Make autoreload work on codespaces (#1167)

shiny/_autoreload.py

@@ -224,6 +224,11 @@ async def process_request(
     ) -> Optional[tuple[http.HTTPStatus, websockets.datastructures.HeadersLike, bytes]]:
         # If there's no Upgrade header, it's not a WebSocket request.
         if request_headers.get("Upgrade") is None:
+            # For some unknown reason, this fixes a tendency on GitHub Codespaces to
+            # correctly proxy through this request, but give a 404 when the redirect is
+            # followed and app_url is requested. With the sleep, both requests tend to
+            # succeed reliably.
+            await asyncio.sleep(1)
             return (http.HTTPStatus.MOVED_PERMANENTLY, [("Location", app_url)], b"")
 
     async with websockets.serve(

shiny/_hostenv.py

@@ -7,24 +7,34 @@
 from ipaddress import ip_address
 from subprocess import run
 from typing import Pattern
-from urllib.parse import urlparse
+from urllib.parse import ParseResult, urlparse
 
 
 def is_workbench() -> bool:
     return bool(os.getenv("RS_SERVER_URL") and os.getenv("RS_SESSION_URL"))
 
 
+def is_codespaces() -> bool:
+    # See https://docs.github.com/en/codespaces/developing-in-a-codespace/default-environment-variables-for-your-codespace
+    return bool(
+        os.getenv("CODESPACES")
+        and os.getenv("CODESPACE_NAME")
+        and os.getenv("GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN")
+    )
+
+
 def is_proxy_env() -> bool:
-    return is_workbench()
+    return is_workbench() or is_codespaces()
 
 
 port_cache: dict[int, str] = {}
 
 
 def get_proxy_url(url: str) -> str:
-    if not is_workbench():
+    if not is_proxy_env():
         return url
 
+    # Regardless of proxying strategy, we don't want to proxy URLs that are not loopback
     parts = urlparse(url)
     is_loopback = parts.hostname == "localhost"
     if not is_loopback:
@@ -35,6 +45,45 @@ def get_proxy_url(url: str) -> str:
     if not is_loopback:
         return url
 
+    # Regardless of proxying strategy, we need to know the port, whether explicit or
+    # implicit (from the scheme)
+    if parts.port is not None:
+        if parts.port == 0:
+            # Not sure if this is even legal but we're definitely not going to succeed
+            # in proxying it
+            return url
+        port = parts.port
+    elif parts.scheme.lower() in ["ws", "http"]:
+        port = 80
+    elif parts.scheme.lower() in ["wss", "https"]:
+        port = 443
+    else:
+        # No idea what kind of URL this is
+        return url
+
+    if is_workbench():
+        return _get_proxy_url_workbench(parts, port) or url
+    if is_codespaces():
+        return _get_proxy_url_codespaces(parts, port) or url
+    return url
+
+
+def _get_proxy_url_codespaces(parts: ParseResult, port: int) -> str | None:
+    # See https://docs.github.com/en/codespaces/developing-in-a-codespace/default-environment-variables-for-your-codespace
+    codespace_name = os.getenv("CODESPACE_NAME")
+    port_forwarding_domain = os.getenv("GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN")
+    netloc = f"{codespace_name}-{port}.{port_forwarding_domain}"
+    if parts.scheme.lower() in ["ws", "wss"]:
+        scheme = "wss"
+    elif parts.scheme.lower() in ["http", "https"]:
+        scheme = "https"
+    else:
+        return None
+
+    return parts._replace(scheme=scheme, netloc=netloc).geturl()
+
+
+def _get_proxy_url_workbench(parts: ParseResult, port: int) -> str | None:
     path = parts.path or "/"
 
     server_url = os.getenv("RS_SERVER_URL", "")
@@ -45,18 +94,6 @@ def get_proxy_url(url: str) -> str:
     server_url = re.sub("/$", "", server_url)
     session_url = re.sub("^/", "", session_url)
 
-    port = (
-        parts.port
-        if parts.port
-        else (
-            80
-            if parts.scheme in ["ws", "http"]
-            else 443 if parts.scheme in ["wss", "https"] else 0
-        )
-    )
-    if port == 0:
-        return url
-
     if port in port_cache:
         ptoken = port_cache[port]
     else:
@@ -67,9 +104,9 @@ def get_proxy_url(url: str) -> str:
                 encoding="ascii",
             )
         except FileNotFoundError:
-            return url
+            return None
         if res.returncode != 0:
-            return url
+            return None
         ptoken = res.stdout
         port_cache[port] = ptoken