Skip TUI for commands that don't use it (#267)

`PersistentPostRunE` was starting `tea.NewProgram` with
`WithAltScreen` even when the stack was empty, causing a
visible flash for non-interactive commands like object get/put/list.

Author: metonym

cmd/root.go

@@ -52,7 +52,7 @@ var rootCmd = &cobra.Command{
 		output := command.GetFormatFromContext(ctx)
 		if output.Interactive() {
 			stack := tui.GetStackFromContext(ctx)
-			if stack == nil {
+			if stack.IsEmpty() {
 				return nil
 			}
 

pkg/tui/stack.go

@@ -80,6 +80,10 @@ func NewStack() *StackModel {
 	return &StackModel{}
 }
 
+func (m *StackModel) IsEmpty() bool {
+	return m == nil || len(m.stack) == 0
+}
+
 func (m *StackModel) WithDone(f func(tea.Msg) (tea.Model, tea.Cmd)) {
 	m.done = f
 }

pkg/tui/stack_test.go

@@ -15,6 +15,28 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestStackIsEmpty(t *testing.T) {
+	t.Run("returns true for new stack", func(t *testing.T) {
+		stack := tui.NewStack()
+		require.True(t, stack.IsEmpty())
+	})
+
+	t.Run("returns false after push", func(t *testing.T) {
+		stack := tui.NewStack()
+		fooModel := &testhelper.SimpleModel{Str: "foo"}
+		stack.Push(tui.ModelWithCmd{Model: fooModel})
+		require.False(t, stack.IsEmpty())
+	})
+
+	t.Run("returns true after popping all items", func(t *testing.T) {
+		stack := tui.NewStack()
+		fooModel := &testhelper.SimpleModel{Str: "foo"}
+		stack.Push(tui.ModelWithCmd{Model: fooModel})
+		stack.Pop()
+		require.True(t, stack.IsEmpty())
+	})
+}
+
 func TestStack(t *testing.T) {
 	t.Run("Can append and go back", func(t *testing.T) {
 		stack := tui.NewStack()