add escape hatch for react version (#5225)

reflex/constants/installer.py

@@ -86,6 +86,18 @@ def _determine_nextjs_version() -> str:
     return default_version
 
 
+def _determine_react_version() -> str:
+    default_version = "19.1.0"
+    if (version := os.getenv("REACT_VERSION")) and version != default_version:
+        from reflex.utils import console
+
+        console.warn(
+            f"You have requested react@{version} but the supported version is {default_version}, abandon all hope ye who enter here."
+        )
+        return version
+    return default_version
+
+
 class PackageJson(SimpleNamespace):
     """Constants used to build the package.json file."""
 
@@ -99,6 +111,8 @@ class PackageJson(SimpleNamespace):
 
     PATH = "package.json"
 
+    _react_version = _determine_react_version()
+
     DEPENDENCIES = {
         "@emotion/react": "11.14.0",
         "axios": "1.9.0",
@@ -106,8 +120,8 @@ class PackageJson(SimpleNamespace):
         "next": _determine_nextjs_version(),
         "next-sitemap": "4.2.3",
         "next-themes": "0.4.6",
-        "react": "19.1.0",
-        "react-dom": "19.1.0",
+        "react": _react_version,
+        "react-dom": _react_version,
         "react-focus-lock": "2.13.6",
         "socket.io-client": "4.8.1",
         "universal-cookie": "7.2.2",
@@ -119,5 +133,5 @@ class PackageJson(SimpleNamespace):
     }
     OVERRIDES = {
         # This should always match the `react` version in DEPENDENCIES for recharts compatibility.
-        "react-is": "19.1.0"
+        "react-is": _react_version
     }