yesod devel does not have a hard-coded port

yesod/Scaffold/Devel.hs

@@ -83,7 +83,7 @@ devel cabalCmd = do
                 , concat
                     [ "import \""
                     , pi'
-                    , "\" Handler (withDevelApp)"
+                    , "\" Handler (withDevelAppPort)"
                     ]
                 , "import Data.Dynamic (fromDynamic)"
                 , "import Network.Wai.Handler.Warp (run)"
@@ -96,7 +96,8 @@ devel cabalCmd = do
                 , "main :: IO ()"
                 , "main = do"
                 , "    putStrLn \"Starting app\""
-                , "    forkIO $ (fromJust $ fromDynamic withDevelApp) $ run 3000"
+                , "    wdap <- return $ fromJust $ fromDynamic withDevelAppPort"
+                , "    forkIO $ wdap $ \\(port, app) -> run port app"
                 , "    loop"
                 , ""
                 , "loop :: IO ()"

yesod/scaffold/Handler.hs.cg

@@ -5,7 +5,7 @@
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 module Handler
     ( with~sitearg~
-    , withDevelApp
+    , withDevelAppPort
     ) where
 
 import ~sitearg~
@@ -62,15 +62,15 @@ with~sitearg~ conf logger f = do
   where
     s = static Settings.staticDir
 
-with~sitearg~LoadConfig :: Settings.AppEnvironment -> (Application -> IO a) -> IO ()
-with~sitearg~LoadConfig env f = do
-  conf <- Settings.loadConfig env
-  logger <- makeLogger
-  with~sitearg~ conf logger f
-  flushLogger logger
-
 -- for yesod devel
-withDevelApp :: Dynamic
-withDevelApp = do
-  toDyn ((with~sitearg~LoadConfig Settings.Development):: (Application -> IO ()) -> IO ())
-
+withDevelAppPort :: Dynamic
+withDevelAppPort =
+    toDyn go
+  where
+    go :: ((Int, Application) -> IO ()) -> IO ()
+    go f = do
+        conf <- Settings.loadConfig Settings.Development
+        let port = appPort conf
+        logger <- makeLogger
+        with~sitearg~ conf logger $ \app -> f (port, app)
+        flushLogger logger