refactor(completion): name path arguments explicitly and share firstArg

The six commands that take a file or directory argument set their
completer directly instead of a Use-line parser wrapping every
command, the first-argument-only wrappers become one firstArg helper,
and only the bash completion help keeps a custom text.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/completion.go

@@ -519,9 +519,9 @@ func actionScope(scope func() services.ActionScope, t target) services.ActionSco
 // pathFlags take local file paths, like every flag whose name ends in -file.
 var pathFlags = []string{"asset", "attachment", "file", "input", "ssh-key"}
 
-// completeDefaults completes paths only where a command takes them: path flags, flags marked with
-// MarkFlagFilename, and positional arguments named file or directory in Use. Everything else without a
-// completer completes nothing, by the root's default directive, rather than file names.
+// completeDefaults completes paths only where a command takes them: path flags and flags marked
+// with MarkFlagFilename. Everything else without a completer completes nothing, by the root's
+// default directive, rather than file names.
 func completeDefaults(cmd *cobra.Command) {
 	for _, flags := range []*pflag.FlagSet{cmd.Flags(), cmd.PersistentFlags()} {
 		flags.VisitAll(func(flag *pflag.Flag) {
@@ -536,23 +536,6 @@ func completeDefaults(cmd *cobra.Command) {
 			}
 		})
 	}
-	if slots := argSlots(cmd.Use); len(slots) > 0 {
-		complete := cmd.ValidArgsFunction
-		cmd.ValidArgsFunction = func(c *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
-			slot := slots[min(len(args), len(slots)-1)]
-			switch {
-			case len(args) >= len(slots) && !slot.variadic:
-				return nil, cobra.ShellCompDirectiveNoFileComp
-			case slot.kind == "file":
-				return completeFiles(c, args, toComplete)
-			case slot.kind == "directory":
-				return completeDirectories(c, args, toComplete)
-			case complete != nil:
-				return complete(c, args, toComplete)
-			}
-			return nil, cobra.ShellCompDirectiveNoFileComp
-		}
-	}
 	for _, child := range cmd.Commands() {
 		completeDefaults(child)
 	}
@@ -568,89 +551,53 @@ func completeDirectories(*cobra.Command, []string, string) ([]cobra.Completion,
 	return nil, cobra.ShellCompDirectiveFilterDirs
 }
 
-// argSlot is one positional argument that a Use line declares, such as <number>, [directory] or
-// <file>...; kind is "file" or "directory" for path arguments.
-type argSlot struct {
-	kind     string
-	variadic bool
-}
-
-// argSlots parses the positional arguments of a Use line.
-func argSlots(use string) []argSlot {
-	_, rest, _ := strings.Cut(use, " ")
-	var slots []argSlot
-	depth, start := 0, 0
-	for i, r := range rest {
-		switch r {
-		case '<', '[', '{':
-			if depth == 0 {
-				start = i
-			}
-			depth++
-		case '>', ']', '}':
-			if depth--; depth != 0 {
-				continue
-			}
-			slot := argSlot{variadic: strings.HasPrefix(rest[i+1:], "...") || strings.HasSuffix(rest[start:i], "...")}
-			for name := range strings.FieldsFuncSeq(rest[start:i+1], func(r rune) bool { return strings.ContainsRune("<>[]|. ", r) }) {
-				switch {
-				case name == "file" || strings.HasSuffix(name, "-file"):
-					slot.kind = "file"
-				case name == "directory" || name == "dir":
-					slot.kind = "directory"
-				}
-			}
-			slots = append(slots, slot)
+// firstArg completes only the first argument with complete.
+func firstArg(complete cobra.CompletionFunc) cobra.CompletionFunc {
+	return func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
+		if len(args) > 0 {
+			return nil, cobra.ShellCompDirectiveNoFileComp
 		}
+		return complete(cmd, args, toComplete)
 	}
-	return slots
 }
 
