Validate email one-liner in Scala

As I've tested your regex and it was catching simple emails, I then checked your code and saw that you're using findFirstIn. I believe that is your problem. findFirstIn will jump all the spaces until it matches some sequence anywhere in the string. I believe that in your case it's better to use unapplySeq and check if it returns Some List

def isValid(email: String): Boolean =
   if("""(?=[^\s]+)(?=(\w+)@([\w\.]+))""".r.findFirstIn(email) == None)false else true

def isValid2(email: String): Boolean =
  """(\w+)@([\w\.]+)""".r.unapplySeq(email).isDefined

isValid("[email protected]")                        //> res0: Boolean = true

isValid("t es t@gmailcom")                       //> res1: Boolean = true

isValid("b ob @tes tmai l.com")                  //> res2: Boolean = false

isValid2("[email protected]")                       //> res3: Boolean = true

isValid2("t es t@gmailcom")                      //> res4: Boolean = false

isValid2("b ob @tes tmai l.com")                 //> res5: Boolean = false

// but those don't work for both:
// I recommend you using a proper regex pattern to match emails
isValid("[email protected]")                    //> res6: Boolean = true

isValid("test@gmailcom")                         //> res7: Boolean = true

isValid2("[email protected]")                   //> res8: Boolean = true

isValid2("test@gmailcom")                        //> res9: Boolean = true

My function is inspired from the one that the Play Framework uses (see PlayFramework) and uses the regexp presented here: W3C recommendation. Hope it helps. All tests suggested in the other questions are passed.

private val emailRegex = """^[a-zA-Z0-9\.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$""".r


def check(e: String): Boolean = e match{
    case null                                           => false
    case e if e.trim.isEmpty                            => false
    case e if emailRegex.findFirstMatchIn(e).isDefined  => true
    case _                                              => false
}