[form.rule] Rename empty rule to be consistent

[mvorisek]

Feature Request

originally posted in atk4/ui#2129

Currently, the empty form rule is very, very confusing as the logic is negated with the remaining names.

empty means "nothing", but the rule validates the form field is "filled / not empty".

here atk4/ui#2129 (comment) is this fact more evident when compared with other rules like checked or is[dog]

This is a feature request to rename empty form rule to something like notEmpty or mandatory. For BC, the empty can be kept with a console warning.

[mvorisek]

I would be happy if the better named empty rule can be implemented in v2.9.x. The empty rule can be deprecated with a console warning (or whatever the minimal default verbosity level it). In v2.10.x, it can be removed or kept until v3.

[lubber-de]

Ok, i am preparing a PR. I thought about naming the new rule required instead of notEmpty?
This would at least fit the existing "autocheckRequired" functionality

Opinions?

[lubber-de]

Mmh, notEmpty would indeed fit better in the same terms as all the other rules, as the validation checks for "not empty" and not "if the field was required"....

[jamessampford]

Perhaps required should be added to ensure that there is a value of sorts (even a space)

notEmpty on the other hand could check that there is something useful there, but would need to trim the value to make sure that it isn’t just white space (space, tab, new line, etc)

There could possibly be use case where one needs to check that a field is empty with no value/whitespace. Such as do not complete this field if entered something elsewhere

[mvorisek]

Good points. I personally would prefer one function/name for "the 99% usecases", ie. a function that will check if the length is not zero after whitespaces are trimmed from the ends.

The reason I do not support additional function to check if an input is:

• strictly empty without trimming
• or "value is empty" like '0'

is that the first is not much useful in practice and the second is hard to define and basically any app needs a different criateria, like for some apps -1 is empty too. So user should define custom rule for these scenarious.

About the name, required or notEmpty LGTM, I have no preference.

[daveharris]

I've often wondered about this same issue, and came across this looking for something else. The negation issue is most-striking when sitting alongside other validations:

fields: {
  'host[first_name]': {
    rules: [
      { type: 'empty' },
      { type: 'maxLength[50]' },
    ]
  }

It appears the value needs to empty and less than 50 characters.

As for the name, coming from a Rails background, the presence validator has always made sense to me, so present would be my vote:

validates :first_name, presence: true, length: { maximum: 50 }

[mvorisek]

Thank you for supporting this issue, but present is NOT name I support nor frequently used by any common core, especially string, API.

[lubber-de]

I prepared that by #2949
Please take a look 😉

Edit: The trimming functionality is already inbuild via various possible "shouldTrim" setting (which is true by default)

[mvorisek]

Thank you all!