jdx/mise · error · RuntimeError

completion generation failed: #{cmd.join(" ")}

Error message

completion generation failed: #{cmd.join(" ")}

What it means

The shim's completion generator builds a command to ask the tool itself to emit shell completions (including click-style env-var completion), runs it via Open3.capture2, and raises if the process exits non-zero. The generated output is then written into the completion directory.

Source

Thrown at src/system/packages/brew/shim.rb:853

    shells.each do |shell|
      completion_dir = { bash: bash_completion, zsh: zsh_completion, fish: fish_completion }.fetch(shell)
      file_name = { bash: base_name, zsh: "_#{base_name}", fish: "#{base_name}.fish" }.fetch(shell)
      shell_arg = case shell_parameter_format
                  when nil then shell.to_s
                  when :flag then "--#{shell}"
                  when :arg then "--shell=#{shell}"
                  when :none then nil
                  when :click then nil # click uses env vars; handled below
                  when String then "#{shell_parameter_format}#{shell}"
                  end
      cmd = commands.map(&:to_s)
      cmd << shell_arg unless shell_arg.nil?
      env = {}
      if shell_parameter_format == :click
        env["_#{base_name.upcase.tr("-", "_")}_COMPLETE"] = "#{shell}_source"
      end
      output, status = Open3.capture2(env, *cmd)
      raise "completion generation failed: #{cmd.join(" ")}" unless status.success?
      completion_dir.mkpath
      (completion_dir + file_name).write(output)
    end
  end

  def time = Time.now

  def post_install; end

  # unknown instance helpers: fail loudly
  def method_missing(name, *args, &block)
    shim_unsupported!("#{name} (install-time helper)")
  end

  def respond_to_missing?(_name, _include_private = false) = true

  class InreplaceText
    attr_reader :text

View on GitHub (pinned to afd2eddd3a)

Solutions

1. Run the completion command manually to see the tool's error output
2. Check the shell name is one the tool supports (bash/zsh/fish) and matches the installed tool version
3. For click tools, verify base_name matches the click program so the env var name is right
4. Update the formula to a tool version that supports the requested shell/format

Example fix

# before
shell_completion :nushell, "mytool"
# after
shell_completion :bash, "mytool" # or :zsh/:fish, per tool support

# preflight: confirm the tool supports the shell
supported = %w[bash zsh fish]
raise "unsupported shell #{shell}" unless supported.include?(shell.to_s)

begin
  generate_completions(shell)
rescue RuntimeError => e
  raise unless e.message.start_with?("completion generation failed")
  warn "completion generation failed for #{shell}: #{e.message}"
end

When it happens

Trigger: The tool's completion subcommand fails: wrong shell name passed, unsupported shell_parameter_format, tool version lacking the completion command, or the completion binary errors at runtime.

Common situations: Formula declaring shell_completion with a shell name the tool doesn't support (e.g. :nushell on older versions); click-based tools where the base_name-derived env var doesn't match the actual click program name; PATH issues during install.

Related errors

• brew-cask: failed to generate {} completions from {}: {}
• brew-cask: failed to generate {} completions from {}: {}
• command failed: #{args.join(" ")}
• patch failed:\n#{output}
• command failed: #{pretty}

AI-assisted analysis of jdx/mise@afd2eddd3a (2026-09-09). Data as JSON: /api/errors/b5f5032276e6152f. Report an issue: GitHub.