[DAS] Fixes ignore_for_file fix when documentation comments in first line

Fixes: #61892
Change-Id: Ia4b21162f6c231c5fc456457de32a30612c1cfe9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/459320
Reviewed-by: Samuel Rawlins <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: FMorschel

pkg/analysis_server/test/src/services/correction/fix/ignore_diagnostic_test.dart

@@ -204,6 +204,23 @@ void f() {
     await assertHasFix('''
 // ignore_for_file: unused_local_variable
 
+void f() {
+  var a = 1;
+}
+''');
+  }
+
+  Future<void> test_docCommentsAtStart() async {
+    await resolveTestCode('''
+/// some comment
+void f() {
+  var a = 1;
+}
+''');
+    await assertHasFix('''
+// ignore_for_file: unused_local_variable
+
+/// some comment
 void f() {
   var a = 1;
 }

pkg/analysis_server_plugin/lib/src/correction/ignore_diagnostic.dart

@@ -4,6 +4,7 @@
 
 import 'package:analysis_server_plugin/edit/dart/correction_producer.dart';
 import 'package:analysis_server_plugin/edit/dart/dart_fix_kind_priority.dart';
+import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/diagnostic/diagnostic.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/analysis/analysis_options.dart';
@@ -174,6 +175,14 @@ class IgnoreDiagnosticInFile extends _DartIgnoreDiagnostic {
           continue;
         }
 
+        if (utils.findNode(lineStart) case var node?) {
+          var unitMember = node.thisOrAncestorOfType<CompilationUnitMember>();
+          var reference = unitMember?.documentationComment ?? node;
+          lineStart = reference.offset;
+          // Found code with possible doc-comment; insert before that.
+          break;
+        }
+
         // We found some code.
         break;
       }