formula_installer: improve no-bottle error message

[carlocab]

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Closes #10180.

This PR changes the error message when you try to install python@3.9 and you have no CLT installed to:

❯ HOMEBREW_NO_AUTO_UPDATE=1 brew install python@3.9
Error: python@3.9: unable to pour bottle!
The bottle needs the Apple Command Line Tools to be installed.
  You can install them, if desired, with:
    xcode-select --install
You can try to install from source with e.g.
  brew install --build-from-source python@3.9
Please note building from source is unsupported. You will encounter build
failures with some formulae. If you experience any issues please create pull
requests instead of asking for help on Homebrew's GitHub, Twitter or any other
official channels.

If the formula does not specify a pour_bottle? method but also has no bottles:

❯ HOMEBREW_NO_AUTO_UPDATE=1 brew install a2ps
Error: a2ps: unable to pour bottle!
You can try to install from source with e.g.
  brew install --build-from-source a2ps
Please note building from source is unsupported. You will encounter build
failures with some formulae. If you experience any issues please create pull
requests instead of asking for help on Homebrew's GitHub, Twitter or any other
official channels.

I suspect there may be more refactoring in order for the pour_bottle? method in formula_installer.rb, but I'd prefer to address those later.

[BrewTestBot]

Review period will end on 2020-12-31 at 14:52:26 UTC.

[Rylan12]

I think the no bottle available! message is a tad misleading in this case. Maybe instead: bottle conditions not met!. No bottle available feels more "final" as if it's saying "sorry there's nothing you can do except build from source" while this is more like "before you can use a bottle you must do this".

Maybe that's not the case for all formulae that use pour_bottle?, though.

[carlocab]

How about no suitable bottle available?

[Rylan12]

Sorry, wasn't clear with what I was thinking.

I was thinking this "unable to pour bottle" message would be only for instances where formula.pour_bottle? is false.

When this message is showing in situations like no ARM bottles are available, I think it makes sense to still have the "no bottle available" message. That's a little more accurate to what the exact issue is for the user, I think.

[carlocab]

I agree, but I'm still mulling over the best way to implement it.

For instance, maybe it's enough to just add && formula.pour_bottle? to the conditions required by the if statement and drop any of the changes I've made here so far.

Alternatively, I could add an else after the second message += to state explicitly that there isn't a bottle...

[Rylan12]

Ah, you know what? I think this is what you want to do instead:

Change the !pour_bottle? condition on line 244 (just above you changes) to !pour_bottle?(output_warning: true)

You may also need to adjust the messaging. See if that gives a better result. pour_bottle? is already calling formula.pour_bottle? and it displays the message there.

[carlocab]

I've considered that too, but decided against it since adjusting the messaging already in the pour_bottle? method seemed overly complicated... but I'll think about it again.

[carlocab]

Thinking about it some more, I don't think I should change the messaging in the pour_bottle? method, since that has implications on Linux as well. Whatever changes need to be made will have to be where I've already proposed them in this PR. Still thinking about the right way to do it though.

[BrewTestBot]

Review period skipped due to critical label.