[analysis_server] Fix "Move to File" for top-level variables with references to their getters

There were two issues here:

1. Analyzer's `prefixesUsedInLibrary` search did not handle when an element was not found in the library (for example when looking for a top level variable that doesn't match because it's referenced through a getter)
2. The refactor not looking for prefixes for getters/setters when updating other files

Fixes #59968

Change-Id: Ic560e06c45091937611b247e7fee26b9854873fd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/406844
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: DanTup

pkg/analysis_server/lib/src/services/refactoring/move_top_level_to_file.dart

@@ -168,11 +168,23 @@ class MoveTopLevelToFile extends RefactoringProducer {
       var library = entry.key;
       var prefixes = <String>{};
       for (var element in entry.value) {
-        var prefixList = await searchEngine.searchPrefixesUsedInLibrary(
-          library,
-          element,
+        // Search for prefixes for the element.
+        prefixes.addAll(
+          await searchEngine.searchPrefixesUsedInLibrary(library, element),
         );
-        prefixes.addAll(prefixList);
+        // And also for the getter if this might be something like a top-level
+        // variable.
+        if (element case PropertyInducingElement2(:var getter2?)) {
+          prefixes.addAll(
+            await searchEngine.searchPrefixesUsedInLibrary(library, getter2),
+          );
+        }
+        // And setters.
+        if (element case PropertyInducingElement2(:var setter2?)) {
+          prefixes.addAll(
+            await searchEngine.searchPrefixesUsedInLibrary(library, setter2),
+          );
+        }
       }
       await builder.addDartFileEdit(library.firstFragment.source.fullName, (
         builder,

pkg/analysis_server/test/src/services/refactoring/move_top_level_to_file_test.dart

@@ -1820,6 +1820,53 @@ part of 'containing_library.dart';
     );
   }
 
+  /// https://github.com/dart-lang/sdk/issues/59968#issuecomment-2622191812
+  Future<void> test_single_topLevelVariable_withReferenceToGetter() async {
+    var originalSource = '''
+class A {}
+
+
+int variableT^oMove = 3;
+
+class B {}
+''';
+    var otherFilePath = '$projectFolderPath/lib/other.dart';
+    var otherFileContent = '''
+import "main.dart";
+
+void f() {
+  print(variableToMove);
+}
+''';
+
+    var declarationName = 'variableToMove';
+
+    var expected = '''
+>>>>>>>>>> lib/main.dart
+class A {}
+
+class B {}
+>>>>>>>>>> lib/other.dart
+import "package:test/variable_to_move.dart";
+
+import "main.dart";
+
+void f() {
+  print(variableToMove);
+}
+>>>>>>>>>> lib/variable_to_move.dart created
+int variableToMove = 3;
+''';
+
+    await _singleDeclaration(
+      originalSource: originalSource,
+      expected: expected,
+      declarationName: declarationName,
+      otherFilePath: otherFilePath,
+      otherFileContent: otherFileContent,
+    );
+  }
+
   Future<void> test_single_typedef() async {
     var originalSource = '''
 class A {}

pkg/analyzer/lib/src/dart/analysis/search.dart

@@ -357,8 +357,10 @@ class Search {
       if (index != null) {
         _IndexRequest request = _IndexRequest(index);
         int elementId = request.findElementId(element.asElement!);
-        var prefixList = index.elementImportPrefixes[elementId].split(',');
-        prefixes.addAll(prefixList);
+        if (elementId != -1) {
+          var prefixList = index.elementImportPrefixes[elementId].split(',');
+          prefixes.addAll(prefixList);
+        }
       }
     }
     return prefixes;