Removing a cask triggers autoremove and removes lots of unrelated formulas about brew

[metayan]

Great. Thanks for the explanation. And the fix.

[MikeMcQuaid]

Step-by-step reproduction instructions (by running brew commands)

@metayan If you follow these instructions yourself: does it both install all these formulae and remove them? If you install them manually: are they removed every time?

[metayan]

Installed darktable 4.6.1 again, by tweaking the formula.
Then removed darktable.
This time the removal also tried to autoremove other things:

brew install --cask darktable

==> Downloading https://github.com/darktable-org/darktable/releases/download/release-4.6.1/darktable-4.6.1-x86_64.dmg
==> Installing Cask darktable
==> Moving App 'darktable.app' to '/Applications/darktable.app'
🍺  darktable was successfully installed!

brew remove darktable

==> Uninstalling Cask darktable
==> Backing App 'darktable.app' up to '/usr/local/Caskroom/darktable/4.6.1/darktable.app'
==> Removing App '/Applications/darktable.app'
==> Purging files for version 4.6.1 of Cask darktable
==> Autoremoving 1 unneeded formula:
ntfs-3g
Error: ntfs-3g is pinned. You must unpin it to uninstall.

brew info ntfs-3g

==> ntfs-3g: stable 2022.10.3, HEAD [pinned at 2017.3.23_3]
Read-write NTFS driver for FUSE
https://www.tuxera.com/community/open-source-ntfs-3g/
Installed
/usr/local/Cellar/ntfs-3g/2017.3.23_3 (89 files, 1.7MB) *
  Poured from bottle on 2020-06-20 at 01:53:27

Feel free to ask for more info if needed.

[metayan]

I just feel that removing a cask – that has no Homebrew dependencies – shouldn't remove any installed apps that have nothing to do with the cask in question.

[MikeMcQuaid]

What does brew autoremove --dry-run output?

[metayan]

brew autoremove --dry-run

==> Would autoremove 1 unneeded formula:
ntfs-3g

But it already removed all the autoremovable formulas before, when doing

brew remove darktable

as I reported above.
And ntfs-3g is pinned.

[MikeMcQuaid]

@metayan Can you paste the output of cat $(brew --prefix ntfs-3g)/INSTALL_RECEIPT.json? Thanks.

[metayan]

cat $(brew --prefix ntfs-3g)/INSTALL_RECEIPT.json |jq '.'

{
  "homebrew_version": "2.4.0-53-g748af98",
  "used_options": [],
  "unused_options": [],
  "built_as_bottle": true,
  "poured_from_bottle": true,
  "installed_as_dependency": null,
  "installed_on_request": null,
  "changed_files": [
    "sbin/mount_ntfs",
    "INSTALL_RECEIPT.json",
    "lib/pkgconfig/libntfs-3g.pc"
  ],
  "time": 1592610807,
  "source_modified_time": 1490262180,
  "HEAD": null,
  "stdlib": null,
  "compiler": "clang",
  "aliases": [],
  "runtime_dependencies": [
    {
      "full_name": "gettext",
      "version": "0.20.2"
    }
  ],
  "source": {
    "path": "/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/ntfs-3g.rb",
    "tap": "homebrew/core",
    "spec": "stable",
    "versions": {
      "stable": "2017.3.23",
      "devel": "",
      "head": "HEAD",
      "version_scheme": 0
    }
  }
}

[Rylan12]

  "installed_as_dependency": null,
  "installed_on_request": null,

These lines are causing autoremove to try and remove the formula. You can stop this from happening by running:

brew tab --installed-on-request ntfs-3g

I'm not totally sure why the values where written as null, but perhaps it has something to do with brew pin handling? Either way, we should handle this case by erring on the side of caution and not removing the formula. I've opened a PR to implement this.

[metayan]

The pinned formula was not removed, so no worries about that.

The issue is that 89 formulas were autoremoved when a cask was removed. Formulas that had nothing to do with the cask.
As can be seen above after

==> Autoremoving 89 unneeded formulae:

At least a request for confirmation that 89 formulas will be removed would be appropriate.

[Rylan12]

The PR merged should indeed fix this problem.

In this case, the problem seems to be that somehow the install metadata on your system was messed up, and did not properly mark that those formulae were installed at your request (as opposed to as a dependency for something else). I'm not sure at the moment why that happened, but the PR I merged strengthens the check so that Homebrew treats messed up metadata as "not sure, but let's assume they are installed on request and keep them around just in case." In the future, autoremove will only remove formulae that have "installed_on_request": false (as opposed to null) to avoid this from happening again.