Key not present error in "the pragmatic haskeller" example from https://www.fpcomplete.com/user/adinapoli/the-pragmatic-haskeller/episode-1-json

error message

key "name" not present in { 
    "name": "Ciambellone Cake", 
    "ingredients": [ 
        { 
            "name": "Flour", 
            "quantity": 250, 
            "measure": "gr" 
        }, 
        { 
            "name": "Sugar", 
            "quantity": 250, 
            "measure": "gr" 
        }, 
        { 
            "name": "Sunflower Oil", 
            "quantity": 130, 
            "measure": "ml" 
        }, 
        { 
            "name": "Water", 
            "quantity": 130, 
            "measure": "ml" 
        }, 
        { 
            "name": "Egg", 
            "quantity": 3 
        }, 
        { 
            "name": "Yeast", 
            "quantity": 1 
        } 
    ], 
    "steps": [ 
        { 
            "step": "Mix everything", 
            "order": 1 
        }, 
        { 
            "step": "Cook in oven at 200 degrees", 
            "order": 2, 
            "duration": { 
                "duration": 30, 
                "measure": "minutes" 
            } 
        } 
    ] 
}

Main.hs

{-# LANGUAGE OverloadedStrings #-}
module Main where

import Data.Aeson
import Control.Applicative
import Control.Monad
import Data.Monoid
import qualified Data.ByteString.Lazy.Char8 as C8
import qualified Data.ByteString.Lazy as BL

-- Types
data Recipe = Recipe {
  recipeName :: String,
  ingredients :: [Ingredient],
  steps :: [Step]
  } deriving Show

type Measure = String

data Ingredient = Ingredient {
  ingredientName :: String,
  qantity :: Int,
  measure :: Maybe Measure
  } deriving Show
  
data Step = Step {
  stepName :: String,
  order :: Int,
  stepDuration :: Maybe Duration
  } deriving (Eq, Show) 
  
instance Ord Step where
  compare s1 s2 = compare (order s1) (order s2)

data Duration = Duration {
  duration :: Int,
  durationMeasure :: Measure
  } deriving (Eq, Show)

-- Parser
instance FromJSON Recipe where
  parseJSON (Object r) = Recipe <$>
                         r .: "name" <*>
                         r .: "ingredients" <*>
                         r .: "steps"
  parseJSON _ = mzero

instance ToJSON Recipe where
  toJSON (Recipe n i s) = object ["name" .= n, "ingredients" .= i, "steps" .= s]
  
instance FromJSON Ingredient where
  parseJSON (Object i) = Ingredient <$>
                         i .: "name" <*>
                         i .: "quantity" <*>
                         i .:? "measure"
  parseJSON _ = mzero

instance ToJSON Ingredient where
  toJSON (Ingredient n q m) = object ["name" .= n, "quantity" .= q, "measure" .= m]

instance FromJSON Step where
  parseJSON (Object s) = Step <$>
                         s .: "name" <*>
                         s .: "order" <*>
                         s .:? "duration"
  parseJSON _ = mzero

instance ToJSON Step where
  toJSON (Step n o d) = object ["name" .= n, "order" .= o, "duration" .= d]

instance FromJSON Duration where
  parseJSON (Object d) = Duration <$>
                         d .: "duration" <*>
                         d .: "measure"
  parseJSON _ = mzero

instance ToJSON Duration where
  toJSON (Duration d m) = object ["duration" .= d, "measure" .= m]

main :: IO ()
main = do
  content <- BL.readFile "recipe.json"
  case (eitherDecode' content :: Either String Recipe) of
           Right r -> print r
           Left e -> C8.putStrLn $ C8.pack e <> " in " <> content

recipe.json

{ 
    "name": "Ciambellone Cake", 
    "ingredients": [ 
        { 
            "name": "Flour", 
            "quantity": 250, 
            "measure": "gr" 
        }, 
        { 
            "name": "Sugar", 
            "quantity": 250, 
            "measure": "gr" 
        }, 
        { 
            "name": "Sunflower Oil", 
            "quantity": 130, 
            "measure": "ml" 
        }, 
        { 
            "name": "Water", 
            "quantity": 130, 
            "measure": "ml" 
        }, 
        { 
            "name": "Egg", 
            "quantity": 3 
        }, 
        { 
            "name": "Yeast", 
            "quantity": 1 
        } 
    ], 
    "steps": [ 
        { 
            "step": "Mix everything", 
            "order": 1 
        }, 
        { 
            "step": "Cook in oven at 200 degrees", 
            "order": 2, 
            "duration": { 
                "duration": 30, 
                "measure": "minutes" 
            } 
        } 
    ] 
}

changing "name" to "step" in Step instances fixes the problem