fix(bonfire): end a live view when its context is cancelled and print later lines plainly (WR-09)

modules/bonfire/live_test.go

@@ -655,3 +655,60 @@ func TestNestedProcessBuildsNoProgram(t *testing.T) {
 		t.Errorf("the item's success line is missing:\n%s", ansi.Strip(out.String()))
 	}
 }
+
+// TestPrintAboveAfterCancel (WR-09): cancelling the context given to
+// Process ends its view and unregisters it without waiting for the work
+// function; the lines printed afterwards through Println, Info and
+// bonfire.PrintAbove (which reports false, so the caller prints the line
+// itself, as diary does) are printed plainly once each, none lost.
+func TestPrintAboveAfterCancel(t *testing.T) {
+	out := &lockedBuffer{}
+	c := newConsole(strings.NewReader(""), out, io.Discard, noEnv, boolPtr(true), boolPtr(true))
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	var got []string
+	err := Process(ctx, c, "Pushing", []string{"first", "second", "third"}, func(_ context.Context, item string) error {
+		got = append(got, item)
+		if item != "second" {
+			return nil
+		}
+		cancel()
+		registered := true
+		for deadline := time.Now().Add(2 * time.Second); time.Now().Before(deadline); time.Sleep(5 * time.Millisecond) {
+			liveMu.Lock()
+			registered = activeView != nil
+			liveMu.Unlock()
+			if !registered {
+				break
+			}
+		}
+		if registered {
+			t.Errorf("view still registered 2s after the cancellation")
+		}
+		c.Println("after-cancel-println")
+		c.Info("after-cancel-info")
+		if PrintAbove("after-cancel-printabove") {
+			t.Errorf("PrintAbove reported true after the cancellation")
+		} else {
+			_, _ = io.WriteString(out, "after-cancel-printabove\n")
+		}
+		return nil
+	})
+	if !errors.Is(err, context.Canceled) {
+		t.Errorf("Process returned %v, want context.Canceled", err)
+	}
+	for _, item := range got {
+		if item == "third" {
+			t.Error("fn ran for the item after the cancellation")
+		}
+	}
+	plain := ansi.Strip(out.String())
+	for _, line := range []string{"after-cancel-println", "after-cancel-info", "after-cancel-printabove"} {
+		if n := strings.Count(plain, line); n != 1 {
+			t.Errorf("%q printed %d times, want 1:\n%s", line, n, plain)
+		}
+	}
+	if PrintAbove("after") {
+		t.Error("a view is still registered after Process returned")
+	}
+}