Cannot validate values of type "NULL" automatically

[norkunas]

When calling a collection post operation and if forgot to include a body then the api should handle this gracefully and return a 400 error instead of 500.

Currently it tries to validate "null" because controller result is null and symfony validator obviously doesn't like it.

Response from api:

{  
   "@context":"\/contexts\/Error",
   "@type":"hydra:Error",
   "hydra:title":"An error occurred",
   "hydra:description":"Cannot validate values of type \u0022NULL\u0022 automatically. Please provide a constraint."
}

[soyuka]

Duplicate: #1282

[teohhanhui]

See #2757

[jsawicki-internetcompany]

I had the same problem, and solved it by disabling the validation with validate=false in the custom operation in the entity.

 *        "my_custom_operation"={
 *              "input"=MyCustomInput::class,
 *              "method"="POST",
 *              "path"="/an_entity/something",
 *              "controller"=MyCustomAction::class,
 *              "validate"=false,
 *              "normalization_context"={
 *                  "groups"={
 *                      "groupA:read",
 *                  }
 *              },
 *              "denormalization_context"={
 *                  "groups"={
 *                      "groupB:update",
 *                  }
 *              },
 *              "validation_groups"={
 *                  "Default",
 *                  "groupB:update",
 *              }
 *          },