Validators should return their success or failure

[BrucePerens]

Validators currently don't return a defined value. They should return true for valid and false for invalid. That way, we could run validators conditionally depending on the success of others. For example:

if validate_required(name)
  validate_size_of(name, 3, 12)
end

It would then also be possible to change validate_size_of, etc. to raise an exception if they are called upon a nil value, rather than silently ignoring it, which just seems wrong for validators.

[jwoertink]

I like that idea, though, not too sure about raising an exception. The actual error handling shouldn't be done in operations. That should be handled outside which is most likely the Action so that way the ErrorHandler picks it all up.

The only main thing to consider is if you have an attribute that is allowed to be nil, but you pass it to validate_size_of, what would that return? If it returns false, you might think it failed. Maybe it returns nil if it's ignored? 🤔

[BrucePerens]

What I want to do with the UI is something like this:

fail = if validate_required(password)
  if validate_length_of(password, 7, 24)
    ...
  end
end
if fail
  password.add_error <<-EOT
  A password should be between 7 and 24 characters in size,
  should contain at least one of each of a letter, a number,
  and a character that is neither a letter nor a number.
  EOT
end

[BrucePerens]

I am dubious about validators ignoring conditions that aren't true. Consider that validators with ! raise on nil:

if name.value
  validate_size_of!(name, 3, 12)
end