[web-devel] Re: Runtime Hamlet template parsing/rendering

[Simon Michael]

On 8/5/10 12:57 AM, Michael Snoyman wrote:
 > Thanks for the input everyone. I've just pushed the new Hamlet runtime code to github[1]. Instead of using data-object,
 > I've created a new datatype: HamletData[2]. Runtime templates support *almost* the entirety of valid Hamlet documents;

Excellent! With the following kludgery I was able to change hamlet files and see the effect immediately. A boon for 
development. Useful parse errors in the browser too. It's not all smooth of course. Including other hamlets and 
integrating RT and non-RT hamlets seems a lot of work.

...
import Yesod hiding (defaultHamletSettings)
import Control.Failure
import Text.Hamlet.Parse (defaultHamletSettings)
import Text.Hamlet.RT

stringToHamletRT :: Failure HamletException m => String -> m HamletRT
stringToHamletRT s = parseHamletRT defaultHamletSettings s

hamletRTToHtml :: Failure HamletException m => HamletData HledgerWebAppRoute -> HamletRT -> m (Html ())
hamletRTToHtml d h = renderHamletRT h d show

instance Failure HamletException (Handler HledgerWebApp)
     where failure = error . show

getAddformRT :: Handler HledgerWebApp RepHtml
getAddformRT = do
   ...
   dir <- appWebdir `fmap` getYesod
   addform <- liftIO $ readFile $ dir </> "addform.hamlet"
   -- addform uses the transactionfields template
   -- tfieldstmpl <- liftIO $ readFile $ dir </> "addformtransactionfields.hamlet"
   -- tfields1 <- stringToHamletRT tfieldstmpl >>= hamletRTToHtml
   --            (HDMap [("label", HDHtml $ string "To account")
   --                   ,("accthelp", HDHtml $ string "eg: expenses:food")
   --                   ,("amtfield", HDHtml $ preEscapedString $ printf "")
   --                   ...urgh
   -- tfields1 <- hamletToHamletRT $ transactionfields 1
   -- tfields2 <- hamletToHamletRT $ transactionfields 2
   -- ...urgh
   tfields1 <- stringToHamletRT ""
   tfields2 <-  stringToHamletRT ""
   h <- stringToHamletRT addform >>= hamletRTToHtml
       (HDMap [("date", HDHtml $ string "today")
              ,("desc", HDHtml $ string "")
              ,("datehelp", HDHtml $ string "eg: 7/20, 2010/1/1")
              ,("deschelp", HDHtml $ string "eg: supermarket (optional)")
              ,("transactionfields1", HDTemplate tfields1)
              ,("transactionfields2", HDTemplate tfields2)
              ])
   hamletToRepHtml $ pageLayout td [$hamlet|$h$|]