-// completionInstallHelp explains how to load the completion scripts, including with macOS's bash 3.2
-// and in zsh without compinit.
+// pathArgs completes the arguments before position n with complete, and paths with path from
+// position n on: every later argument when variadic, else only the one at n.
+func pathArgs(n int, variadic bool, path, complete cobra.CompletionFunc) cobra.CompletionFunc {
+	return func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
+		switch {
+		case len(args) < n:
+			return complete(cmd, args, toComplete)
+		case len(args) == n || variadic:
+			return path(cmd, args, toComplete)
+		}
+		return nil, cobra.ShellCompDirectiveNoFileComp
+	}
+}
+
+// completionInstallHelp explains how to load the bash script with macOS's bash 3.2, which cannot
+// source <(tea completion bash); cobra's help covers the other shells.
 func completionInstallHelp(root *cobra.Command) {
 	completion, _, err := root.Find([]string{"completion"})
 	if err != nil || completion == root {
 		return
 	}
 	completion.Short = "Generate shell completion scripts"
-	completion.Long = `Generate shell completion scripts for tea.
-
-Completion offers commands, flags, flag values such as --state or --json fields, and values
-from the selected instance, such as repositories, issue numbers and labels. See
-tea completion <shell> --help for how to load the script in your shell.`
-	help := map[string][2]string{
-		"bash": {`Generate the completion script for bash.
-
-The script needs the bash-completion package. On macOS, install bash-completion with
-Homebrew for the system bash 3.2, or bash-completion@2 for a Homebrew bash, and load it
-as its install notes say.
-
-To load completions in every new shell, add the eval line below to ~/.bashrc (on macOS,
-~/.bash_profile). Use eval: bash 3.2, the default on macOS, cannot source <(tea completion bash).`, `# Load completions in this shell, or in every shell from ~/.bashrc
-$ eval "$(tea completion bash)"
-# Or install the script for every user (Linux, then macOS)
-$ tea completion bash > /etc/bash_completion.d/tea
-$ tea completion bash > "$(brew --prefix)/etc/bash_completion.d/tea"`},
-		"zsh": {`Generate the completion script for zsh.
-
-Completion must be initialized before the script loads: add these lines to ~/.zshrc,
-keeping an existing compinit call instead of the first line. Without compinit, zsh
-reports "command not found: compdef".`, `$ autoload -U compinit && compinit
-$ source <(tea completion zsh)
-# Or install the script into a directory of your fpath once
-$ tea completion zsh > "${fpath[1]}/_tea"`},
-		"fish": {`Generate the completion script for fish.
-
-To load completions in every new shell, install the script once.`, `$ tea completion fish > ~/.config/fish/completions/tea.fish`},
-		"powershell": {`Generate the completion script for PowerShell.
-
-To load completions in every new shell, add this line to your PowerShell profile.`, `$ tea completion powershell | Out-String | Invoke-Expression`},
+	examples := map[string]string{
+		"bash":       `$ eval "$(tea completion bash)"`,
+		"zsh":        `$ source <(tea completion zsh)`,
+		"fish":       `$ tea completion fish > ~/.config/fish/completions/tea.fish`,
+		"powershell": `$ tea completion powershell | Out-String | Invoke-Expression`,
 	}
 	for _, shell := range completion.Commands() {
-		shell.Long, shell.Example = help[shell.Name()][0], help[shell.Name()][1]
+		shell.Example = examples[shell.Name()]
 		if flag := shell.Flags().Lookup("no-descriptions"); flag != nil {
 			flag.Usage = "Disable completion descriptions"
 		}
 	}
+	bash, _, _ := completion.Find([]string{"bash"})
+	bash.Long = `Generate the completion script for bash. It needs the bash-completion package.
+
+To load completions in every new shell, add the eval line below to ~/.bashrc (on macOS,
+~/.bash_profile); bash 3.2, the default on macOS, cannot source <(tea completion bash).`
 }