fix(tui): offer local command completion before kernel replies

internal/frontend/tui/complete.go

@@ -1,6 +1,7 @@
 package tui
 
 import (
+	"slices"
 	"strings"
 	"unicode/utf16"
 	"unicode/utf8"
@@ -85,14 +86,17 @@ func (m *model) refreshMenu() tea.Cmd {
 		m.menu = nil
 		return nil
 	}
+	m.onCompletion(completionMsg{line: line})
 	return m.fetchCompletion()
 }
 
 func (m *model) onCompletion(msg completionMsg) {
-	if msg.err != nil || msg.line != m.composer.Value() {
-		m.menu = nil
+	if msg.line != m.composer.Value() {
 		return
 	}
+	if msg.err != nil {
+		msg.c = Completion{}
+	}
 	c := msg.c
 	c.Items = append(m.localCommands(msg.line), c.Items...)
 	if c.Typed != nil {
@@ -105,7 +109,11 @@ func (m *model) onCompletion(msg completionMsg) {
 	if len(msg.c.Items) == 0 {
 		c.From, c.To = 0, utf16At(msg.line, len(msg.line))
 	}
-	m.menu = &menu{line: msg.line, c: c}
+	sel := 0
+	if m.menu != nil && m.menu.line == msg.line {
+		sel = max(0, slices.Index(c.Items, m.menu.c.Items[m.menu.sel]))
+	}
+	m.menu = &menu{line: msg.line, c: c, sel: sel}
 }
 
 // localCommands are the slash commands this screen answers itself, offered
@@ -145,7 +153,8 @@ func (m *model) localCommands(line string) []CompletionItem {
 
 // menuKey takes the keys an open menu owns.
 func (m *model) menuKey(k string) (tea.Cmd, bool) {
-	if m.menu == nil {
+	if m.menu == nil || m.menu.line != m.composer.Value() {
+		m.menu = nil
 		return nil, false
 	}
 	n := len(m.menu.c.Items)
@@ -201,7 +210,7 @@ func (m *model) acceptCompletion() tea.Cmd {
 }
 
 func (m *model) menuLines() []string {
-	if m.menu == nil {
+	if m.menu == nil || m.menu.line != m.composer.Value() {
 		return nil
 	}
 	items := m.menu.c.Items

internal/frontend/tui/complete_local_test.go

@@ -0,0 +1,84 @@
+package tui
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	tea "charm.land/bubbletea/v2"
+)
+
+func TestTabCompletesLocalCommandsBeforeAnyKernelReply(t *testing.T) {
+	for _, tc := range []struct{ typed, want string }{
+		{"/resu", "/resume"},
+		{"/ver", "/version"},
+		{"/cop", "/copy"},
+	} {
+		t.Run(tc.typed, func(t *testing.T) {
+			m, k := testModel(t)
+			typeText(m, tc.typed)
+			m.Update(tea.KeyPressMsg{Code: tea.KeyTab})
+			if got := m.composer.Value(); got != tc.want {
+				t.Fatalf("composer after immediate Tab = %q, want %q", got, tc.want)
+			}
+			if calledWith(k, "GET /complete") {
+				t.Fatal("local completion waited for a kernel request")
+			}
+		})
+	}
+}
+
+func TestStaleKernelCompletionKeepsTheCurrentLocalMenu(t *testing.T) {
+	m, _ := testModel(t)
+	_, old := m.Update(tea.KeyPressMsg{Code: '/', Text: "/"})
+	typeText(m, "resu")
+	run(m, old)
+	m.Update(tea.KeyPressMsg{Code: tea.KeyTab})
+	if got := m.composer.Value(); got != "/resume" {
+		t.Fatalf("composer after stale reply and Tab = %q, want /resume", got)
+	}
+}
+
+func TestKernelReplyKeepsTheHighlightedLocalCommand(t *testing.T) {
+	m, _ := testModel(t)
+	_, pending := m.Update(tea.KeyPressMsg{Code: '/', Text: "/"})
+	press(m, "down")
+	run(m, pending)
+	m.Update(tea.KeyPressMsg{Code: tea.KeyTab})
+	if got := m.composer.Value(); got != "/queue" {
+		t.Fatalf("composer after Down, reply, Tab = %q, want /queue", got)
+	}
+}
+
+func TestLocalCompletionSurvivesAKernelFailure(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusServiceUnavailable)
+	}))
+	t.Cleanup(srv.Close)
+	m := newModel(context.Background(), Options{Client: &Client{HTTP: srv.Client(), Base: srv.URL}})
+	m.Update(tea.WindowSizeMsg{Width: 80, Height: 24})
+	typeText(m, "/res")
+	_, cmd := m.Update(tea.KeyPressMsg{Code: 'u', Text: "u"})
+	run(m, cmd)
+	m.Update(tea.KeyPressMsg{Code: tea.KeyTab})
+	if got := m.composer.Value(); got != "/resume" {
+		t.Fatalf("composer after failed lookup and Tab = %q, want /resume", got)
+	}
+}
+
+func TestTabAfterClearingDoesNotAcceptThePreviousMenu(t *testing.T) {
+	m, _ := testModel(t)
+	typeText(m, "/resu")
+	press(m, "ctrl+c")
+	if rows := m.menuLines(); len(rows) != 0 {
+		t.Fatalf("the cleared input still shows its old menu: %v", rows)
+	}
+	_, cmd := m.Update(tea.KeyPressMsg{Code: tea.KeyTab})
+	if got := m.composer.Value(); got != "" {
+		t.Fatalf("Tab restored the cleared command: %q", got)
+	}
+	if cmd == nil {
+		t.Fatal("Tab did not request completions for the cleared input")
+	}
+}