Fix high prio recommendations, add error / health screen

text_editor_test.go

@@ -170,6 +170,47 @@ func TestVimTextEditorSubstituteDeletesCharacterAndEntersInsert(t *testing.T) {
 	}
 }
 
+func TestEditorMotionsAndDeletionPreserveGraphemeClusters(t *testing.T) {
+	tests := []struct {
+		name    string
+		cluster string
+	}{
+		{name: "combining mark", cluster: "e\u0301"},
+		{name: "emoji with variation selector", cluster: "❤️"},
+		{name: "multi-code-point emoji", cluster: "👨‍👩‍👧‍👦"},
+		{name: "full-width character", cluster: "界"},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			editor := newTextEditor(test.cluster+"x", true)
+			editor.handleKey(runeKey("l"), true)
+			want := len([]rune(test.cluster))
+			if editor.Cursor != want {
+				t.Fatalf("cursor = %d, want grapheme boundary %d", editor.Cursor, want)
+			}
+			editor.handleKey(runeKey("h"), true)
+			if editor.Cursor != 0 {
+				t.Fatalf("reverse cursor = %d, want 0", editor.Cursor)
+			}
+			editor.handleKey(runeKey("x"), true)
+			if editor.Text != "x" || editor.Cursor != 0 {
+				t.Fatalf("delete split grapheme: text=%q cursor=%d", editor.Text, editor.Cursor)
+			}
+		})
+	}
+}
+
+func TestEditorVisualYankIncludesWholeGrapheme(t *testing.T) {
+	clipboard := &memoryTextClipboard{}
+	editor := newTextEditor("e\u0301x", true)
+	editor.clipboard = clipboard
+	editor.handleKey(runeKey("v"), true)
+	editor.handleKey(runeKey("y"), true)
+	if clipboard.written != "e\u0301" {
+		t.Fatalf("yanked text = %q, want complete combining grapheme", clipboard.written)
+	}
+}
+
 func TestVimTextEditorNormalMotionsStayOnCharactersWithinLine(t *testing.T) {
 	editor := newTextEditor("ab\n  cd\n", true)
 	editor.Cursor = 1