Improve import prefix search results UI.

pkg/analysis_server/test/search/element_references_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.search.element_references;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 279 matching lines @@
 }
 ''');
     return findElementReferences('mmm() {} // in B', false).then((_) {
       expect(searchElement.kind, ElementKind.METHOD);
       assertHasResult(SearchResultKind.INVOCATION, 'mmm(10)');
       assertHasResult(SearchResultKind.INVOCATION, 'mmm(20)');
       assertHasResult(SearchResultKind.INVOCATION, 'mmm(30)');
     });
   }
 
-  test_prefix() {
-    addTestFile('''
-import 'dart:async' as ppp;
-main() {
-  ppp.Future a;
-  ppp.Stream b;
-}
-''');
-    return findElementReferences("ppp;", false).then((_) {
-      expect(searchElement.kind, ElementKind.PREFIX);
-      expect(searchElement.name, 'ppp');
-      expect(searchElement.location.startLine, 1);
-      expect(results, hasLength(3));
-      assertHasResult(SearchResultKind.DECLARATION, 'ppp;');
-      assertHasResult(SearchResultKind.REFERENCE, 'ppp.Future');
-      assertHasResult(SearchResultKind.REFERENCE, 'ppp.Stream');
-    });
-  }
-
   test_label() {
     addTestFile('''
 main() {
 myLabel:
   for (int i = 0; i < 10; i++) {
     if (i == 2) {
       continue myLabel; // continue
     }
     break myLabel; // break
   }
@@ skipping 299 matching lines @@
   b.test(3);
 }
 ''');
     return findElementReferences('test(_) {} // of Derived', true).then((_) {
       assertHasRef(SearchResultKind.INVOCATION, 'test(1);', true);
       assertHasRef(SearchResultKind.INVOCATION, 'test(2);', false);
       assertHasRef(SearchResultKind.INVOCATION, 'test(3);', true);
     });
   }
 
+  test_prefix() {
+    addTestFile('''
+import 'dart:async' as ppp;
+main() {
+  ppp.Future a;
+  ppp.Stream b;
+}
+''');
+    return findElementReferences("ppp;", false).then((_) {
+      expect(searchElement.kind, ElementKind.PREFIX);
+      expect(searchElement.name, 'ppp');
+      expect(searchElement.location.startLine, 1);
+      expect(results, hasLength(3));
+      assertHasResult(SearchResultKind.DECLARATION, 'ppp;');
+      assertHasResult(SearchResultKind.REFERENCE, 'ppp.Future');
+      assertHasResult(SearchResultKind.REFERENCE, 'ppp.Stream');
+    });
+  }
+
+  test_prefix_null() {
+    addTestFile('''
+import 'dart:async';
+main() {
+  Future a;
+  Stream b;
+}
+''');
+    return findElementReferences("import ", false).then((_) {
+      expect(searchElement, isNull);
+    });
+  }
+
   test_topLevelVariable_explicit() {
     addTestFile('''
 var vvv = 1;
 main() {
   print(vvv);
   vvv += 3;
   vvv = 2;
   vvv();
 }
 ''');
@@ skipping 66 matching lines @@
 }
 ''');
     return findElementReferences('T> {', false).then((_) {
       expect(searchElement.kind, ElementKind.TYPE_PARAMETER);
       expect(results, hasLength(2));
       assertHasResult(SearchResultKind.REFERENCE, 'T f;');
       assertHasResult(SearchResultKind.REFERENCE, 'T m()');
     });
   }
 }