Fix SSR @component functions rendering under CSR components

src/js/packages/@reactpy/client/src/vdom.tsx

@@ -93,7 +93,7 @@ function createImportSourceElement(props: {
       }
     }
   } else {
-    type = props.model.tagName;
+    type = props.model.tagName === "" ? Fragment : props.model.tagName;
   }
   return props.binding.create(
     type,

tests/test_reactjs/js_fixtures/nest-custom-under-web.js

@@ -0,0 +1,14 @@
+import React from "https://esm.sh/react@19.0"
+import ReactDOM from "https://esm.sh/react-dom@19.0/client"
+import {Container} from "https://esm.sh/react-bootstrap@2.10.10/?deps=react@19.0,react-dom@19.0,react-is@19.0&exports=Container";
+export {Container};
+
+export function bind(node, config) {
+  const root = ReactDOM.createRoot(node);
+  return {
+    create: (type, props, children) => 
+      React.createElement(type, props, children),
+    render: (element) => root.render(element, node),
+    unmount: () => root.unmount()
+  };
+}

tests/test_web/js_fixtures/nest-custom-under-web.js

@@ -0,0 +1,14 @@
+import React from "https://esm.sh/react@19.0"
+import ReactDOM from "https://esm.sh/react-dom@19.0/client"
+import {Container} from "https://esm.sh/react-bootstrap@2.10.10/?deps=react@19.0,react-dom@19.0,react-is@19.0&exports=Container";
+export {Container};
+
+export function bind(node, config) {
+  const root = ReactDOM.createRoot(node);
+  return {
+    create: (type, props, children) => 
+      React.createElement(type, props, children),
+    render: (element) => root.render(element, node),
+    unmount: () => root.unmount()
+  };
+}

tests/test_web/test_module.py

@@ -563,3 +563,32 @@ async def test_module_without_bind(display: DisplayFixture):
         "#my-generic-component", state="attached"
     )
     assert await element.inner_text() == "Hello World"
+
+async def test_nest_custom_component_under_web_component(display: DisplayFixture):
+    """
+    Fix https://github.com/reactive-python/reactpy/discussions/1323
+
+    Custom components (i.e those wrapped in the component decorator) were not able to
+    be nested under web components.
+
+    """
+    module = reactpy.reactjs.file_to_module(
+        "nest-custom-under-web", JS_FIXTURES_DIR / "nest-custom-under-web.js"
+    )
+    Container = reactpy.reactjs.module_to_vdom(module, "Container")
+
+    @reactpy.component
+    def CustomComponent():
+        return reactpy.html.div(
+            reactpy.html.h1({"id": "my-header"}, "Header 1")
+        )
+    await display.show(
+        lambda: Container(
+            CustomComponent()
+        )
+    )
+
+    element = await display.page.wait_for_selector(
+        "#my-header", state="attached"
+    )
+    assert await element.inner_text() == "Header 1"