From 5853b3c91019972da76960cebe77566096b007dd Mon Sep 17 00:00:00 2001
From: Josh Story <story@hey.com>
Date: Thu, 12 Oct 2023 15:02:26 -0700
Subject: [PATCH] [Fizz] Fix children rendering in custom elements with
 `enableCustomElementPropertySupport` (#27511)

The `enableCustomElementPropertySupport` flag changes React's handling
of custom elements in a way that is more useful that just treating every
prop as an attribute. However when server rendering we have no choice
but to serialize props as attributes. When this flag is on and React
supports more prop types on the client like functions and objects the
server implementation needs to be a bit more naunced in how it renders
these components. With this flag on `false`, function, and object props
are omitted entirely and `true` is normalized to `""`. There was a bug
however in the implementation which caused children more complex than a
single string to be omitted because it matched the object type filter.
This change reorganizes the code a bit to put these filters in the
default prop handline case, leaving children, style, and innerHTML to be
handled via normal logic.

fixes: https://github.com/facebook/react/issues/27286
---
 .../src/server/ReactFizzConfigDOM.js          | 41 +++++++++----------
 .../src/__tests__/ReactDOMFizzServer-test.js  | 26 ++++++++++++
 2 files changed, 45 insertions(+), 22 deletions(-)

diff --git a/packages/react-dom-bindings/src/server/ReactFizzConfigDOM.js b/packages/react-dom-bindings/src/server/ReactFizzConfigDOM.js
index 9c82cb6579231..99cb6db2a12b6 100644
--- a/packages/react-dom-bindings/src/server/ReactFizzConfigDOM.js
+++ b/packages/react-dom-bindings/src/server/ReactFizzConfigDOM.js
@@ -3134,32 +3134,13 @@ function pushStartCustomElement(
 
   let children = null;
   let innerHTML = null;
-  for (let propKey in props) {
+  for (const propKey in props) {
     if (hasOwnProperty.call(props, propKey)) {
       let propValue = props[propKey];
       if (propValue == null) {
         continue;
       }
-      if (
-        enableCustomElementPropertySupport &&
-        (typeof propValue === 'function' || typeof propValue === 'object')
-      ) {
-        // It is normal to render functions and objects on custom elements when
-        // client rendering, but when server rendering the output isn't useful,
-        // so skip it.
-        continue;
-      }
-      if (enableCustomElementPropertySupport && propValue === false) {
-        continue;
-      }
-      if (enableCustomElementPropertySupport && propValue === true) {
-        propValue = '';
-      }
-      if (enableCustomElementPropertySupport && propKey === 'className') {
-        // className gets rendered as class on the client, so it should be
-        // rendered as class on the server.
-        propKey = 'class';
-      }
+      let attributeName = propKey;
       switch (propKey) {
         case 'children':
           children = propValue;
@@ -3174,15 +3155,31 @@ function pushStartCustomElement(
         case 'suppressHydrationWarning':
           // Ignored. These are built-in to React on the client.
           break;
+        case 'className':
+          if (enableCustomElementPropertySupport) {
+            // className gets rendered as class on the client, so it should be
+            // rendered as class on the server.
+            attributeName = 'class';
+          }
+        // intentional fallthrough
         default:
           if (
             isAttributeNameSafe(propKey) &&
             typeof propValue !== 'function' &&
             typeof propValue !== 'symbol'
           ) {
+            if (enableCustomElementPropertySupport) {
+              if (propValue === false) {
+                continue;
+              } else if (propValue === true) {
+                propValue = '';
+              } else if (typeof propValue === 'object') {
+                continue;
+              }
+            }
             target.push(
               attributeSeparator,
-              stringToChunk(propKey),
+              stringToChunk(attributeName),
               attributeAssign,
               stringToChunk(escapeTextForBrowser(propValue)),
               attributeEnd,
diff --git a/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js b/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js
index a873a257528c5..5d9c8bcaeccc4 100644
--- a/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js
+++ b/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js
@@ -3624,6 +3624,32 @@ describe('ReactDOMFizzServer', () => {
     );
   });
 
+  // bugfix: https://github.com/facebook/react/issues/27286 affecting enableCustomElementPropertySupport flag
+  it('can render custom elements with children on ther server', async () => {
+    await act(() => {
+      renderToPipeableStream(
+        <html>
+          <body>
+            <my-element>
+              <div>foo</div>
+            </my-element>
+          </body>
+        </html>,
+      ).pipe(writable);
+    });
+
+    expect(getVisibleChildren(document)).toEqual(
+      <html>
+        <head />
+        <body>
+          <my-element>
+            <div>foo</div>
+          </my-element>
+        </body>
+      </html>,
+    );
+  });
+
   describe('error escaping', () => {
     it('escapes error hash, message, and component stack values in directly flushed errors (html escaping)', async () => {
       window.__outlet = {};