Adds caching to speed up the expression evaluation autocomplete (flutter#3463)

Author: elliette

packages/devtools_app/lib/src/debugger/debugger_controller.dart

@@ -175,6 +175,8 @@ class DebuggerController extends DisposableController
 
   final _showFileOpener = ValueNotifier<bool>(false);
 
+  final _clazzCache = <ClassRef, Class>{};
+
   /// Jump to the given ScriptRef and optional SourcePosition.
   void showScriptLocation(
     ScriptLocation scriptLocation, {
@@ -272,7 +274,7 @@ class DebuggerController extends DisposableController
   /// May return null.
   Future<Class> classFor(ClassRef classRef) async {
     try {
-      return await getObject(classRef);
+      return _clazzCache[classRef] ??= await getObject(classRef);
     } catch (_) {}
     return null;
   }
@@ -840,6 +842,7 @@ class DebuggerController extends DisposableController
   }
 
   void _clearAutocompleteCaches() {
+    _clazzCache.clear();
     libraryMemberAutocompleteCache.clear();
     libraryMemberAndImportsAutocompleteCache.clear();
   }

packages/devtools_app/lib/src/debugger/evaluate.dart

@@ -33,6 +33,9 @@ class _ExpressionEvalFieldState extends State<ExpressionEvalField>
   AutoCompleteController _autoCompleteController;
   int historyPosition = -1;
 
+  String _activeWord = '';
+  List<String> _matches = [];
+
   final evalTextFieldKey = GlobalKey(debugLabel: 'evalTextFieldKey');
 
   @override
@@ -74,7 +77,7 @@ class _ExpressionEvalFieldState extends State<ExpressionEvalField>
       final textFieldEditingValue = searchTextFieldController.value;
       final selection = textFieldEditingValue.selection;
 
-      final parts = AutoCompleteSearchControllerMixin.activeEdtingParts(
+      final parts = AutoCompleteSearchControllerMixin.activeEditingParts(
         searchingValue,
         selection,
         handleFields: isField,
@@ -85,7 +88,14 @@ class _ExpressionEvalFieldState extends State<ExpressionEvalField>
         _autoCompleteController.clearSearchAutoComplete();
         return;
       }
-      final matches = await autoCompleteResultsFor(parts, widget.controller);
+
+      final matches = parts.activeWord.startsWith(_activeWord)
+          ? _filterMatches(_matches, parts.activeWord)
+          : await autoCompleteResultsFor(parts, widget.controller);
+
+      _matches = matches;
+      _activeWord = parts.activeWord;
+
       if (matches.length == 1 && matches.first == parts.activeWord) {
         // It is not useful to show a single autocomplete that is exactly what
         // the already typed.
@@ -180,7 +190,7 @@ class _ExpressionEvalFieldState extends State<ExpressionEvalField>
     final editingValue = textFieldEditingValue.text;
     final selection = textFieldEditingValue.selection;
 
-    final parts = AutoCompleteSearchControllerMixin.activeEdtingParts(
+    final parts = AutoCompleteSearchControllerMixin.activeEditingParts(
       editingValue,
       selection,
       handleFields: _autoCompleteController.search.endsWith('.'),
@@ -200,6 +210,12 @@ class _ExpressionEvalFieldState extends State<ExpressionEvalField>
     );
   }
 
+  List<String> _filterMatches(List<String> previousMatches, String activeWord) {
+    return previousMatches
+        .where((match) => match.startsWith(activeWord))
+        .toList();
+  }
+
   void _handleExpressionEval() async {
     final expressionText = searchTextFieldController.value.text.trim();
     updateSearchField(_autoCompleteController, newValue: '', caretPosition: 0);
@@ -512,10 +528,7 @@ Future<Set<String>> _autoCompleteMembersFor(
   if (classRef == null) {
     return {};
   }
-  // TODO(jacobr): consider using controller.autocompleteCache to cache the list
-  // of autocomplete candidates for each class. The main challenge with caching
-  // is _isAccessible depends on the current source location so makes caching
-  // difficult.
+
   final result = <String>{};
   final clazz = await controller.classFor(classRef);
   if (clazz != null) {

packages/devtools_app/lib/src/ui/search.dart

@@ -473,7 +473,7 @@ mixin AutoCompleteSearchControllerMixin on SearchControllerMixin {
   /// activeWord  is "cl"
   /// leftSide    is "controller."
   /// rightSide   is " + 1000 + myChart.tra"
-  static EditingParts activeEdtingParts(
+  static EditingParts activeEditingParts(
     String editing,
     TextSelection selection, {
     bool handleFields = false,

packages/devtools_app/test/auto_complete_test.dart

@@ -11,7 +11,7 @@ void main() {
     // [caretPosition] if null (default) TextSelection is set to EOL.
     EditingParts testEdit(String editing, [int caretPosition]) {
       final position = caretPosition == null ? editing.length : caretPosition;
-      return AutoCompleteSearchControllerMixin.activeEdtingParts(
+      return AutoCompleteSearchControllerMixin.activeEditingParts(
         editing,
         TextSelection(baseOffset: position, extentOffset: position),
         handleFields: true,