selection: Add PreSelected option to multi selection

.assets/generate.py

@@ -65,7 +65,12 @@ def process_tape(tape: Path) -> str:
 
 
 def main() -> None:
-    tapes = sorted(ASSETS_DIR.glob("*.tape"))
+    selector = (
+        "*.tape" if sys.argv == 0 else sys.argv[1].removesuffix(".tape") + ".tape"
+    )
+    print(selector)
+
+    tapes = sorted(ASSETS_DIR.glob(selector))
     if not tapes:
         print("No .tape files found in", ASSETS_DIR)
         sys.exit(1)

.assets/multi_selection_custom.tape

@@ -8,7 +8,7 @@ Set Height 600
 Type@30ms "./examples/multi_selection_custom"
 Sleep 100ms  Enter
 Sleep 1s
-Space
+Down Sleep 250ms
 Down Sleep 250ms
 Space
 Sleep 1

examples/multi_selection_custom/main.go

@@ -30,9 +30,9 @@ func main() {
 	}
 
 	choices := []lang{
+		{name: "Python", icon: "🐍"},
 		{name: "Go", icon: "🐹"},
 		{name: "Rust", icon: "🦀"},
-		{name: "Python", icon: "🐍"},
 		{name: "TypeScript", icon: "📘"},
 		{name: "Haskell", icon: "λ"},
 	}
@@ -44,6 +44,7 @@ func main() {
 	sp.MinSelections = 2
 	sp.MaxSelections = 4
 	sp.LoopCursor = true
+	sp.PreSelected = selection.PreSelect(choices[1])
 
 	// Custom styling with emoji icons.
 	sp.UnmarkedChoiceStyle = func(c *selection.Choice[lang]) string {

selection/multi_model.go

@@ -81,7 +81,16 @@ func (m *MultiModel[T]) Init() tea.Cmd {
 	}
 
 	m.filterInput = m.initFilterInput()
+
 	m.selectedChoices = make(map[int]bool)
+	if m.PreSelected != nil {
+		for _, c := range m.choices {
+			if m.PreSelected(c) {
+				m.selectedChoices[c.idx] = true
+			}
+		}
+	}
+
 	m.currentChoices, m.availableChoices = m.filteredAndPagedChoices()
 	m.requestedPageSize = m.PageSize
 

selection/multi_model_test.go

@@ -392,6 +392,33 @@ func TestMultiZeroMinSelections(t *testing.T) {
 	}
 }
 
+func TestMultiPreSelect(t *testing.T) {
+	t.Parallel()
+
+	m := selection.NewMultiModel(selection.NewMulti("foo:", []string{"a", "b", "c"}))
+	m.ColorProfile = termenv.TrueColor
+	m.PageSize = 2
+	m.PreSelected = selection.PreSelect("b", "c")
+
+	test.Run(t, m)
+	test.AssertGoldenView(t, m, "multi_preselect_pre.golden")
+
+	values := getValues(t, m)
+	if len(values) != 2 || values[0] != "b" || values[1] != "c" {
+		t.Fatalf("selected values are not b and c: %#v", values)
+	}
+
+	test.Update(t, m, keySpace)
+
+	values = getValues(t, m)
+	if len(values) != 3 || values[0] != "a" || values[1] != "b" || values[2] != "c" {
+		t.Fatalf("selected values are not a, b and c: %#v", values)
+	}
+
+	test.Update(t, m, keyEnter)
+	test.AssertGoldenView(t, m, "multi_preselect_post.golden")
+}
+
 var keyEsc = tea.KeyPressMsg{Code: tea.KeyEsc}
 
 func getValues[T any](tb testing.TB, m *selection.MultiModel[T]) []T {

selection/multi_prompt.go

@@ -101,6 +101,11 @@ type MultiSelection[T any] struct {
 	// disabled and FilterPlaceholder does nothing.
 	FilterPlaceholder string
 
+	// PreSelected is an optional function that decided whether an option should
+	// be pre-selected. It can easily be populated from a single choice value or
+	// a slice of choice values using the selection.PreSelected helper.
+	PreSelected func(c *Choice[T]) bool
+
 	// PageSize is the number of choices that are displayed at once. If
 	// PageSize is smaller than the number of choices, pagination is enabled.
 	// If PageSize is 0, pagination is disabled. Regardless of the value of
@@ -286,3 +291,19 @@ func (s *MultiSelection[T]) RunPrompt() ([]T, error) {
 
 	return m.Values()
 }
+
+func PreSelect[T comparable](preSelectedValues ...T) func(c *Choice[T]) bool {
+	if len(preSelectedValues) == 0 {
+		return nil
+	}
+
+	preSelectedMap := map[T]bool{}
+
+	for _, v := range preSelectedValues {
+		preSelectedMap[v] = true
+	}
+
+	return func(c *Choice[T]) bool {
+		return preSelectedMap[c.Value]
+	}
+}

selection/testdata/multi_preselect_post.golden

@@ -0,0 +1 @@
+foo: a, b, c

selection/testdata/multi_preselect_pre.golden

@@ -0,0 +1,5 @@
+foo:
+Filter: Type to filter choices                                                           
+  ▸ ☐ a
+⇣   ☑ b
+  ☑ c