I was upgrading the go version of my personal project the other day.

I moved from go 1.16 to go 1.19. I had to come out with a new version. I upgraded my custom brew package as I always do; fix the url and sha fields in the Formula, fix the basic test under test area.

I pushed my changes and started to wait github actions’ checks. Checks are failed, due to brew’s formula style guide:

==> brew style vigo/statoo
==> FAILED
Full style vigo/statoo output
  Formula/statoo.rb:18:5: C: Use generate_completions_from_executable DSL instead of (bash_completion/"statoo").write #{bin}/statoo bash-completion.
      (bash_completion/"statoo").write `#{bin}/statoo bash-completion`
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  2 files inspected, 1 offense detected
  Error: Use `generate_completions_from_executable` DSL instead of `(bash_completion/"statoo").write `#{bin}/statoo bash-completion``.

In the install part of the formula; bash completion related setup was written as shown below:

def install
  system "go", "build", *std_go_args
  (bash_completion/"statoo").write `#{bin}/statoo bash-completion`
end

Checker was telling me that, I should use generate_completions_from_executable DSL instead of old one. Well, what was that? when was changed? Let’s fix this :) First, let’s read the docs, then change the code to:

def install
  system "go", "build", *std_go_args
  generate_completions_from_executable(bin/"statoo", "bash-completion", "completions", shells: [:bash])
end

Break down of args:

• bin/"statoo" is the executable path
• bash-completion is an arg for statoo executable, generates bash related completion code.
• completions is the base_name
• Completion code is compatible with bash only, therefor I set the shel :bash only.

I spent an hour to fix and understand the problem and solution. I couldn’t find any examples or documentation about this new formula style change… This is why I’m writing this blog post so that will be useful to other brewers :)

Here is the function signature of generate_completions_from_executable:

generate_completions_from_executable(
  *commands, 
  base_name: name, 
  shells: [:bash, :zsh, :fish], 
  shell_parameter_format: nil
) ⇒ void

I hope this post will help, happy brew packaging! You can check project and custom brew package here:

• https://github.com/vigo/statoo (project)
• https://github.com/vigo/homebrew-statoo (brew package)