Add hook for listening to implicitly analyzed files

pkg/analyzer/test/generated/engine_test.dart

Index: pkg/analyzer/test/generated/engine_test.dart
diff --git a/pkg/analyzer/test/generated/engine_test.dart b/pkg/analyzer/test/generated/engine_test.dart
index feb01db1463b16b70463307227104e35c205d42a..cdb97acdb5dad98356b68e84094e212e7905b1dd 100644
--- a/pkg/analyzer/test/generated/engine_test.dart
+++ b/pkg/analyzer/test/generated/engine_test.dart
@@ -245,6 +245,21 @@ class AnalysisContextImplTest extends EngineTestCase {
     super.tearDown();
   }
 
+  Future test_analyzedSources_added() async {
+    AnalyzedSourcesListener listener = new AnalyzedSourcesListener();
+    _context.implicitAnalysisEvents.listen(listener.onData);
+    //
+    // Create a file that references an file that is not explicitly being
+    // analyzed and fully analyze it. Ensure that the listener is told about
+    // the implicitly analyzed file.
+    //
+    Source sourceA = _addSource('/a.dart', "library a; import 'b.dart';");
+    Source sourceB = _createSource('/b.dart', "library b;");
+    _context.computeErrors(sourceA);
+    await pumpEventQueue();
+    listener.expectAnalyzed(sourceB);
+  }
+
   Future test_applyChanges_add() {
     SourcesChangedListener listener = new SourcesChangedListener();
     _context.onSourcesChanged.listen(listener.onData);
@@ -2151,6 +2166,12 @@ library test2;''');
     _context.applyChanges(changeSet);
   }
 
+  Source _createSource(String fileName, String contents) {
+    Source source = new FileBasedSource(FileUtilities2.createFile(fileName));
+    _context.setContents(source, contents);
+    return source;
+  }
+
   /**
    * Search the given compilation unit for a class with the given name. Return the class with the
    * given name, or `null` if the class cannot be found.
@@ -2343,6 +2364,48 @@ class AnalysisTaskTest extends EngineTestCase {
   }
 }
 
+/**
+ * A listener used to gather the [ImplicitAnalysisEvent]s that are produced
+ * during analysis.
+ */
+class AnalyzedSourcesListener {
+  /**
+   * The events that have been gathered.
+   */
+  List<ImplicitAnalysisEvent> actualEvents = <ImplicitAnalysisEvent>[];
+
+  /**
+   * The sources that are being implicitly analyzed.
+   */
+  List<Source> analyzedSources = <Source>[];
+
+  /**
+   * Assert that the given source is currently being implicitly analyzed.
+   */
+  void expectAnalyzed(Source source) {
+    expect(analyzedSources, contains(source));
+  }
+
+  /**
+   * Assert that the given source is not currently being implicitly analyzed.
+   */
+  void expectNotAnalyzed(Source source) {
+    expect(analyzedSources, isNot(contains(source)));
+  }
+
+  /**
+   * Record that the given event was produced.
+   */
+  void onData(ImplicitAnalysisEvent event) {
+    actualEvents.add(event);
+    if (event.isAnalyzed) {
+      analyzedSources.add(event.source);
+    } else {
+      analyzedSources.remove(event.source);
+    }
+  }
+}
+
 class CompilationUnitMock extends TypedMock implements CompilationUnit {
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }
@@ -5468,6 +5531,11 @@ class TestAnalysisContext implements InternalAnalysisContext {
     return null;
   }
   @override
+  Stream<ImplicitAnalysisEvent> get implicitAnalysisEvents {
+    fail("Unexpected invocation of analyzedSources");
+    return null;
+  }
+  @override
   bool get isDisposed {
     fail("Unexpected invocation of isDisposed");
     return false;
@@ -5511,6 +5579,7 @@ class TestAnalysisContext implements InternalAnalysisContext {
     fail("Unexpected invocation of getPrioritySources");
     return null;
   }
+
   @override
   List<AnalysisTarget> get priorityTargets {
     fail("Unexpected invocation of visitCacheItems");
@@ -5528,7 +5597,6 @@ class TestAnalysisContext implements InternalAnalysisContext {
     fail("Unexpected invocation of getResolverVisitorFactory");
     return null;
   }
-
   @override
   SourceFactory get sourceFactory {
     fail("Unexpected invocation of getSourceFactory");
@@ -5790,6 +5858,7 @@ class TestAnalysisContext implements InternalAnalysisContext {
     fail("Unexpected invocation of parseHtmlUnit");
     return null;
   }
+
   @override
   AnalysisResult performAnalysisTask() {
     fail("Unexpected invocation of performAnalysisTask");
@@ -5832,11 +5901,11 @@ class TestAnalysisContext implements InternalAnalysisContext {
       int oldLength, int newLength) {
     fail("Unexpected invocation of setChangedContents");
   }
-
   @override
   void setContents(Source source, String contents) {
     fail("Unexpected invocation of setContents");
   }
+
   @override
   bool shouldErrorsBeAnalyzed(Source source, Object entry) {
     fail("Unexpected invocation of shouldErrorsBeAnalyzed");