[pkg:js] Language version @Native/@JS class conflict check

Bug: https://github.com/dart-lang/sdk/issues/44797

This check was previously introduced without a language version,
and therefore lead to a breaking change on SDK update. It's now
versioned for releases >= 2.13, allowing users to migrate easier.
It also adds a hint for the error, providing alternatives for
users whose code triggers this check.

Change-Id: I4f61066a917ddb18071508291cde00710802fc5d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/182920
Commit-Queue: Srujan Gaddam <srujzs@google.com>
Reviewed-by: Sigmund Cherem <sigmund@google.com>

pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart

@@ -6026,6 +6026,8 @@ const Template<
         Message Function(String name, String name2, String string3)>(
     messageTemplate:
         r"""JS interop class '#name' conflicts with natively supported class '#name2' in '#string3'.""",
+    tipTemplate:
+        r"""Try making the @JS class into an @anonymous class or use js_util on the JS object.""",
     withArguments: _withArgumentsJsInteropNativeClassInAnnotation);
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
@@ -6046,6 +6048,7 @@ Message _withArgumentsJsInteropNativeClassInAnnotation(
   return new Message(codeJsInteropNativeClassInAnnotation,
       message:
           """JS interop class '${name}' conflicts with natively supported class '${name2}' in '${string3}'.""",
+      tip: """Try making the @JS class into an @anonymous class or use js_util on the JS object.""",
       arguments: {'name': name, 'name2': name2, 'string3': string3});
 }
 

pkg/_js_interop_checks/lib/js_interop_checks.dart

@@ -62,9 +62,6 @@ class JsInteropChecks extends RecursiveVisitor<void> {
   ];
 
   bool _libraryIsGlobalNamespace = false;
-  // TODO(srujzs): This currently disables this check always. This check should
-  // instead only be disabled up until a given language version.
-  bool _disableJSNativeClassConflict = true;
 
   JsInteropChecks(
       this._coreTypes, this._diagnosticsReporter, this._nativeClasses);
@@ -118,7 +115,8 @@ class JsInteropChecks extends RecursiveVisitor<void> {
             cls.location.file);
       }
     }
-    if (!_disableJSNativeClassConflict &&
+    // Since this is a breaking check, it is language-versioned.
+    if (cls.enclosingLibrary.languageVersion >= Version(2, 13) &&
         _classHasJSAnnotation &&
         !_classHasAnonymousAnnotation &&
         _libraryIsGlobalNamespace) {

pkg/front_end/messages.yaml

@@ -4694,6 +4694,7 @@ JsInteropNamedParameters:
 
 JsInteropNativeClassInAnnotation:
   template: "JS interop class '#name' conflicts with natively supported class '#name2' in '#string3'."
+  tip: "Try making the @JS class into an @anonymous class or use js_util on the JS object."
 
 JsInteropNonExternalConstructor:
   template: "JS interop classes do not support non-external constructors."

pkg/front_end/test/spell_checking_list_messages.txt

@@ -36,6 +36,7 @@ futureor
 h
 https
 interop
+js_util
 libraries.json
 list.filled
 loadlibrary

tests/lib/js/native_as_js_classes_static_test/language_version_test.dart

@@ -0,0 +1,17 @@
+// Copyright (c) 2021, 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.
+
+// @dart=2.12
+
+// Test that static check does not occur before language version 2.13.
+
+@JS()
+library language_version_test;
+
+import 'package:js/js.dart';
+
+@JS()
+class HTMLDocument {}
+
+void main() {}