kittens: Fix errors not being reported to user when run a UI kitten

Fixes #6403

tools/cli/command.go

@@ -39,6 +39,8 @@ type Command struct {
 	IgnoreAllArgs bool
 	// Specialised arg parsing
 	ParseArgsForCompletion func(cmd *Command, args []string, completions *Completions)
+	// Callback that is called on error
+	CallbackOnError func(cmd *Command, err error, during_parsing bool, exit_code int) (final_exit_code int)
 
 	SubCommandGroups []*CommandGroup
 	OptionGroups     []*OptionGroup
@@ -529,6 +531,9 @@ func (self *Command) ExecArgs(args []string) (exit_code int) {
 	}
 	cmd, err := root.ParseArgs(args)
 	if err != nil {
+		if self.CallbackOnError != nil {
+			return self.CallbackOnError(cmd, err, true, 1)
+		}
 		ShowError(err)
 		return 1
 	}
@@ -543,10 +548,13 @@ func (self *Command) ExecArgs(args []string) (exit_code int) {
 	} else if cmd.Run != nil {
 		exit_code, err = cmd.Run(cmd, cmd.Args)
 		if err != nil {
-			ShowError(err)
 			if exit_code == 0 {
 				exit_code = 1
 			}
+			if self.CallbackOnError != nil {
+				return self.CallbackOnError(cmd, err, false, exit_code)
+			}
+			ShowError(err)
 		}
 	}
 	return

tools/cmd/tool/main.go

@@ -30,6 +30,7 @@ var _ = fmt.Print
 func KittyToolEntryPoints(root *cli.Command) {
 	root.Add(cli.OptionSpec{
 		Name: "--version", Type: "bool-set", Help: "The current kitten version."})
+	tui.PrepareRootCmd(root)
 	// @
 	at.EntryPoint(root)
 	// update-self

tools/tui/ui_kitten.go

@@ -15,9 +15,22 @@ import (
 
 var _ = fmt.Print
 
+var RunningAsUI = utils.Once(func() bool {
+	defer func() { os.Unsetenv("KITTEN_RUNNING_AS_UI") }()
+	return os.Getenv("KITTEN_RUNNING_AS_UI") != ""
+})
+
+func PrepareRootCmd(root *cli.Command) {
+	if RunningAsUI() {
+		root.CallbackOnError = func(cmd *cli.Command, err error, during_parsing bool, exit_code int) int {
+			ReportError(err)
+			return exit_code
+		}
+	}
+}
+
 func KittenOutputSerializer() func(any) (string, error) {
-	write_with_escape_code := os.Getenv("KITTEN_RUNNING_AS_UI") != ""
-	os.Unsetenv("KITTEN_RUNNING_AS_UI")
+	write_with_escape_code := RunningAsUI()
 	if write_with_escape_code {
 		return func(what any) (string, error) {
 			data, err := json.Marshal(what)