Brew: The `system` method in formulae incompatible with Ruby `system`

[mislav]

Bug report

• [x] ran brew update and can still reproduce the problem? n/a
• [x] ran brew doctor, fixed all issues and can still reproduce the problem? n/a
• [x] ran brew config and brew doctor and included their output with your issue? n/a

What you were trying to do (and why)

In the install block of my formula, I was trying to pass environment variables like so:

def install
  system({ "FOO" => "bar" }, "env")
end

## What happened (include command output) A Ruby exception

Command output

Error: An exception occurred within a child process:
  TypeError: no implicit conversion of Hash into String
  

## What you expected to happen I've expected `system` to work the same way it does in Ruby: to accept a Hash as the 1st argument and apply the values as environment variables to the process https://ruby-doc.org/core-2.7.1/Kernel.html#method-i-system ## Step-by-step reproduction instructions (by running `brew` commands) 1. Add `system` call to `myformula.rb` 2. `brew install myformula` ## Output of `brew config` and `brew doctor` commands

HOMEBREW_VERSION: 2.4.16-144-g2314ddf
ORIGIN: https://github.com/Homebrew/brew
HEAD: 2314ddf9f5475b63d5e37d398d0a5990e0311afd
Last commit: 4 days ago
Core tap ORIGIN: https://github.com/Homebrew/homebrew-core
Core tap HEAD: 40d76cc32fa516569e82cb8907c9ec382fb38cf1
Core tap last commit: 16 minutes ago
Core tap branch: update-gh.rb-1599554327
HOMEBREW_PREFIX: /usr/local
HOMEBREW_CASK_OPTS: []
HOMEBREW_EDITOR: vim
HOMEBREW_MAKE_JOBS: 16
HOMEBREW_NO_AUTO_UPDATE: set
HOMEBREW_NO_INSTALL_CLEANUP: set
CPU: 16-core 64-bit kabylake
Homebrew Ruby: 2.6.3 => /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby
Clang: 11.0 build 1103
Git: 2.28.0 => /usr/local/bin/git
Curl: 7.64.1 => /usr/bin/curl
Java: 1.8.0_232-zulu-8.42.0.23
macOS: 10.15.6-x86_64
CLT: 1103.0.32.62
Xcode: 11.7

Please note that these warnings are just used to help the Homebrew maintainers
with debugging if you file an issue. If everything you use Homebrew for is
working fine: please don't worry or file an issue; just ignore this. Thanks!

Warning: Homebrew/homebrew-core is not on the master branch.

Check out the master branch by running:
  git -C "$(brew --repo homebrew/core)" checkout master

Warning: Some installed formulae are deprecated or disabled.
You should find replacements for the following formulae:
  [email protected]
  [email protected]

Warning: You have unlinked kegs in your Cellar.
Leaving kegs unlinked can lead to build-trouble and cause brews that depend on
those kegs to fail to run properly once built. Run `brew link` on these:
  docker

Warning: You have uncommitted modifications to Homebrew/brew.
If this is a surprise to you, then you should stash these modifications.
Stashing returns Homebrew to a pristine state but can be undone
should you later need to do so for some reason.
  cd /usr/local/Homebrew && git stash && git clean -d -f

Uncommitted files:
  ?? Library/Homebrew/vendor/bundle/ruby/2.6.0/gems/patchelf-1.1.1/lib/patchelf.rb
  ?? Library/Homebrew/vendor/bundle/ruby/2.6.0/gems/patchelf-1.1.1/lib/patchelf/cli.rb
  ?? Library/Homebrew/vendor/bundle/ruby/2.6.0/gems/patchelf-1.1.1/lib/patchelf/exceptions.rb
  ?? Library/Homebrew/vendor/bundle/ruby/2.6.0/gems/patchelf-1.1.1/lib/patchelf/helper.rb
  ?? Library/Homebrew/vendor/bundle/ruby/2.6.0/gems/patchelf-1.1.1/lib/patchelf/logger.rb
  ?? Library/Homebrew/vendor/bundle/ruby/2.6.0/gems/patchelf-1.1.1/lib/patchelf/mm.rb
  ?? Library/Homebrew/vendor/bundle/ruby/2.6.0/gems/patchelf-1.1.1/lib/patchelf/patcher.rb
  ?? Library/Homebrew/vendor/bundle/ruby/2.6.0/gems/patchelf-1.1.1/lib/patchelf/saver.rb
  ?? Library/Homebrew/vendor/bundle/ruby/2.6.0/gems/patchelf-1.1.1/lib/patchelf/version.rb

You have uncommitted modifications to Homebrew/homebrew-core.
If this is a surprise to you, then you should stash these modifications.
Stashing returns Homebrew to a pristine state but can be undone
should you later need to do so for some reason.
  cd /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core && git stash && git clean -d -f

Uncommitted files:
   M Formula/gh.rb
  ?? steps_output.txt

Warning: Homebrew's sbin was not found in your PATH but you have installed
formulae that put executables in /usr/local/sbin.
Consider setting the PATH for example like so:
  echo 'export PATH="/usr/local/sbin:$PATH"' >> ~/.zshrc

[MikeMcQuaid]

While we have a think about this in the mean time our DSL for this is:

with_env(FOO: "bar") do
  system "env"
end

or simply:

ENV["FOO"] = "bar"
system "env"

[mislav]

@MikeMcQuaid Thanks the the fast response and the workarounds! I did not know about with_env. I would prefer that since ENV["FOO"] = "..." can inadvertently affect subsequent processes.

Might all this warrant a mention in https://docs.brew.sh/Formula-Cookbook? I did not find instructions to set environment variables anywhere.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.