Deoptimize Search - request a new resolved unit for local search.

It seems to me that it would be easier to integrate if we keep the
same search technique - search for Element references. I think any
saving can be only for local elements search. If it turns out to
be expensive, we could add priority results caching in the driver.

R=brianwilkerson@google.com
BUG=

Review URL: https://codereview.chromium.org/2521913004 .

pkg/analyzer/lib/src/dart/analysis/search.dart

@@ -21,47 +21,46 @@ class Search {
   Search(this._driver);
 
   /**
-   * Returns references to the element at the given [offset] in the file with
-   * the given [path].
+   * Returns references to the [element].
    */
-  Future<List<SearchResult>> references(String path, int offset) async {
-    // Search only in added files.
-    if (!_driver.addedFiles.contains(path)) {
-      return const <SearchResult>[];
-    }
-
-    AnalysisResult analysisResult = await _driver.getResult(path);
-    CompilationUnit unit = analysisResult.unit;
-
-    // Prepare the node.
-    AstNode node = new NodeLocator(offset).searchWithin(unit);
-    if (node == null) {
-      return const <SearchResult>[];
-    }
-
-    // Prepare the element.
-    Element element = ElementLocator.locate(node);
+  Future<List<SearchResult>> references(Element element) async {
     if (element == null) {
       return const <SearchResult>[];
     }
 
     ElementKind kind = element.kind;
     if (kind == ElementKind.LABEL || kind == ElementKind.LOCAL_VARIABLE) {
-      Block block = node.getAncestor((n) => n is Block);
-      return _searchReferences_Local(element, unit.element, block);
+      return _searchReferences_Local(element, (n) => n is Block);
     }
     // TODO(scheglov) support other kinds
-    return [];
+    return const <SearchResult>[];
   }
 
   Future<List<SearchResult>> _searchReferences_Local(
-      Element element,
-      CompilationUnitElement enclosingUnitElement,
-      AstNode enclosingNode) async {
+      Element element, bool isRootNode(AstNode n)) async {
+    String path = element.source.fullName;
+
+    // Prepare the unit.
+    AnalysisResult analysisResult = await _driver.getResult(path);
+    CompilationUnit unit = analysisResult.unit;
+    if (unit == null) {
+      return const <SearchResult>[];
+    }
+
+    // Prepare the node.
+    AstNode node = new NodeLocator(element.nameOffset).searchWithin(unit);
+    if (node == null) {
+      return const <SearchResult>[];
+    }
+
+    // Prepare the enclosing node.
+    AstNode enclosingNode = node.getAncestor(isRootNode);
+
+    // Find the matches.
     _LocalReferencesVisitor visitor =
-        new _LocalReferencesVisitor(element, enclosingUnitElement);
-    enclosingNode?.accept(visitor);
-    return visitor.matches;
+        new _LocalReferencesVisitor(element, unit.element);
+    enclosingNode.accept(visitor);
+    return visitor.results;
   }
 }
 
@@ -159,7 +158,7 @@ class _ContainingElementFinder extends GeneralizingElementVisitor {
  * type parameters, import prefixes.
  */
 class _LocalReferencesVisitor extends RecursiveAstVisitor {
-  final List<SearchResult> matches = <SearchResult>[];
+  final List<SearchResult> results = <SearchResult>[];
 
   final Element element;
   final CompilationUnitElement enclosingUnitElement;
@@ -193,15 +192,15 @@ class _LocalReferencesVisitor extends RecursiveAstVisitor {
           kind = SearchResultKind.WRITE;
         }
       }
-      _addMatch(node, kind);
+      _addResult(node, kind);
     }
   }
 
-  void _addMatch(AstNode node, SearchResultKind kind) {
+  void _addResult(AstNode node, SearchResultKind kind) {
     bool isQualified = node.parent is Label;
     var finder = new _ContainingElementFinder(node.offset);
     enclosingUnitElement.accept(finder);
-    matches.add(new SearchResult._(element, finder.containingElement, kind,
+    results.add(new SearchResult._(element, finder.containingElement, kind,
         node.offset, node.length, true, isQualified));
   }
 }

pkg/analyzer/test/src/dart/analysis/base.dart

@@ -4,6 +4,8 @@
 
 import 'dart:async';
 
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/visitor.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/source/package_map_resolver.dart';
@@ -17,6 +19,30 @@ import 'package:test/test.dart';
 
 import '../../context/mock_sdk.dart';
 
+/**
+ * Finds an [Element] with the given [name].
+ */
+Element findChildElement(Element root, String name, [ElementKind kind]) {
+  Element result = null;
+  root.accept(new _ElementVisitorFunctionWrapper((Element element) {
+    if (element.name != name) {
+      return;
+    }
+    if (kind != null && element.kind != kind) {
+      return;
+    }
+    result = element;
+  }));
+  return result;
+}
+
+typedef bool Predicate<E>(E argument);
+
+/**
+ * A function to be called for every [Element].
+ */
+typedef void _ElementVisitorFunction(Element element);
+
 class BaseAnalysisDriverTest {
   static final MockSdk sdk = new MockSdk();
 
