Issue 26044. Cache and use LibraryElementImpl.exportNamespace.

pkg/analyzer/lib/src/task/dart.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer.src.task.dart;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 2213 matching lines @@
         changedNames.contains(name) ||
         removedNames.contains(name);
   }
 
   bool nameChanged(String name) {
     return changedNames.add(name);
   }
 
   @override
   DeltaResult validate(InternalAnalysisContext context, AnalysisTarget target,
-      ResultDescriptor descriptor) {
+      ResultDescriptor descriptor, CacheState state, Object value) {
     if (hasDirectiveChange) {
       return DeltaResult.INVALIDATE;
     }
     // Prepare target source.
     Source targetSource = null;
     if (target is Source) {
       targetSource = target;
     }
     if (target is LibrarySpecificUnit) {
       targetSource = target.library;
     }
     if (target is Element) {
       targetSource = target.source;
     }
     // Keep results that are updated incrementally.
     // If we want to analyze only some references to the source being changed,
     // we need to keep the same instances of CompilationUnitElement and
     // LibraryElement.
     if (targetSource == source) {
       if (ParseDartTask.DESCRIPTOR.results.contains(descriptor)) {
         return DeltaResult.KEEP_CONTINUE;
       }
       if (BuildCompilationUnitElementTask.DESCRIPTOR.results
           .contains(descriptor)) {
         return DeltaResult.KEEP_CONTINUE;
       }
       if (BuildLibraryElementTask.DESCRIPTOR.results.contains(descriptor)) {
+        // Invalidate cached results.
+        if (value is LibraryElementImpl) {
+          value.exportNamespace = null;
+        }
         return DeltaResult.KEEP_CONTINUE;
       }
       return DeltaResult.INVALIDATE;
     }
     // Use the target library dependency information to decide whether
     // the delta affects the library.
     if (targetSource != null) {
       List<Source> librarySources =
           context.getLibrariesContaining(targetSource);
       for (Source librarySource in librarySources) {
@@ skipping 3078 matching lines @@
 
   @override
   bool moveNext() {
     if (_newSources.isEmpty) {
       return false;
     }
     currentTarget = _newSources.removeLast();
     return true;
   }
 }