Add the guessApproot function (pinging @gregwebs)

yesod-auth/openid.hs

@@ -38,7 +38,7 @@ $nothing
 |]
 
 instance Yesod BID where
-    approot = ApprootStatic "http://localhost:3000"
+    approot = guessApproot
 
 instance YesodAuth BID where
     type AuthId BID = Text

yesod-core/ChangeLog.md

@@ -1,3 +1,7 @@
+## 1.4.16
+
+* Add `guessApproot`
+
 ## 1.4.15
 
 * mkYesod avoids using reify when it isn't necessary. This avoids needing to define the site type below the call to mkYesod.

yesod-core/Yesod/Core.hs

@@ -71,6 +71,8 @@ module Yesod.Core
     , MonadWidget (..)
     , getRouteToParent
     , defaultLayoutSub
+      -- * Approot
+    , guessApproot
       -- * Misc
     , yesodVersion
     , yesodRender

yesod-core/Yesod/Core/Class/Yesod.hs

@@ -56,6 +56,7 @@ import           Yesod.Core.Internal.Session
 import           Yesod.Core.Widget
 import Control.Monad.Trans.Class (lift)
 import Data.CaseInsensitive (CI)
+import qualified Network.Wai.Request
 
 -- | Define settings for a Yesod applications. All methods have intelligent
 -- defaults, and therefore no implementation is required.
@@ -826,3 +827,19 @@ fileLocationToString loc = (loc_package loc) ++ ':' : (loc_module loc) ++
   where
     line = show . fst . loc_start
     char = show . snd . loc_start
+
+-- | Guess the approot based on request headers. For more information, see
+-- "Network.Wai.Middleware.Approot"
+--
+-- In the case of headers being unavailable, it falls back to 'ApprootRelative'
+--
+-- Since 1.4.16
+guessApproot :: Approot site
+guessApproot = ApprootRequest $ \_master req ->
+    case W.requestHeaderHost req of
+        Nothing -> ""
+        Just host ->
+            (if Network.Wai.Request.appearsSecure req
+                then "https://"
+                else "http://")
+            `T.append` TE.decodeUtf8With TEE.lenientDecode host

yesod-core/yesod-core.cabal

@@ -1,5 +1,5 @@
 name:            yesod-core
-version:         1.4.15
+version:         1.4.16
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>
@@ -25,7 +25,7 @@ library
     build-depends:   base                  >= 4.3      && < 5
                    , time                  >= 1.1.4
                    , wai                   >= 3.0
-                   , wai-extra             >= 3.0.5
+                   , wai-extra             >= 3.0.7
                    , bytestring            >= 0.9.1.4
                    , text                  >= 0.7
                    , template-haskell