feat: implement Minimum to MultiSelect

field_multiselect.go

@@ -27,6 +27,7 @@ type MultiSelect[T comparable] struct {
 	filterable      bool
 	filteredOptions []Option[T]
 	limit           int
+	minimum         int
 	height          int
 
 	// error handling
@@ -174,6 +175,12 @@ func (m *MultiSelect[T]) Limit(limit int) *MultiSelect[T] {
 	return m
 }
 
+// Minimum sets the minimum of the multi-select field.
+func (m *MultiSelect[T]) Minimum(minimum int) *MultiSelect[T] {
+	m.minimum = minimum
+	return m
+}
+
 // Height sets the height of the multi-select field.
 func (m *MultiSelect[T]) Height(height int) *MultiSelect[T] {
 	// What we really want to do is set the height of the viewport, but we
@@ -379,13 +386,21 @@ func (m *MultiSelect[T]) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			m.updateValue()
 		case key.Matches(msg, m.keymap.Prev):
 			m.updateValue()
+			if m.minimum > 0 && m.numSelected() < m.minimum {
+				m.err = fmt.Errorf("you must select at least %d options", m.minimum)
+				return m, nil
+			}
 			m.err = m.validate(m.accessor.Get())
 			if m.err != nil {
 				return m, nil
 			}
 			return m, PrevField
 		case key.Matches(msg, m.keymap.Next, m.keymap.Submit):
 			m.updateValue()
+			if m.minimum > 0 && m.numSelected() < m.minimum {
+				m.err = fmt.Errorf("you must select at least %d options", m.minimum)
+				return m, nil
+			}
 			m.err = m.validate(m.accessor.Get())
 			if m.err != nil {
 				return m, nil

huh_test.go

@@ -28,8 +28,13 @@ func TestForm(t *testing.T) {
 		Toppings []string
 	}
 
+	type Beverages struct {
+		Name []string
+	}
+
 	type Order struct {
 		Taco         Taco
+		Beverages    Beverages
 		Name         string
 		Instructions string
 		Discount     bool
@@ -83,6 +88,24 @@ func TestForm(t *testing.T) {
 				Limit(4),
 		),
 
+		// Prompt for beverages.
+		// The customer can ask for at least two beverages.
+		NewGroup(
+			NewMultiSelect[string]().
+				Title("Beverages").
+				Description("Choose at least two.").
+				Options(
+					NewOption("Coke", "coke").Selected(true),
+					NewOption("Pepsi", "pepsi").Selected(true),
+					NewOption("Sprite", "sprite"),
+					NewOption("Fanta", "fanta"),
+					NewOption("Dr. Pepper", "dr. pepper"),
+				).
+				Value(&order.Beverages.Name).
+				Filterable(true).
+				Minimum(2),
+		),
+
 		// Gather final details for the order.
 		NewGroup(
 			NewInput().
@@ -219,6 +242,40 @@ func TestForm(t *testing.T) {
 	m = batchUpdate(m.Update(tea.KeyMsg{Type: tea.KeyEnter}))
 	view = ansi.Strip(m.View())
 
+	//
+	// ┃ Beverages
+	// ┃ Choose at least two.
+	// ┃ > ✓ Coke
+	// ┃   ✓ Pepsi
+	// ┃   • Sprite
+	// ┃   • Fanta
+	// ┃   • Dr. Pepper
+	//
+	//  x toggle • ↑ up • ↓ down • enter confirm • shift+tab back
+	//
+	if !strings.Contains(view, "Beverages") {
+		t.Log(pretty.Render(view))
+		t.Fatal("Expected form to show beverages group")
+	}
+
+	if !strings.Contains(view, "Choose at least two.") {
+		t.Log(pretty.Render(view))
+		t.Error("Expected form to show beverages description")
+	}
+
+	if !strings.Contains(view, "> ✓ Coke") {
+		t.Log(pretty.Render(view))
+		t.Error("Expected form to preselect coke")
+	}
+
+	if !strings.Contains(view, "  ✓ Pepsi") {
+		t.Log(pretty.Render(view))
+		t.Error("Expected form to preselect pepsi")
+	}
+
+	m = batchUpdate(m.Update(tea.KeyMsg{Type: tea.KeyEnter}))
+	view = ansi.Strip(m.View())
+
 	if !strings.Contains(view, "What's your name?") {
 		t.Log(pretty.Render(view))
 		t.Error("Expected form to prompt for name")