Allowing cross-origin requests in Yesod

Question

My application uses a bookmarklet, and I need to allow CORS for MyRouteR so my bookmarklet code can use this route for AJAX requests.

In my first draft

Answer 1

UPDATE: Someone else published some generic middleware for this: http://hackage.haskell.org/package/wai-cors.

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I am currently working on the same thing and haven't yet implemented a solution, however I imagine it can be done via a WAI Middleware similar to the sample code on the wiki page Allowing WOFF fonts to be accessed from other domains (CORS). This should allow you from writing the CORS code once without repeating yourself.

Sample code from the link above to add cross-origin access for WOFF fonts:

addCORStoWOFF :: W.Middleware
addCORStoWOFF app = fmap updateHeaders . app
  where
    updateHeaders (W.ResponseFile    status headers fp mpart) = W.ResponseFile    status (new headers) fp mpart
    updateHeaders (W.ResponseBuilder status headers builder)  = W.ResponseBuilder status (new headers) builder
    updateHeaders (W.ResponseSource  status headers src)      = W.ResponseSource  status (new headers) src
    new headers | woff      = cors : headers
                | otherwise =        headers
      where woff = lookup HT.hContentType headers == Just "application/font-woff"
            cors = ("Access-Control-Allow-Origin", "*")