Add cors to backend server (#524)

pynecone/app.py

@@ -3,6 +3,7 @@
 from typing import Any, Callable, Coroutine, Dict, List, Optional, Type, Union
 
 from fastapi import FastAPI
+from fastapi.middleware import cors
 from socketio import ASGIApp, AsyncNamespace, AsyncServer
 
 from pynecone import constants, utils
@@ -74,6 +75,8 @@ class App(Base):
 
         # Set up the API.
         self.api = FastAPI()
+        self.add_cors(config.cors_allowed_origins)
+        self.add_default_endpoints()
 
         # Set up CORS options.
         cors_allowed_origins = config.cors_allowed_origins
@@ -116,6 +119,26 @@ class App(Base):
         """
         return self.api
 
+    def add_default_endpoints(self):
+        """Add the default endpoints."""
+        # To test the server.
+        self.api.get(str(constants.Endpoint.PING))(ping)
+
+    def add_cors(self, allowed_origins: Optional[List[str]] = None):
+        """Add CORS middleware to the app.
+
+        Args:
+            allowed_origins: A list of allowed origins.
+        """
+        allowed_origins = allowed_origins or ["*"]
+        self.api.add_middleware(
+            cors.CORSMiddleware,
+            allow_origins=allowed_origins,
+            allow_credentials=True,
+            allow_methods=["*"],
+            allow_headers=["*"],
+        )
+
     def preprocess(self, state: State, event: Event) -> Optional[Delta]:
         """Preprocess the event.
 
@@ -392,6 +415,15 @@ async def process(
     return update
 
 
+async def ping() -> str:
+    """Test API endpoint.
+
+    Returns:
+        The response.
+    """
+    return "pong"
+
+
 class EventNamespace(AsyncNamespace):
     """The event namespace."""
 

pynecone/constants.py

@@ -159,6 +159,7 @@ class LogLevel(str, Enum):
 class Endpoint(Enum):
     """Endpoints for the pynecone backend API."""
 
+    PING = "ping"
     EVENT = "event"
 
     def __str__(self) -> str: