From 421014fdf5688cf3f943d3ac0d8a5970c25e3452 Mon Sep 17 00:00:00 2001
From: Dan Abramov <dan.abramov@gmail.com>
Date: Fri, 11 Dec 2020 22:45:18 +0000
Subject: [PATCH] [Flight] Use lazy reference for existing modules (#20445)

---
 packages/react-server/src/ReactFlightServer.js | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/packages/react-server/src/ReactFlightServer.js b/packages/react-server/src/ReactFlightServer.js
index 8a6ee64d4d8dc..d6717a0830760 100644
--- a/packages/react-server/src/ReactFlightServer.js
+++ b/packages/react-server/src/ReactFlightServer.js
@@ -435,6 +435,14 @@ export function resolveModelToJSON(
       const writtenModules = request.writtenModules;
       const existingId = writtenModules.get(moduleKey);
       if (existingId !== undefined) {
+        if (parent[0] === REACT_ELEMENT_TYPE && key === '1') {
+          // If we're encoding the "type" of an element, we can refer
+          // to that by a lazy reference instead of directly since React
+          // knows how to deal with lazy values. This lets us suspend
+          // on this component rather than its parent until the code has
+          // loaded.
+          return serializeByRefID(existingId);
+        }
         return serializeByValueID(existingId);
       }
       try {