Quick fix to ignore a specific error (#25915).

pkg/analysis_server/test/services/correction/fix_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.services.correction.fix;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/edit/fix/fix_core.dart';
 import 'package:analysis_server/plugin/edit/fix/fix_dart.dart';
@@ skipping 234 matching lines @@
         '''
 class Test {
   final int a;
   final int b;
   final int c;
   Test(this.a, this.b, [this.c]);
 }
 ''');
   }
 
+  test_addIgnoreWarning() async {
+    resolveTestUnit('''
+main() {
+  int x = ''; //invalid_assignment
+}
+''');
+    await assertHasFix(
+        DartFixKind.IGNORE_ERROR,
+        '''
+main() {
+  //ignore: invalid_assignment
+  int x = ''; //invalid_assignment
+}
+''');
+  }
+
   test_addMissingParameter_function_positional_hasNamed() async {
     resolveTestUnit('''
 test({int a}) {}
 main() {
   test(1);
 }
 ''');
     await assertNoFix(DartFixKind.ADD_MISSING_PARAMETER_POSITIONAL);
   }
 
@@ skipping 201 matching lines @@
     String message1 = "Expected to find ';'";
     String message2 = "Undefined name 'await'";
     expect(errors.map((e) => e.message), unorderedEquals([message1, message2]));
     for (AnalysisError error in errors) {
       if (error.message == message1) {
         List<Fix> fixes = await _computeFixes(error);
         expect(fixes, isEmpty);
       }
       if (error.message == message2) {
         List<Fix> fixes = await _computeFixes(error);
+        // remove ignore fix
+        fixes.removeWhere((Fix fix) => fix.kind == DartFixKind.IGNORE_ERROR);
         // has exactly one fix
         expect(fixes, hasLength(1));
         Fix fix = fixes[0];
         expect(fix.kind, DartFixKind.ADD_ASYNC);
         // apply to "file"
         List<SourceFileEdit> fileEdits = fix.change.edits;
         expect(fileEdits, hasLength(1));
         resultCode = SourceEdit.applySequence(testCode, fileEdits[0].edits);
         // verify
         expect(
@@ skipping 4748 matching lines @@
   @override
   void t() { }
 }
 ''');
   }
 
   void verifyResult(String expectedResult) {
     expect(resultCode, expectedResult);
   }
 }