been released already just because there's an extra newline seems a bit much to me.

It would be quite easy to just filter out the newline character, no? If that would be an accepted change, I'm happy to open a pull request for it.

[webknjaz]

They are already broken, though. Also, I wouldn't make assumptions about one newline or many, or other things that may have caused people to add multiple lines (I've seen cases with a lot more than one FWIW).
Let's not enable invalid metadata.

[boegel]

They are already broken, though. Also, I wouldn't make assumptions about one newline or many, or other things that may have caused people to add multiple lines (I've seen cases with a lot more than one FWIW). Let's not enable invalid metadata.

In what sense are packages that have newlines in the description broken with setuptools < 59.0.0?
We haven't seen any problems whatsoever with a newline included in the description up until now...

Automagically replacing a newline with a space in the package description because the newline causes trouble somehow isn't "enabling invalid metadata" imho. In fact, it's making sure that the metadata is not invalid (for the installed package).