expose a 'hasFix' field on analyzer diagnostics (#3127)

* expose a 'hasFix' field on analyzer diagnostics

* fix test expectations

pkgs/dart_services/lib/src/analysis.dart

@@ -285,6 +285,7 @@ class AnalysisServerWrapper {
             ),
           );
         }).toList(),
+        hasFix: error.hasFix,
       );
 
       return issue;

pkgs/dart_services/test/analysis_test.dart

@@ -86,7 +86,8 @@ void defineTests() {
     test('Warn on deprecated web library imports', () async {
       final results = await analysisServer.analyze(deprecatedWebLibrary);
 
-      expect(results.issues, hasLength(1));
+      // Expect one or two deprecation messages.
+      expect(results.issues, anyOf(hasLength(1), hasLength(2)));
       final issue = results.issues.first;
       expect(issue.message, contains('Deprecated core web library'));
     });

pkgs/dartpad_shared/lib/model.dart

@@ -46,6 +46,11 @@ class AnalysisIssue {
   final String? url;
   final List<DiagnosticMessage>? contextMessages;
 
+  /// A hint to indicate to interested clients that this error has an associated
+  /// fix (or fixes). The absence of this field implies there are not known to
+  /// be fixes.
+  final bool? hasFix;
+
   AnalysisIssue({
     required this.kind,
     required this.message,
@@ -54,6 +59,7 @@ class AnalysisIssue {
     this.correction,
     this.url,
     this.contextMessages,
+    this.hasFix,
   });
 
   factory AnalysisIssue.fromJson(Map<String, Object?> json) =>