Enable HOMEBREW_AUTOREMOVE by default

[MikeMcQuaid]

Enabled HOMEBREW_AUTOREMOVE by default, and added HOMEBREW_NO_AUTOREMOVE to disable it.

I've been running this for years and it's been rock-solid. An incoming minor release feels like a good time to change this default and document it.

[apainintheneck]

I forgot about this one though I've had it set for years now too. I'm happy that it's finally the default.

[jacktose]

Whoa! That removed all my build dependencies! I don't want to have to re-build all of those every time I upgrade a built formula. Is there an option for the autoremove logic to leave formulae that were installed as build dependencies?

E.g.:

$ brew autoremove -n
==> Would autoremove 1 unneeded formula:
sqlite
$ brew uses --installed sqlite
$ brew uses --installed sqlite --include-build
util-linux
$ brew info util-linux
==> util-linux: stable 2.40.1
...
Installed
/data/shared/lusers/enneking/homebrew/Cellar/util-linux/2.39.3 (412 files, 24.4MB)
  Built from source on 2023-12-18 at 16:36:02

[Bo98]

Hmm yeah that's probably a fair point for the non-default-prefix and/or unsupported OS case. Maybe worth disabling by default on those environments.

[carlocab]

Yea, we already skip attempting to reinstall outdated dependents (as long as linkage isn't broken) if it will result in a source build.

[carlocab]

Whoa! That removed all my build dependencies! I don't want to have to re-build all of those every time I upgrade a built formula. Is there an option for the autoremove logic to leave formulae that were installed as build dependencies?

Not yet, but you can export HOMEBREW_NO_AUTOREMOVE=1 for now.

[ZhongRuoyu]

Is there an option for the autoremove logic to leave formulae that were installed as build dependencies?

I have an in-progress work that allows you to explicitly mark/unmark formulae as installed on request, as discussed in #17125 (comment). When a formula is installed on request, it does not get removed by brew autoremove.

My Mac is with Genius Bar right now. I'll make a PR when I get it back.

[apainintheneck]

Whoa! That removed all my build dependencies! I don't want to have to re-build all of those every time I upgrade a built formula. Is there an option for the autoremove logic to leave formulae that were installed as build dependencies?

Maybe we could just exclude all build dependencies used by formula that were built-from-source?

[MikeMcQuaid]

Maybe we could just exclude all build dependencies used by formula that were built-from-source?

This seems like the right thing to do 👍🏻

[jacktose]

Maybe we could just exclude all build dependencies used by formula that were built-from-source?

That's exactly what I'd hope would happen.

[apainintheneck]

Ah, I'm an idiot. I should have checked the existing logic before commenting. It looks like it already accounts for build dependencies when checking what's autoremovable. Maybe there's a bug in the current logic.

brew/Library/Homebrew/utils/autoremove.rb

Lines 32 to 52 in c6368be

	# An array of all installed {Formula} without runtime {Formula}
	# dependents for bottles and without build {Formula} dependents
	# for those built from source.
	# @private
	sig { params(formulae: T::Array[Formula]).returns(T::Array[Formula]) }
	def formulae_with_no_formula_dependents(formulae)
	dependents = T.let([], T::Array[Formula])
	formulae.each do |formula|
	dependents += formula.runtime_formula_dependencies
	# Ignore build dependencies when the formula is a bottle
	next if formula.any_installed_keg&.tab&.poured_from_bottle
	formula.deps.select(&:build?).each do |dep|
	dependents << dep.to_formula
	rescue FormulaUnavailableError
	# do nothing
	end
	end
	formulae - dependents
	end

[jacktose]

I wish I'd saved the output when it unexpectedly removed like 15 deps. But my sqlite example above shows there's still something amiss.

[apainintheneck]

Yeah, I agree. It might be worth making a new issue about it while we investigate.

[MikeMcQuaid]

Yes, please open issue(s) here rather than talking on a merged PR, thanks.

[jacktose]

Opened #17433.