Provides a config option to ignore warnings about Xcode being outdated

[ctaintor]

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I'm adding this since in our organization, there are parts of the organization which are slower about updating xcode versions. In our case we are using an older version of Xcode 15 – so, still on an Xcode from this year, just not 15.4. This is because we rely on Simulator visual screenshots and these can sometimes change very slightly between Xcode versions. We want to silence the warning for the users who are updating Xcode in a controlled manner.

[carlocab]

A bit on the fence about this, but I won't block it if other maintainers are fine with it.

[carlocab]

I'm inclined not to document this at all:

Suggested change

	HOMEBREW_NO_WARN_OUTDATED_XCODE: {
	description: "If set, Homebrew will not warn about using outdated (but still compatible) Xcode versions.",
	boolean: true,
	},

in which case you should ignore my other suggestion about Homebrew::EnvConfig (since that relies on the env variable being in env_config.rb).

[p-linnane]

I'm 👎 on this. Silencing a legitimate warning because an enterprise is slow to update doesn't make sense to me.

[ctaintor]

Right above this suggested change, there is code to ignore these warnings in github actions. The reason that is wanted in the github actions environment is similar to the reason for this PR – there are environments where you cannot update Xcode the day it comes out and you'd prefer not to have a warning print.

It feels like removing the linked code and instead setting HOMEBREW_NO_WARN_OUTDATED_XCODE=1 for the CI environment is another way to reason about this change. In that way, it would have clear value to the Homebrew project while also enabling users of Homebrew to ignore the warning when their project work means that they can't upgrade Xcode immediately.

[SMillerDev]

I don't think we should silence these, they are legitimate warnings and companies being slow to update doesn't stop that. Just like we don't hide the warnings that macOS versions are outdated.

[ctaintor]

Just for clarity – I am talking about using a version of Xcode 15 which is not the latest (the latest version of Xcode is 15.4 and was released in May) but was still released less than 1 year ago. I am just asking that the same control of warning messages used for the CI is exposed to normal users. Also – any debugging or support requested from the brew community always includes the ´brew doctor´output, so this warning would be printed there.

I went and looked at how older macOS versions are handled by brew. I think there are some differences from this:

• the oldest version of macOS supported by brew is based on the major release, not a minor release
• the oldest release of macOS supported by brew is 4 years old
• a brew user can configure the oldest version supported by setting HOMEBREW_MACOS_OLDEST_SUPPORTED. It can be moved back to support even older versions of macOS.

[Bo98]

Worth noting that this warning already should not appear if you are installing from bottles and only when installing from source. I'm assuming you're using a third-party tap that doesn't use bottles?

Does your xcode-select -p pointing to the CLT? We could maybe silence this warning on the condition that the CLT is used (and the formula in question doesn't use depends_on :xcode).

[ctaintor]

Thanks for pointing that out – I was unaware. Yes, we are using our own (internal) tap – most are built from source, mostly because the infra to build/update bottles is a challenge to set up. (None depend_on xcode). They are node, python or go CLIs.

Does your ´xcode-select -p´ pointing to the CLT?

I'm not entirely sure what you mean – it points to the /Applications/Xcode-15.2.0.app/Contents/Developer