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

See: https://github.com/dart-lang/sdk/issues/25915

BUG=
R=scheglov@google.com

Review URL: https://codereview.chromium.org/1764853002 .

pkg/analysis_server/lib/src/services/correction/fix.dart

@@ -158,6 +158,8 @@ class DartFixKind {
       'CREATE_MISSING_OVERRIDES', 49, "Create {0} missing override(s)");
   static const CREATE_NO_SUCH_METHOD = const FixKind(
       'CREATE_NO_SUCH_METHOD', 51, "Create 'noSuchMethod' method");
+  static const IGNORE_ERROR =
+      const FixKind('IGNORE_ERROR', 60, "Ignore error with code '{0}'");
   static const IMPORT_LIBRARY_PREFIX = const FixKind('IMPORT_LIBRARY_PREFIX',
       51, "Use imported library '{0}' with prefix '{1}'");
   static const IMPORT_LIBRARY_PROJECT =

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

@@ -143,6 +143,15 @@ class FixProcessor {
         new NodeLocator2(errorOffset, errorEnd - 1).searchWithin(unit);
     // analyze ErrorCode
     ErrorCode errorCode = error.errorCode;
+    // add ignore fix for ignorable errors.
+    // note that this fix needs to be added before fixes that side-effect
+    // the utils instance.
+    if (errorCode is StaticWarningCode ||
+        errorCode is StaticTypeWarningCode ||
+        errorCode is HintCode ||
+        errorCode is LintCode) {
+      _addFix_ignore(errorCode);
+    }
     if (errorCode == StaticWarningCode.UNDEFINED_CLASS_BOOLEAN) {
       _addFix_boolInsteadOfBoolean();
     }
@@ -1383,6 +1392,18 @@ class FixProcessor {
     }
   }
 
+  void _addFix_ignore(ErrorCode errorCode) {
+    int offset = node.offset;
+    int lineOffset = utils.getLineThis(offset);
+
+    exitPosition = new Position(file, lineOffset - 1);
+    String indent = utils.getLinePrefix(offset);
+    String errorCodeName = errorCode.name.toLowerCase();
+    String content = '$indent//ignore: $errorCodeName$eol';
+    _addReplaceEdit(rf.rangeStartLength(lineOffset, 0), content);
+    _addFix(DartFixKind.IGNORE_ERROR, [errorCodeName]);
+  }
+
   void _addFix_illegalAsyncReturnType() {
     // prepare the existing type
     TypeName typeName = node.getAncestor((n) => n is TypeName);

pkg/analysis_server/test/edit/fixes_test.dart

@@ -9,6 +9,7 @@ import 'dart:async';
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/domain_analysis.dart';
 import 'package:analysis_server/src/edit/edit_domain.dart';
+import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:plugin/manager.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart' hide ERROR;
@@ -37,6 +38,7 @@ class FixesTest extends AbstractAnalysisTest {
     addTestFile('''
 main() {
   Future<String> x = null;
+  print(x);
 }
 ''');
     await waitForTasksFinished();
@@ -46,9 +48,11 @@ main() {
     expect(error.severity, AnalysisErrorSeverity.WARNING);
     expect(error.type, AnalysisErrorType.STATIC_WARNING);
     List<SourceChange> fixes = errorFixes[0].fixes;
-    expect(fixes, hasLength(2));
+    expect(fixes, hasLength(3));
     expect(fixes[0].message, matches('Import library'));
     expect(fixes[1].message, matches('Create class'));
+    expect(
+        fixes[2].message, matches("Ignore error with code 'undefined_class'"));
   }
 
   test_hasFixes() async {

pkg/analysis_server/test/services/correction/fix_test.dart

@@ -252,6 +252,22 @@ class Test {
 ''');
   }
 
+  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}) {}
@@ -473,6 +489,8 @@ main() {
       }
       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];