Don't remove ResultData(s) for incrementally updated results.

pkg/analyzer/test/src/context/context_test.dart

 // Copyright (c) 2014, 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 test.src.context.context_test;
 
 import 'dart:async';
 
 import 'package:analyzer/src/cancelable_future.dart';
 import 'package:analyzer/src/context/cache.dart';
@@ skipping 1563 matching lines @@
         addSource("/test.dart", "library lib; part 'test-part.dart';");
     Source partSource = addSource("/test-part.dart", "part of lib;");
     _analyzeAll_assertFinished();
     expect(context.getResolvedCompilationUnit2(libSource, libSource), isNotNull,
         reason: "library resolved 1");
     expect(
         context.getResolvedCompilationUnit2(partSource, libSource), isNotNull,
         reason: "part resolved 1");
     // update and analyze #1
     context.setContents(partSource, "part of lib; // 1");
-    expect(context.getResolvedCompilationUnit2(libSource, libSource), isNull,
-        reason: "library changed 2");
-    expect(context.getResolvedCompilationUnit2(partSource, libSource), isNull,
-        reason: "part changed 2");
-    _analyzeAll_assertFinished();
-    expect(context.getResolvedCompilationUnit2(libSource, libSource), isNotNull,
-        reason: "library resolved 2");
-    expect(
-        context.getResolvedCompilationUnit2(partSource, libSource), isNotNull,
-        reason: "part resolved 2");
+    if (AnalysisEngine.instance.limitInvalidationInTaskModel) {
+      expect(
+          context.getResolvedCompilationUnit2(libSource, libSource), isNotNull,
+          reason: "library changed 2");
+      expect(
+          context.getResolvedCompilationUnit2(partSource, libSource), isNotNull,
+          reason: "part changed 2");
+    } else {
+      expect(context.getResolvedCompilationUnit2(libSource, libSource), isNull,
+          reason: "library changed 2");
+      expect(context.getResolvedCompilationUnit2(partSource, libSource), isNull,
+          reason: "part changed 2");
+      _analyzeAll_assertFinished();
+      expect(
+          context.getResolvedCompilationUnit2(libSource, libSource), isNotNull,
+          reason: "library resolved 2");
+      expect(
+          context.getResolvedCompilationUnit2(partSource, libSource), isNotNull,
+          reason: "part resolved 2");
+    }
     // update and analyze #2
     context.setContents(partSource, "part of lib; // 12");
-    expect(context.getResolvedCompilationUnit2(libSource, libSource), isNull,
-        reason: "library changed 3");
-    expect(context.getResolvedCompilationUnit2(partSource, libSource), isNull,
-        reason: "part changed 3");
-    _analyzeAll_assertFinished();
-    expect(context.getResolvedCompilationUnit2(libSource, libSource), isNotNull,
-        reason: "library resolved 3");
-    expect(
-        context.getResolvedCompilationUnit2(partSource, libSource), isNotNull,
-        reason: "part resolved 3");
+    if (AnalysisEngine.instance.limitInvalidationInTaskModel) {
+      expect(
+          context.getResolvedCompilationUnit2(libSource, libSource), isNotNull,
+          reason: "library changed 3");
+      expect(
+          context.getResolvedCompilationUnit2(partSource, libSource), isNotNull,
+          reason: "part changed 3");
+    } else {
+      expect(context.getResolvedCompilationUnit2(libSource, libSource), isNull,
+          reason: "library changed 3");
+      expect(context.getResolvedCompilationUnit2(partSource, libSource), isNull,
+          reason: "part changed 3");
+      _analyzeAll_assertFinished();
+      expect(
+          context.getResolvedCompilationUnit2(libSource, libSource), isNotNull,
+          reason: "library resolved 3");
+      expect(
+          context.getResolvedCompilationUnit2(partSource, libSource), isNotNull,
+          reason: "part resolved 3");
+    }
   }
 
   void test_performAnalysisTask_importedLibraryAdd() {
     Source libASource =
         addSource("/libA.dart", "library libA; import 'libB.dart';");
     _analyzeAll_assertFinished();
     expect(
         context.getResolvedCompilationUnit2(libASource, libASource), isNotNull,
         reason: "libA resolved 1");
     expect(_hasAnalysisErrorWithErrorSeverity(context.getErrors(libASource)),
@@ skipping 446 matching lines @@
     AnalysisEngine.instance.limitInvalidationInTaskModel = true;
     super.setUp();
   }
 
