Implementing application-level aliases (like Git's aliases)

[martinvonz]

Hi,

I'd like to use clap for implementing something very similar to Git's aliases. For example, if the user has configured an alias foo and my command has global option --where=<path> and the user runs cli --where foo foo, I want to replace the second foo by the definition of the alias. This is the reason I want to use clap for this (rather than just replacing the first occurrence of the alias name by its definition).

I was thinking it could be done by defining any global arguments using the Derive API and then doing something like this:

let cli = clap::Command::new("cli").allow_external_subcommands(true);
let cli: clap::Command = GlobalArgs::augment_args(cli);
let matches = cli.get_matches_from(&args);
if let Some((command_name, sub_matches)) = matches.subcommand() {
 // Somehow replace the occurrence of `command_name` in `args`
}
// Re-parse the updated `args` using the full command definition

The question is how I can figure out where in args the command was found. I've found ArgMatches::index_of() but that's documented to not exactly match the argv index.

[edited to clarify why I want to use clap]

[epage]

If its of interest, this is how cargo implements aliases. They basically just treat it as an external subcommand (which is supported via the #[clap(external_subcommand)] alias rather than setting it on the Command) and do a parse with no_binary_name set. This won't provide the absolute best errors but its ok. They manually track global arguments rather than having clap do it so they can use them across the different parse invocations.

[martinvonz]

That looks promising. I think I'd ideally like to allow the aliases to be able to include global arguments in their definitions, but that's what cargo does looks good enough for now at least. Thanks!

[martinvonz]

Actually, it seems I should also be able to handle global arguments in alias definitions using their method.

[epage]

I've created #3679 for adding an example so this will be easier to discover.

[epage]

The question is how I can figure out where in args the command was found. I've found ArgMatches::index_of() but that's documented to not exactly match the argv index.

There is not currently a way to do this though you could open an issue for us to track argv position.

[epage]

If your lookup of aliases is independent of the command line, you could look into replace