bdist_wheel should support custom platform tags

[agronholm]

Originally reported by: Timothy Allen (Bitbucket: OptiverTimAll, GitHub: OptiverTimAll)

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Now that Pip automatically caches built wheels, and since the cache may be in a shared location, it would be useful to allow people to invent custom platform-tags so that wheels compiled for different scenarios can be kept apart.

This has been discussed in pip's issue tracker and in a distutils-sig thread, with positive reception in both. Some of the concrete use-cases listed include:

• Users may want pip/wheel to distinguish wheels built on platforms where pip cannot reliably determine a platform tag on its own, like linux_x86_64
• Users may want pip/wheel to distinguish wheels built with security-hardening flags, so non-hardened wheels are not deployed into production
• Users may want pip/wheel to distinguish wheels built with compiler-flags that enable the use of CPU instructions that are not yet widely available.

bdist_wheel currently supports a --plat-name option, but it has some unfortunate behavour: so far as I can tell, if you give it a custom platform name and build a pure-Python package, the option is silently ignored. On the other hand, if you build a package that includes a C module, the process dies with an assertion error.

Perhaps --plat-name and its behaviour could be deprecated, and a new --platform-tag option (named for consistency with --python-tag and the terminology of PEP0425) that accepts any tag that meets the character set requirements (alphanumerics and underscores, if I read the PEP correctly).

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• Bitbucket: https://bitbucket.org/pypa/wheel/issue/144

[agronholm]

Original comment by Andrés Díaz (Bitbucket: ajdiaz, GitHub: ajdiaz):

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I created the PR #60 to allow --plat-tag and also "force" platform tag even when pure python packages.

Feedback is welcome!

[agronholm]

Original comment by Daniel Holth (Bitbucket: dholth, GitHub: dholth):

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I like the override feature.

I notice you changed the command line argument name to tag, but changed
a lot of tag variables to name in the source.

It is probably not OK to remove the old command line argument.

[agronholm]

Original comment by Andrés Díaz (Bitbucket: ajdiaz, GitHub: ajdiaz):

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Yep, I agree. I changed the argument name because the Timothy's comment in the issue recommended to change the argument name to be more close to the PEP notation and also because plat_name attribute is also used by distutil.cmd so to keep the variable will require more work. But in general, I agree that we should keep the original argumet name.

I could try to fix that and update the PR if there are more comments about that.

Thanks for the feedback!!

[agronholm]

Original comment by Nate Coraor (Bitbucket: natefoo, GitHub: natefoo):

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Thanks @ajdiaz, I merged your pull request #60 and have some additional changes and tests in e3c7215947c0

[agronholm]

Original comment by Nate Coraor (Bitbucket: natefoo, GitHub: natefoo):

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I found a bug in my changes that broke pure python wheels (they were no longer getting the any tag). I've fixed this in development and wrote a test to catch it in the future, but as a result, I've changed my mind on the use of --plat-tag deprecating --plat-name. --plat-name is a standard option through most of the commands and wheel uses set_undefined_options() to have bdist set it. I think we need to follow suit here.

[agronholm]

Original comment by Nate Coraor (Bitbucket: natefoo, GitHub: natefoo):

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Changed as per my comment in e3747d1e06d2.