[vidigoat]

What type of PR is this?

• bug

What this PR does / why we need it:

The dynamic shell completion only offers a flag's first name, and after -- it skips a flag whose first name is one letter. So two kinds of flags can't be completed in their long form:

cmd := &cli.Command{
	Name:                  "app",
	EnableShellCompletion: true,
	Flags: []cli.Flag{
		&cli.BoolFlag{Name: "v", Aliases: []string{"verbose"}, Usage: "verbose output"},
		&cli.BoolWithInverseFlag{Name: "color", Usage: "use color"},
	},
	Action: func(context.Context, *cli.Command) error { return nil },
}

In bash 5.3 with bash-completion and the script from app completion bash:

typed	main	with this change
app --ver<TAB>	nothing	--verbose
app --no<TAB>	nothing	--no-color
app --<TAB>	--color --help	--verbose --color --no-color --help

The fish script from ToFishCompletion already offers both, with complete … -s v -l verbose and complete … -l color -l no-color.

• help.go: printFlagSuggestions gets the names to offer from a new completionNames. That is the flag's first name as before, except that after -- a flag whose first name is one letter offers its first long alias (and is still skipped if it has none). A BoolWithInverseFlag also offers the inverse of that name, with its InversePrefix. After a single -, a flag named v is still offered as -v.
• help_test.go: four cases in TestDefaultCompleteWithFlags: the long alias after --; -v still offered after -; --no completing --no-color and --no-dry-run (the inverse of a long alias); and a custom InversePrefix.

Which issue(s) this PR fixes:

None, found while comparing the dynamic completion with the fish script.

Testing

• Three of the new cases fail on main. The -v case passes on both, since it checks what doesn't change.
• Checked in bash 5.3 with bash-completion, as above.
• make all, make test GFLAGS='--tags urfave_cli_no_template', make lint, make diffcheck and make v3diff pass, and so do the urfave_cli_no_docs and urfave_cli_no_suggest tags.
• check-binary-size: the example CLI (linux/amd64, Go 1.27.3, -s -w, minus hello world) goes from 2.261MB to 2.265MB, which still rounds to 2.3MB.

Release Notes

Shell completion now offers the long alias of a flag whose name is one letter after "--", and the inverse form of a BoolWithInverseFlag, such as --no-color.

🤖 Generated with Claude Code