Expose shell completions scripts in by default in the completion command

[bartekpacia]

Checklist

• Are you running the latest v3 release? The list of releases is here.
• Did you check the manual for your release? The v3 manual is here.
• Did you perform a search about this feature? Here's the GitHub guide about searching.

What problem does this solve?

Makes it easier for developers to add shell completion to the CLI tools they're building with urfave/cli/v3. This would make completion installation the same as the popular Cobra library, that is:

myapp completion zsh prints the completion script for zsh. The user of the CLI gets to decide what to do with it:

• put it into completions directory: `myapp completion zsh > /opt/homebrew/share/zsh/site-functions/_myapp (on macOS), or
• source it in-place: . <(myapp completion zsh)

We already have completion scripts in this repository for all major popular shells (bash, zsh, pwsh), and furthermore, these scripts are already bundled with the module:

cli/completion.go

Lines 14 to 16 in 204d34f

	var (
	//go:embed autocomplete
	autoCompleteFS embed.FS

Solution description

By default, each CLI app made with urfave/cli/v3 should have the completion command (hidden by default)

I don't think this could be brought into v2, because it would break if the developer already defined the completion command.

Describe alternatives you've considered

The alternative is the current situation – developers have to copy , which is unnecessary work, given that the completion files are embedded in urfave/cli anyway.

[dearchap]

@bartekpacia I dont understand. The "generate-completion" is a hidden command in urfave/cli/v3. So if user invokes

myapp generate-completion zsh

It will output the zsh completion script which can be copied by user and sourced.

[bartekpacia]

@dearchap Thank you for pointing it out – I wasn't aware of it.

It doesn't look like this feature is documented anywhere yet – but this may be actually a good thing, because v3 is at alpha, so we could:

• rename default name to completion (to match Cobra - let users use their muscle memory)
• make the completion script not require $PROG to be set – use CLI app name instead.
• write docs! :D

[meatballhat]

@bartekpacia Thank you for bringing this up!

• rename default name to completion (to match Cobra - let users use their muscle memory)

SGTM 👍🏼

• make the completion script not require $PROG to be set – use CLI app name instead.

SGTM 👍🏼

• write docs! :D

SGTM 👍🏼

WDYT about creating targeted issues for each of these?

[bartekpacia]

@meatballhat I think all these changes should be ideally made in a single PR, to keep them atomic and easy to revert - so a single issue to track them is enough for me.

That said if you disagree I can of course create the issues.

[meatballhat]

@bartekpacia Single issue also works for me 👍🏼 I didn't want to pressure you (or anyone else) to get it all done in one shot 😁