Add warning if is is set and tries to update

sebmarkbage · sebmarkbage · commit 0bd9a679c02e · 2023-04-10T18:29:59.000-04:00
diff --git a/packages/react-dom-bindings/src/client/ReactDOMComponent.js b/packages/react-dom-bindings/src/client/ReactDOMComponent.js
@@ -657,6 +657,14 @@ function setProp(
       );
       break;
     // Properties that should not be allowed on custom elements.
+    case 'is': {
+      if (__DEV__ && prevValue != null) {
+        console.error(
+          'Cannot update the "is" prop after it has been initialized.',
+        );
+      }
+      break;
+    }
     case 'innerText':
     case 'textContent':
       if (enableCustomElementPropertySupport) {
