command

package module

v0.0.0-...-eabd6fe Latest Latest Go to latest Published: Sep 9, 2025 License: Apache-2.0 Imports: 3 Imported by: 0

Details

see: Partially Implemented

This snippet implements a simple CLI parser that supports a tree of sub-commands.

Input:

a space separated sequence of tokens on a single line
commands and sub-commands start with an alpha [a-zA-z]
flags (tokens starting with a non-alpha, i.e. '-') are allowed.
Registered "command" object that states it's "cli" as a single usage line. See detail below explaining how this usage line is parsed when registering a command.
sub-command tokens take precedence over arguments or parameters. Note that arguments may appear in a command line as a token that starts with an alpha character.

Result (i.e. output): when a command line is passed into the 'parser', the 'parser' returns the proper command object.

The following is an informal, and likely incomplete description of how the usage string is formed.

command sub-command sub-sub-command <arg> [optional-arg] -flag <flag-arg>

commands and sub-commands are always present FIRST in the command line
all commands and sub-commands must be present to match
longest sequence of sub-commands match.
- a sub-command takes precedence over an argument value matching a shorter sub-command.
arguments are matched in order and assigned to a symbol matching the string in the argument. Argument names must start with an alpha
- <argfoo> will be parsed into symbol argfoo
optional arguments must occur after (required) arguments.
flags may be interspersed and begin with one or two dashes
optional flag-args (-f [flag-arg]) are populated in a greedy manner, except if the flag-arg begins with a dash.
- optional flag-args where the command line token begins with a - will be interpreted as the beginning of a new flag and a nul optional value.

The specification above is reasonably complete. The implementation as of this commit is only partially complete.

Command matching works even with parameters that could be in conflict.
Argument (parameter) and Flag population is NOT implemented.
No structures for holding args or flags exist
The return value of Lookup() should be something that has parsed args, flags, and other details of the cmd-line parsing: TBD

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type CommandHandler struct {
	Use     string
	Handler string // a placeholder for a handler function
}

type CommandRegistry interface {
	Register(ch *CommandHandler) error
	Lookup(cmdLine string) (ch *CommandHandler, ok bool)
}

type CommandRepo struct {
	CommandMap map[string]*CommandHandler
}

func NewCommandRegistry() *CommandRepo

func (repo *CommandRepo) Lookup(cmdLine string) (ch *CommandHandler, ok bool)

func (repo *CommandRepo) Register(ch *CommandHandler) error

type DuplicateCommandHandlerError interface {
	error
}