   @override
   void tearDown() {
     AnalysisEngine.instance.limitInvalidationInTaskModel = false;
     super.tearDown();
   }
 
+  void test_noChange_thenChange() {
+    Source sourceA = addSource("/a.dart", r'''
+library lib_a;
+
+class A {
+  A();
+}
+class B {
+  B();
+}
+''');
+    Source sourceB = addSource("/b.dart", r'''
+library lib_b;
+import 'a.dart';
+main() {
+  new A();
+}
+''');
+    _performPendingAnalysisTasks();
+    expect(context.getErrors(sourceA).errors, hasLength(0));
+    expect(context.getErrors(sourceB).errors, hasLength(0));
+    var unitA = context.getResolvedCompilationUnit2(sourceA, sourceA);
+    var unitElementA = unitA.element;
+    var libraryElementA = unitElementA.library;
+    // Update a.dart, no declaration changes.
+    context.setContents(sourceA, r'''
+library lib_a;
+class A {
+  A();
+}
+class B {
+  B();
+}
+''');
+    _assertInvalid(sourceA, LIBRARY_ERRORS_READY);
+    _assertValid(sourceB, LIBRARY_ERRORS_READY);
+    // The a.dart's unit and element are updated incrementally.
+    // They are the same instances as initially.
+    // So, all the references from other units are still valid.
+    {
+      LibrarySpecificUnit target = new LibrarySpecificUnit(sourceA, sourceA);
+      expect(analysisCache.getValue(target, RESOLVED_UNIT1), same(unitA));
+      expect(unitA.element, same(unitElementA));
+      expect(unitElementA.library, same(libraryElementA));
+    }
+    // Analyze.
+    _performPendingAnalysisTasks();
+    expect(context.getErrors(sourceA).errors, hasLength(0));
+    expect(context.getErrors(sourceB).errors, hasLength(0));
+    // The a.dart's unit and element are the same.
+    {
+      LibrarySpecificUnit target = new LibrarySpecificUnit(sourceA, sourceA);
+      expect(analysisCache.getValue(target, RESOLVED_UNIT), same(unitA));
+      expect(unitA.element, same(unitElementA));
+      expect(unitElementA.library, same(libraryElementA));
+    }
+    // Update a.dart, rename A to A2, invalidates b.dart, so
+    // we know that the previous update did not damage dependencies.
+    context.setContents(sourceA, r'''
+library lib_a;
+class A {
+  A();
+  m() {}
+}
+class B {
+  B();
+}
+''');
+    _assertInvalid(sourceA, LIBRARY_ERRORS_READY);
+    _assertInvalid(sourceB, LIBRARY_ERRORS_READY);
+    // The a.dart's unit and element are the same.
+    {
+      LibrarySpecificUnit target = new LibrarySpecificUnit(sourceA, sourceA);
+      expect(analysisCache.getValue(target, RESOLVED_UNIT1), same(unitA));
+      expect(unitA.element, same(unitElementA));
+      expect(unitElementA.library, same(libraryElementA));
+    }
+    // Analyze.
+    _performPendingAnalysisTasks();
+    expect(context.getErrors(sourceA).errors, hasLength(0));
+    expect(context.getErrors(sourceB).errors, hasLength(0));
+  }
+
   void test_unusedName() {
     Source sourceA = addSource("/a.dart", r'''
 library lib_a;
 class A {}
 class B {}
 class C {}
 ''');
     Source sourceB = addSource("/b.dart", r'''
 library lib_b;
 import 'a.dart';
@@ skipping 131 matching lines @@
   }
 }
 
 class _AnalysisContextImplTest_test_applyChanges_removeContainer
     implements SourceContainer {
   Source libB;
   _AnalysisContextImplTest_test_applyChanges_removeContainer(this.libB);
   @override
   bool contains(Source source) => source == libB;
 }