Validated Hamlet Textarea Form Field

Here is my custom textarea field that validates correct hamlet content

in the Form:
...
  (hamletHtmlResult, hamletHtmlView) <- mreq validatedHamletTextareaField
...

the field:

validatedHamletTextareaField :: Field (HandlerFor App) Textarea
validatedHamletTextareaField = checkM isValidHamlet textareaField
  where
    isValidHamlet :: Textarea -> Handler (Either AppMessage Textarea)
    isValidHamlet textarea@(Textarea text) = do
      eitherParsedTemplate <- tryParse text
      return $
        case eitherParsedTemplate of
          Left _ -> Left MsgGlobalInvalidHamlet
          Right _ -> Right $ Textarea text
      where
        tryParse :: Text -> Handler (Either SomeException HamletTemplate)
        tryParse text = try $ parseHamletTemplate defaultHamletSettings $ unpack text

Ways to stream yesod data to the client

model:

Rawdata
  bytes ByteString


way 1:

  addHeader "Content-Disposition" $
    T.concat ["attachment; filename=\"", filename, "\""]
  rawdata <- runDB $ get404 rawdataId                                                                                                                                         
  let bytes = rawdataBytes rawdata                                                                                                                                            
  sendResponse (TE.encodeUtf8 mimetype, toContent bytes)                                                                                                                      


way 2:

  let bytesSource = selectSource [RawdataId ==. rawdataId] []                                                                                                                 
  respondSourceDB (TE.encodeUtf8 mimetype) $ bytesSource $= awaitForever toBuilder'                                                                                           
  where                                                                                                                                                                       
    toBuilder' (Entity _ rawdata) = do                                                                                                                                        
      sendChunkBS $ rawdataBytes rawdata                                                                                                                                      
      sendFlush                                                                                                                                                               


way 3:

  let bytesSource = E.selectSource $ E.from $ \rd -> do
        E.where_ (rd E.^. RawdataId E.==. E.val rawdataId)
        return $ rd E.^. RawdataBytes
  respondSourceDB (TE.encodeUtf8 mimetype) $ bytesSource $= awaitForever toBuilder'
  where
    toBuilder' (E.Value bytes) = do
      sendChunkBS bytes
      sendFlush

nixos haskell yesod package with overrides

create a new file my-stack-project.nix:

let
  pkgs = import  {};
  pkg = pkgs.haskellPackages.callCabal2nix "my-stack-project" ./. {};
in
  pkgs.haskell.lib.overrideCabal pkg (_: {
    doHaddock = false;
    postInstall = ''
      cp -r ./static $out/bin
      cp -r ./config $out/bin
    '';
  })

Yesod embed json in html

getPersonListR :: Handler Html
getPersonListR = do
  urlRender <- getUrlRender
  personEnts <- runDB $ selectList [] [Asc PersonId]
  let jData = map (\(Entity personId person) ->
                      JPerson { jPersonPerson = person
                              , jPersonEditFormUrl = urlRender $ PersonEditFormR personId }
                  ) personEnts
  jsonData <- returnJson jData >>= return . toJsonText
  defaultLayout $ do
    toWidgetBody [julius|var data = #{rawJS jsonData}|]
    $(widgetFile "person_list")

data JPerson = JPerson
  { jPersonPerson :: Person
  , jPersonEditFormUrl :: Text
  }

haskell yesod curl POST request ... handling CSRF

get the cookie with token in it:

$ curl -c cookie.txt http://localhost:3000/

$ cat cookie.txt 
# Netscape HTTP Cookie File
# http://curl.haxx.se/docs/http-cookies.html
# This file was generated by libcurl! Edit at your own risk.

#HttpOnly_localhost FALSE / FALSE 1451524550 _SESSION gxV1yVNefLhiS7K3/ukfWWi5GXfD7wXfwJFYDXk3fz/HvyPqcSIcU7BBIKdOrj0jrpcU9DroL0+ioD3rr8cbvCSy+A+jPDpt/8kkiSPjYE86cGyTiueVo2cOGWcc8=
localhost FALSE / FALSE 0 XSRF-TOKEN seQLdve8GY


use token:

$ curl -v \
    --cookie cookie.txt \
    -c cookie.txt \
    -H "x-xsrf-token: seQLdve8GY" \
    -H "Accept: application/json" \
    -H "Content-Type: application/json" \
    -X POST \
    -d '{"foo":"bar", ...}' \
    http://localhost:3000/updateDruckprodukt

yesod persistent enum type

State.hs

{-# LANGUAGE TemplateHaskell #-}
module State where

import Database.Persist.TH
import Prelude

data State = New | Released
    deriving (Show, Read, Eq)
derivePersistField "State"

models

MyModel json
    state S.State
    createdAt UTCTime default=CURRENT_TIME

Model.hs

import qualified State as S

instance ToJSON S.State where
    toJSON S.New = String "New"
    toJSON S.Released = String "Released"

instance FromJSON S.State where
    parseJSON (String "New") = pure S.New
    parseJSON (String "Released") = pure S.Released

install yesod on debian wheezy

# apt-get install haskell-platform
# apt-get install yesod

$ yesod init
$ cd 
$ cabal install
$ yesod devel

install yesod on FreeBSD

This is for FreeBSD 10.0

http://www.yesodweb.com/page/quickstart

$ sudo pkg install hs-haskell-platform
$ cabal update

... now this says that we should upgrade with: cabal install cabal-install
... but do NOT do it, otherwise some packages will not find some header files

$ cabal install yesod-platform yesod-bin --max-backjumps=-1 --reorder-goals

... this takes long

$ ghc-pkg list | grep yesod
    yesod-1.2.5.2
    yesod-auth-1.3.0.4
    yesod-auth-hashdb-1.3.0.1
    yesod-core-1.2.14
    yesod-form-1.3.8.2
    yesod-persistent-1.2.2.3
    yesod-platform-1.2.10
    yesod-routes-1.2.0.6
    yesod-static-1.2.2.5
    yesod-test-1.2.1.2

If you happen to mess up the ghc/cabal packages, just

rm -rf ~/.cabal ~/.ghc/