@@ -108,6 +134,20 @@ class BaseAnalysisDriverTest {
   String _p(String path) => provider.convertPath(path);
 }
 
+/**
+ * Wraps an [_ElementVisitorFunction] into a [GeneralizingElementVisitor].
+ */
+class _ElementVisitorFunctionWrapper extends GeneralizingElementVisitor {
+  final _ElementVisitorFunction function;
+
+  _ElementVisitorFunctionWrapper(this.function);
+
+  visitElement(Element element) {
+    function(element);
+    super.visitElement(element);
+  }
+}
+
 class _Monitor {
   Completer<Null> _completer = new Completer<Null>();
 

pkg/analyzer/test/src/dart/analysis/index_test.dart

@@ -7,7 +7,6 @@ import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
-import 'package:analyzer/dart/element/visitor.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/dart/analysis/index.dart';
 import 'package:analyzer/src/summary/format.dart';
@@ -23,28 +22,6 @@ main() {
   });
 }
 
-/**
- * Finds an [Element] with the given [name].
- */
-Element findChildElement(Element root, String name, [ElementKind kind]) {
-  Element result = null;
-  root.accept(new _ElementVisitorFunctionWrapper((Element element) {
-    if (element.name != name) {
-      return;
-    }
-    if (kind != null && element.kind != kind) {
-      return;
-    }
-    result = element;
-  }));
-  return result;
-}
-
-/**
- * A function to be called for every [Element].
- */
-typedef void _ElementVisitorFunction(Element element);
-
 class ExpectedLocation {
   final CompilationUnitElement unitElement;
   final int offset;
@@ -1210,20 +1187,6 @@ class _ElementIndexAssert {
   }
 }
 
-/**
- * Wraps an [_ElementVisitorFunction] into a [GeneralizingElementVisitor].
- */
-class _ElementVisitorFunctionWrapper extends GeneralizingElementVisitor {
-  final _ElementVisitorFunction function;
-
-  _ElementVisitorFunctionWrapper(this.function);
-
-  visitElement(Element element) {
-    function(element);
-    super.visitElement(element);
-  }
-}
-
 class _NameIndexAssert {
   final IndexTest test;
   final String name;

pkg/analyzer/test/src/dart/analysis/search_test.dart

@@ -4,8 +4,11 @@
 
 import 'dart:async';
 
+import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/dart/analysis/search.dart';
+import 'package:analyzer/src/dart/ast/utilities.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ -90,13 +93,13 @@ label:
   }
 }
 ''');
-    int offset = findOffset('label:');
+    Element element = await _findElementAtString('label:');
     List<String> main = [testUri, 'main'];
     var expected = [
       _expectId(main, SearchResultKind.REFERENCE, 'label; // 1'),
       _expectId(main, SearchResultKind.REFERENCE, 'label; // 2')
     ];
-    await _verifyReferences(offset, expected);
+    await _verifyReferences(element, expected);
   }
 
   test_searchReferences_localVariable() async {
@@ -109,7 +112,7 @@ main() {
   v();
 }
 ''');
-    int offset = findOffset('v;');
+    Element element = await _findElementAtString('v;');
     List<String> main = [testUri, 'main'];
     var expected = [
       _expectId(main, SearchResultKind.WRITE, 'v = 1;'),
@@ -117,7 +120,7 @@ main() {
       _expectId(main, SearchResultKind.READ, 'v);'),
       _expectId(main, SearchResultKind.INVOCATION, 'v();')
     ];
-    await _verifyReferences(offset, expected);
+    await _verifyReferences(element, expected);
   }
 
   test_searchReferences_localVariable_inForEachLoop() async {
@@ -131,7 +134,7 @@ main() {
   }
 }
 ''');
-    int offset = findOffset('v in []');
+    Element element = await _findElementAtString('v in []');
     List<String> main = [testUri, 'main'];
     var expected = [
       _expectId(main, SearchResultKind.WRITE, 'v = 1;'),
@@ -139,7 +142,7 @@ main() {
       _expectId(main, SearchResultKind.READ, 'v);'),
       _expectId(main, SearchResultKind.INVOCATION, 'v();')
     ];
-    await _verifyReferences(offset, expected);
+    await _verifyReferences(element, expected);
   }
 
   ExpectedResult _expectId(
@@ -153,10 +156,16 @@ main() {
         isResolved: isResolved, isQualified: isQualified);
   }
 
+  Future<Element> _findElementAtString(String search) async {
+    AnalysisResult result = await driver.getResult(testFile);
+    int offset = findOffset(search);
+    AstNode node = new NodeLocator(offset).searchWithin(result.unit);
+    return ElementLocator.locate(node);
+  }
+
   Future _verifyReferences(
-      int offset, List<ExpectedResult> expectedMatches) async {
-    List<SearchResult> results =
-        await driver.search.references(testFile, offset);
+      Element element, List<ExpectedResult> expectedMatches) async {
+    List<SearchResult> results = await driver.search.references(element);
     _assertResults(results, expectedMatches);
     expect(results, hasLength(expectedMatches.length));
   }