Compute explicit imports

pkg/analyzer/lib/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.task.dart;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/utilities_general.dart';
 import 'package:analyzer/task/model.dart';
 
 /**
  * The analysis errors associated with a target.
  *
  * The value combines errors represented by multiple other results.
  */
 // TODO(brianwilkerson) If we want to associate errors with targets smaller than
 // a file, we will need other contribution points to collect them. In which case
 // we might want to rename this and/or document that it applies to files.
 final CompositeResultDescriptor<List<AnalysisError>> DART_ERRORS =
     new CompositeResultDescriptor<List<AnalysisError>>('DART_ERRORS');
 
 /**
+ * The sources of the libraries that are explicitly imported into a library.
+ *
+ * The list will be empty if there are no explicit imports, but will not be
+ * `null`.
+ *
+ * The result is only available for targets representing a Dart library.
+ */
+final ListResultDescriptor<Source> EXPLICITLY_IMPORTED_LIBRARIES =
+    new ListResultDescriptor<Source>('EXPLICITLY_IMPORTED_LIBRARIES', Source.EMPTY_ARRAY);
+
+/**
  * The sources of the libraries that are exported from a library.
  *
  * The list will be empty if there are no exported libraries, but will not be
  * `null`.
  *
  * The result is only available for targets representing a Dart library.
  */
 final ListResultDescriptor<Source> EXPORTED_LIBRARIES =
     new ListResultDescriptor<Source>('EXPORTED_LIBRARIES', Source.EMPTY_ARRAY);
 
 /**
- * The sources of the libraries that are imported into a library.
+ * The sources of the libraries that are implicitly or explicitly imported into
+ * a library.
  *
- * Not `null`.
- * The default value is empty.
- * When computed, this list will always contain at least `dart:core` source.
+ * The list will minimally contain the source for `dart:core` because it is
+ * implicitly imported into every library, and therefore will never be `null`.
  *
  * The result is only available for targets representing a Dart library.
  */
 final ListResultDescriptor<Source> IMPORTED_LIBRARIES =
     new ListResultDescriptor<Source>('IMPORTED_LIBRARIES', Source.EMPTY_ARRAY);
 
 /**
  * The sources of the parts that are included in a library.
  *
  * The list will be empty if there are no parts, but will not be `null`. The
@@ skipping 105 matching lines @@
   @override
   bool operator ==(other) {
     return other is LibrarySpecificUnit &&
         other.library == library &&
         other.unit == unit;
   }
 
   @override
   String toString() => '$unit in $library';
 }