Question

I have a login form in view, there is a name input has many validators:

object Users extends Controller {

    val loginForm = Form(tuple(
        "name" -> ( 
            nonEmptyText // (1)
            verifying ("Its length should >= 4", name=>{ println("#222");name.length>=4 }) // (2)
            verifying ("It should have numbers and letters", name=>{println("#333"); ...}) // (3)
        )
}

Then I don’t input anything, press submit, and I found the console prints:

#222
#333

That means all validators performed, and they have relationship:

(1) & (2) & (3)

But I hope they:

(1) && (2) && (3)

That means, if the name is empty, the later two validators will be ignored.

Is it possible in play2?

Answer 1

The default behavior is to apply all the constraints defined on a field.
However, you can define your own validation constraint that stops applying constraints on the first fail:

def stopOnFirstFail[T](constraints: Constraint[T]*) = Constraint { field: T =>
  constraints.toList dropWhile (_(field) == Valid) match {
    case Nil => Valid
    case constraint :: _ => constraint(field)
  }
}

It can be used like the following:

val loginForm = Form(
  "name" -> (text verifying stopOnFirstFail(
    nonEmpty,
    minLength(4)
  ))
)

scala> loginForm.bind(Map("name"->"")).errors
res2: Seq[play.api.data.FormError] = List(FormError(name,error.required,WrappedArray()))

scala> loginForm.bind(Map("name"->"foo")).errors
res3: Seq[play.api.data.FormError] = List(FormError(name,error.minLength,WrappedArray(4)))

scala> loginForm.bind(Map("name"->"foobar")).errors
res4: Seq[play.api.data.FormError] = List()

(Note that my implementation of stopOnFirstFail applies two times the failing constraint, so this one should not have side effects)