Bug report

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• ran brew update and can still reproduce the problem?
• ran brew doctor, fixed all issues and can still reproduce the problem?
• ran brew config and brew doctor and included their output with your issue?

What you were trying to do (and why)

I have a script that uses brew ruby -e to print the path to a homebrew formula. I can evaluate the expression successfully with brew irb, but it fails with brew ruby. For example, to print the path to the qt formula on linuxbrew:

$ brew irb
...
irb(main):001:0> puts "qt".f.path
/home/linuxbrew/.linuxbrew/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/qt.rb
...

What happened (include command output)

Though this expression can be evaluated with brew irb, it fails with brew ruby complaining that f is an uninitialized constant String::Formulary.

$ brew ruby -e 'puts "qt".f.path'

Traceback (most recent call last):

1: from -e:1:in <main>' /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/dev-cmd/irb.rb:14:in f': uninitialized constant String::Formulary (NameError)
  

What you expected to happen

I expect brew ruby to work the same as brew irb.

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

1. Run brew ruby -e 'puts "qt".f.path'

I used git bisect to trace the last "good" commit to 6750448 and the regression to 1b9002c. I've added a test in scpeters@b532e79 on top of the "good" commit that can be included in a pull request that fixes this.

Output of brew config and brew doctor commands

$ brew config
HOMEBREW_VERSION: 2.5.12-369-gc003070
ORIGIN: https://github.com/Homebrew/brew
HEAD: c00307024ffe7b6de9f87305830f0c867e1e8a19
Last commit: 2 hours ago
Core tap ORIGIN: https://github.com/Homebrew/linuxbrew-core
Core tap HEAD: 4fb3f5d8c44f897eaa6da6be59a420cec13f13f3
Core tap last commit: 4 hours ago
Core tap branch: master
HOMEBREW_PREFIX: /home/linuxbrew/.linuxbrew
HOMEBREW_CASK_OPTS: []
HOMEBREW_DISPLAY: :1
HOMEBREW_MAKE_JOBS: 8
Homebrew Ruby: 2.6.3 => /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/2.6.3_2/bin/ruby
CPU: octa-core 64-bit ivybridge
Clang: 6.0 build 600
Git: 2.17.1 => /usr/bin/git
Curl: 7.58.0 => /usr/bin/curl
Kernel: Linux 5.4.0-53-generic x86_64 GNU/Linux
OS: Ubuntu 18.04.5 LTS (bionic)
Host glibc: 2.27
/usr/bin/gcc: 8.4.0
/usr/bin/ruby: 2.5.1
glibc: N/A
gcc: N/A
xorg: N/A

$ brew doctor
Your system is ready to brew.