Issue 25251. Fix for extracting string literal part with zero length.

pkg/analysis_server/test/edit/refactoring_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.edit.refactoring;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/edit/edit_domain.dart';
@@ skipping 296 matching lines @@
     },
         '''
 main() {
   var res = 1 + 2;
   print(res);
   print(res);
 }
 ''');
   }
 
+  solo_test_extractAll_string() {
+    addTestFile('''
+main() {
+  print("foo");
+}
+''');
+    return assertSuccessfulRefactoring(() {
+      return sendStringRequest('oo"', 'res', true);
+    },
+        '''
+main() {
+  var res = "foo";
+  print(res);
+}
+''');
+  }
+
   test_extractOne() {
     addTestFile('''
 main() {
   print(1 + 2);
   print(1 + 2); // marker
 }
 ''');
     return assertSuccessfulRefactoring(() {
       return sendStringSuffixRequest('1 + 2', '); // marker', 'res', false);
     },
@@ skipping 1589 matching lines @@
         .toRequest('0');
     return _assertErrorResponseNoIndex(request);
   }
 
   _assertErrorResponseNoIndex(Request request) async {
     Response response = await serverChannel.sendRequest(request);
     expect(response.error, isNotNull);
     expect(response.error.code, RequestErrorCode.NO_INDEX_GENERATED);
   }
 }