Verify that every type used with JSON content type in a servant API has compatible ToJSON and ToSchema instances using validateToJSON.

NOTE: validateEveryToJSON does not perform string pattern validation. See validateEveryToJSONWithPatternChecker.

validateEveryToJSON will produce one prop specification for every type in the API. Each type only gets one test, even if it occurs multiple times in the API.

>>> data User = User { name :: String, age :: Maybe Int } deriving (Show, Generic, Typeable)
>>> newtype UserId = UserId String deriving (Show, Generic, Typeable, ToJSON, Arbitrary)
>>> instance ToJSON User
>>> instance ToSchema User
>>> instance ToSchema UserId
>>> instance Arbitrary User where arbitrary = User <$> arbitrary <*> arbitrary
>>> type UserAPI = (Capture "user_id" UserId :> Get '[JSON] User) :<|> (ReqBody '[JSON] User :> Post '[JSON] UserId)

>>> hspec $ context "ToJSON matches ToSchema" $ validateEveryToJSON (Proxy :: Proxy UserAPI)

ToJSON matches ToSchema
  User
...
  UserId
...
Finished in ... seconds
2 examples, 0 failures

For the test to compile all body types should have the following instances:

• ToJSON and ToSchema are used to perform the validation;
• Typeable is used to name the test for each type;
• Show is used to display value for which ToJSON does not satisfy ToSchema.
• Arbitrary is used to arbitrarily generate values.

If any of the instances is missing, you'll get a descriptive type error:

>>> data Contact = Contact { fullname :: String, phone :: Integer } deriving (Show, Generic)
>>> instance ToJSON Contact
>>> instance ToSchema Contact
>>> type ContactAPI = Get '[JSON] Contact
>>> hspec $ validateEveryToJSON (Proxy :: Proxy ContactAPI)
...
...No instance for (Arbitrary Contact)
...  arising from a use of ‘validateEveryToJSON’
...

Verify that every type used with JSON content type in a servant API has compatible ToJSON and ToSchema instances using validateToJSONWithPatternChecker.

For validation without patterns see validateEveryToJSON.

Construct property tests for each type in a list. The name for each property is the name of the corresponding type.

>>> :{
 hspec $
   context "read . show == id" $
     props
       (Proxy :: Proxy [Eq, Show, Read])
       (\x -> read (show x) === x)
       (Proxy :: Proxy [Bool, Int, String])
:}

read . show == id
  Bool
...
  Int
...
  [Char]
...
Finished in ... seconds
3 examples, 0 failures

Pretty print validation errors together with actual JSON and OpenApi Schema (using encodePretty).

>>> import Data.Aeson
>>> import Data.Foldable (traverse_)
>>> data Person = Person { name :: String, phone :: Integer } deriving (Generic)
>>> instance ToJSON Person where toJSON p = object [ "name" .= name p ]
>>> instance ToSchema Person
>>> let person = Person { name = "John", phone = 123456 }
>>> traverse_ putStrLn $ prettyValidateWith validateToJSON person
Validation against the schema fails:
  * property "phone" is required, but not found in "{\"name\":\"John\"}"

JSON value:
{
    "name": "John"
}

OpenApi Schema:
{
    "properties": {
        "name": {
            "type": "string"
        },
        "phone": {
            "type": "integer"
        }
    },
    "required": [
        "name",
        "phone"
    ],
    "type": "object"
}

FIXME: this belongs in Data.OpenApi.Schema.Validation (in swagger2).

Provide a counterexample if there is any.