fix(summer): send a delegate's stderr to the root's error writer through bonfire.ErrWriter (IN-13, quick-261028-rqd)

modules/bonfire/root.go

@@ -53,18 +53,26 @@ func OnGlobals(fn func(Globals)) RootOption {
 // It accepts command values rather than a party registry to avoid an import cycle.
 // When out is the process stdout, the error block of Execute goes to stderr.
 func NewRoot(name string, commands []Command, out io.Writer, opts ...RootOption) (*cobra.Command, error) {
-	root, err := NewRootIO(name, commands, os.Stdin, out, out, opts...)
+	root, console, err := newRootIO(name, commands, os.Stdin, out, out, opts...)
 	if err != nil {
 		return nil, err
 	}
 	if out == nil || out == os.Stdout {
 		root.SetErr(os.Stderr)
+		console.errStream = os.Stderr
 	}
 	return root, nil
 }
 
 // NewRootIO is NewRoot with injected stdin/stdout/stderr for tests.
 func NewRootIO(name string, commands []Command, in io.Reader, out, errW io.Writer, opts ...RootOption) (*cobra.Command, error) {
+	root, _, err := newRootIO(name, commands, in, out, errW, opts...)
+	return root, err
+}
+
+// newRootIO builds the root of NewRootIO and returns its console too, so
+// NewRoot can record where it moved the error stream.
+func newRootIO(name string, commands []Command, in io.Reader, out, errW io.Writer, opts ...RootOption) (*cobra.Command, *console, error) {
 	if out == nil {
 		out = os.Stdout
 	}
@@ -84,6 +92,7 @@ func NewRootIO(name string, commands []Command, in io.Reader, out, errW io.Write
 		cfg.version = BuildVersion()
 	}
 	output := newConsole(in, out, errW, os.Getenv, nil, nil)
+	output.errStream = errW
 	root := &cobra.Command{
 		Use:           name,
 		SilenceUsage:  true,
@@ -116,24 +125,24 @@ func NewRootIO(name string, commands []Command, in io.Reader, out, errW io.Write
 	}
 	for _, command := range commands {
 		if seen[command.Name] {
-			return nil, fmt.Errorf("%w: %q", ErrDuplicateCommand, command.Name)
+			return nil, nil, fmt.Errorf("%w: %q", ErrDuplicateCommand, command.Name)
 		}
 		seen[command.Name] = true
 		cmd, err := st.wrap(command, true)
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 		root.AddCommand(cmd)
 	}
 
 	listCmd, err := st.wrap(st.listCommand(), false)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	root.AddCommand(listCmd)
 	helpCmd, err := st.wrap(st.helpCommand(), false)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	root.SetHelpCommand(helpCmd)
 	root.SetHelpFunc(func(*cobra.Command, []string) {
@@ -160,7 +169,7 @@ func NewRootIO(name string, commands []Command, in io.Reader, out, errW io.Write
 		}
 		return nil
 	}
-	return root, nil
+	return root, output, nil
 }
 
 // rootState is what the list, help and error rendering of one root share.