function _gb_commands() {
    local ret=1 state
    _arguments -C ':command:->command' '*::options:->options' && ret=0

    case $state in
      (command)

        local -a subcommands
        subcommands=(
          "build:build a package"
          "doc:show documentation for a package or symbol"
          "env:print project environment variables"
          "generate:generate Go files by processing source"
          "help:displays the help"
          "info:info returns information about this project"
          "list:list the packages named by the importpaths"
          "test:test packages"
        )
        _describe -t subcommands 'gb subcommands' subcommands && ret=0
      ;;

      (options)
        case $line[1] in
          (build)
            _arguments \
              -f'[ignore cached packages]' \
              -F'[do not cache packages]' \
              -q'[decreases verbosity]' \
              -P'[the number of build jobs to run in parallel]' \
              -R'[sets the base of the project root search path]' \
              -dotfile'[output a dot formatted file of the build steps]' \
              -ldflags'["flag list" arguments to pass to the linker]' \
              -gcflags'["arg list" arguments to pass to the compiler]' \
              -race'[enable data race detection]' \
              -tags'["tag list" additional build tags]'
            ;;
          (list)
            _arguments \
              -f'[alternate format for the list, using the syntax of package template]' \
              -s'[read format template from STDIN]' \
              -json'[prints output in structured JSON format]'
            ;;
          (test)
            _arguments \
              -v'[print output from test subprocess]' \
              -ldflags'["flag list" arguments to pass to the linker]' \
              -gcflags'["arg list" arguments to pass to the compiler]' \
              -race'[enable data race detection]' \
              -tags'["tag list" additional build tags]'
            ;;
        esac
      ;;
    esac

    return ret
}

compdef _gb_commands gb