[jsinterop] Add static check for JSName of static class members.

Static class members could technically be mapped to a name with dots,
but in the early days of JSInterop we thought this was not necessary
since it could also be modeled as a top-level member or by adding
additional classes and exposing the member as a simple name on a deeper
class.

This invariant was assumed by DDC (which crashed if this was not the
case) and ignored by dart2js.

This change adds a static check to ensure both compilers act
consistenlty.

Fixes https://github.com/dart-lang/sdk/issues/27926

Change-Id: I20e59fbb75f0378a58ca88dc3910e079b4eeb7a3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/247180
Reviewed-by: Riley Porter <rileyporter@google.com>
Commit-Queue: Riley Porter <rileyporter@google.com>

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

@@ -6939,6 +6939,16 @@ const MessageCode messageJsInteropExternalMemberNotJSAnnotated = const MessageCo
     correctionMessage:
         r"""Try removing the 'external' keyword or adding a JS interop annotation.""");
 
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> codeJsInteropInvalidStaticClassMemberName =
+    messageJsInteropInvalidStaticClassMemberName;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode messageJsInteropInvalidStaticClassMemberName = const MessageCode(
+    "JsInteropInvalidStaticClassMemberName",
+    problemMessage:
+        r"""JS interop static class members cannot have '.' in their JS name.""");
+
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Template<
     Message Function(

pkg/_js_interop_checks/lib/js_interop_checks.dart

@@ -14,6 +14,7 @@ import 'package:_fe_analyzer_shared/src/messages/codes.dart'
         messageJsInteropEnclosingClassJSAnnotationContext,
         messageJsInteropExternalExtensionMemberOnTypeInvalid,
         messageJsInteropExternalMemberNotJSAnnotated,
+        messageJsInteropInvalidStaticClassMemberName,
         messageJsInteropNamedParameters,
         messageJsInteropNonExternalConstructor,
         messageJsInteropNonExternalMember,
@@ -274,6 +275,18 @@ class JsInteropChecks extends RecursiveVisitor {
         // named parameters.
         _checkNoNamedParameters(procedure.function);
       }
+
+      // JS static methods cannot use a JS name with dots.
+      if (procedure.isStatic && procedure.enclosingClass != null) {
+        String name = getJSName(procedure);
+        if (name.contains('.')) {
+          _diagnosticsReporter.report(
+              messageJsInteropInvalidStaticClassMemberName,
+              procedure.fileOffset,
+              procedure.name.text.length,
+              procedure.fileUri);
+        }
+      }
     }
 
     if (_classHasStaticInteropAnnotation &&

pkg/dev_compiler/lib/src/kernel/compiler.dart

@@ -2645,16 +2645,9 @@ class ProgramCompiler extends ComputeOnceConstantVisitor<js_ast.Expression>
 
   js_ast.LiteralString _emitJSInteropStaticMemberName(NamedNode n) {
     if (!usesJSInterop(n)) return null;
-    var name = _annotationName(n, isPublicJSAnnotation);
-    if (name != null) {
-      if (name.contains('.')) {
-        throw UnsupportedError(
-            'static members do not support "." in their names. '
-            'See https://github.com/dart-lang/sdk/issues/27926');
-      }
-    } else {
-      name = getTopLevelName(n);
-    }
+    var name = _annotationName(n, isPublicJSAnnotation) ?? getTopLevelName(n);
+    assert(name != null && !name.contains('.'),
+        'JS interop checker rejects dotted names on static class members');
     return js.escapedString(name, "'");
   }
 

pkg/front_end/messages.status

@@ -562,6 +562,8 @@ JsInteropExternalExtensionMemberOnTypeInvalid/analyzerCode: Fail # Web compiler
 JsInteropExternalExtensionMemberOnTypeInvalid/example: Fail # Web compiler specific
 JsInteropExternalMemberNotJSAnnotated/analyzerCode: Fail # Web compiler specific
 JsInteropExternalMemberNotJSAnnotated/example: Fail # Web compiler specific
+JsInteropInvalidStaticClassMemberName/analyzerCode: Fail
+JsInteropInvalidStaticClassMemberName/example: Fail
 JsInteropJSClassExtendsDartClass/analyzerCode: Fail # Web compiler specific
 JsInteropJSClassExtendsDartClass/example: Fail # Web compiler specific
 JsInteropNamedParameters/analyzerCode: Fail # Web compiler specific

pkg/front_end/messages.yaml

@@ -5173,6 +5173,9 @@ JsInteropOperatorsNotSupported:
   problemMessage: "JS interop classes do not support operator methods."
   correctionMessage: "Try replacing this with a normal method."
 
+JsInteropInvalidStaticClassMemberName:
+  problemMessage: "JS interop static class members cannot have '.' in their JS name."
+
 JsInteropStaticInteropWithInstanceMembers:
   problemMessage: "JS interop class '#name' with `@staticInterop` annotation cannot declare instance members."
   correctionMessage: "Try moving the instance member to a static extension."

tests/lib/js/static_class_member_static_test.dart

@@ -0,0 +1,15 @@
+// Copyright (c) 2022, 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.
+
+import 'package:js/js.dart';
+
+@JS('a.Foo')
+class Foo {
+  @JS('c.d.plus')
+  external static plus1(arg);
+//                ^
+// [web] JS interop static class members cannot have '.' in their JS name.
+}
+
+main() {}