Homebrew won't brew any more

Question

On my MacMini with El Capitan I can't run brew any more. I get the following Error:

/usr/local/Library/Homebrew/config.rb:34:in `initialize': no implicit conversion of nil into String (TypeError)
    from /usr/local/Library/Homebrew/config.rb:34:in `new'
    from /usr/local/Library/Homebrew/config.rb:34:in `<top (required)>'
    from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from /usr/local/Library/Homebrew/global.rb:18:in `<top (required)>'
    from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from /usr/local/Library/brew.rb:10:in `<main>'

The permissions of /usr/local are correct.

The config.rb file, which I haven't changed looks like this:

def cache
  if ENV["HOMEBREW_CACHE"]
    Pathname.new(ENV["HOMEBREW_CACHE"]).expand_path
  else
    # we do this for historic reasons, however the cache *should* be the same
    # directory whichever user is used and whatever instance of brew is executed
    home_cache = Pathname.new("~/Library/Caches/Homebrew").expand_path
    if home_cache.directory? && home_cache.writable_real?
      home_cache
    else
      Pathname.new("/Library/Caches/Homebrew").extend Module.new {
        def mkpath
          unless exist?
            super
            chmod 0775
          end
        end
      }
    end
  end
end

HOMEBREW_CACHE = cache
undef cache

# Where brews installed via URL are cached
HOMEBREW_CACHE_FORMULA = HOMEBREW_CACHE+"Formula"

unless defined? HOMEBREW_BREW_FILE
  HOMEBREW_BREW_FILE = ENV["HOMEBREW_BREW_FILE"] || which("brew").to_s
end

# Where we link under
HOMEBREW_PREFIX = Pathname.new(ENV["HOMEBREW_PREFIX"])

# Where .git is found
HOMEBREW_REPOSITORY = Pathname.new(ENV["HOMEBREW_REPOSITORY"])

HOMEBREW_LIBRARY = Pathname.new(ENV["HOMEBREW_LIBRARY"])
HOMEBREW_CONTRIB = HOMEBREW_REPOSITORY/"Library/Contributions"

# Where we store built products
HOMEBREW_CELLAR = Pathname.new(ENV["HOMEBREW_CELLAR"])

HOMEBREW_LOGS = Pathname.new(ENV["HOMEBREW_LOGS"] || "~/Library/Logs/Homebrew/").expand_path

HOMEBREW_TEMP = Pathname.new(ENV.fetch("HOMEBREW_TEMP", "/tmp"))

unless defined? HOMEBREW_LIBRARY_PATH
  HOMEBREW_LIBRARY_PATH = Pathname.new(__FILE__).realpath.parent.join("Homebrew")
end

HOMEBREW_LOAD_PATH = HOMEBREW_LIBRARY_PATH

The same error occurs with brew, brew doctor, brew update etc.

Any ideas, what could be wrong?

Answer 1

I had the same issue - seemed to be the result of a brew update that could not complete due to permissions issues.

First I reset the repo to the latest head:

cd /usr/local/bin
git reset --hard HEAD

Then I could run:

brew doctor

Which found permissions issues. Fixing those permissions as per instructions finally allowed me to run:

brew update