Warn when doing a PEP 517 build in presence of --global-option

[sbidoul]

• Warn when doing a PEP 517 build in presence of --global-option
• Warn instead of erroring out when doing a PEP 517 build in presence of --build-option

--build-option and --global-option are not supported by PEP 517.
Before, --global-option was silently ignored and --build-option caused an error.

We now warn if any of the two is present, in order to be more explicit about ignored options, and to avoid any backward compatibility issues when we start passing --build-option in the install command.

This is a first step towards #9769. I'll see if I can split #9422 in small PRs to facilitate review.

[pradyunsg]

Can we keep the error for --build-option? I'm not sure we gain anything by relaxing behavior there.

[sbidoul]

@pradyunsg we gain symmetry in the behaviour of --global-option and --build-option. I like symmetry :)
I don't think anyone would actually rely on this erroring out ?
Also, when the install command will accept --build-option it might be more flexible to not fail abruptly in this case (say, when someone installs a mix of legacy and PEP 517 with --build-option enabled).

[pradyunsg]

I don't think anyone would actually rely on this erroring out?

No, but I guess they will rely on it not erroring out in the future; especially since the warning isn't stating that we'd disable it in the future or something to discourage it. If we're relaxing some behaviour, we should probably have a good reason for it; because getting stricter is much harder later.

Anyway, I don't feel strongly about this and I don't have enough context to understand how this change helps the broader bigger PR. Just to be overly verbose, I'm not blocking this or whatever; just trying to understand what is happening. :)

[sbidoul]

@pradyunsg thanks for the feedback.

I'm not too worried about getting stricter in the future, because we ignore the option so it's a no-op.

TBH the scenarios in which the error would actually be an issue might be a bit far fetched (e.g. when someone installs a mix of legacy and PEP 517 with --build-option enabled). But I prefer being flexible with users here. And as a nice bonus, the code is cleaner with the same processing for --global-option and --build-option in this area, and build_wheel_pep517() that needs not be concerned anymore with an option that has nothing to do with it.

[pradyunsg]

TBH the scenarios in which the error would actually be an issue might be a bit far fetched (e.g. when someone installs a mix of legacy and PEP 517 with --build-option enabled).

Well, maybe. We're switching from error to fairly-silent-ignore... I guess it triggers some tripwire in my brain. For the future me reading this, these options can be set on a per-requirement basis too.

I guess my question is what's the long term plan here? Do we plan to allow these in some form for PEP 517 builds? If not, I guess prefer we change the calls to be calls to deprecated for 21.3 instead of logger.warn.

[pradyunsg]

(oh yea, and the code is definitely cleaner like this)

[sbidoul]

Do we plan to allow these in some form for PEP 517 builds?

I don't think so. For PEP 517 it will be some sort of config-settings (#5771), so a new option (unless config-settings end up never being needed by anyone, we'll see with the feedback we get on #9769).

If not, I guess prefer we change the calls to be calls to deprecated for 21.3 instead of logger.warn.

I suppose we'll deprecate --build-options and --global-option, at the same time as we deprecate all calls to setup.py bdist_wheel. But that is premature: we first need to deprecate setup.py install and we do that by using setup.py bdist_wheel which is softer transition than enforcing PEP 517.

[uranusjr]

It kind-of-sort-of makes sense to re-use --build-option for PEP 517 config_settings, but it’s probably easier in more than one way if we invent a new option for it. The deprecation of --build-option and --global-option will also help us identify if we really need config_settings at all, i.e. what people are using --build-option and --global-option right now for, minus the location options (e.g. --prefix).

[sbidoul]

A deprecation without a replacement is not ideal, though. What we could do is add an info or warning level message when build_wheel_legacy is called with build_options or global_options. This message could direct users to a GitHub issue asking them to describe their use cases.