I've been using theclavier library for input validation, it works nicely but we could make it a bit more terse.

Let's say you are building many HTML forms. Doing one all manually is OK-ish, not two. You could usecl-forms (I didn't, I'm building a layer to get a form from Mito objects. If you didn't see where I'm doing it look better or stay tuned ;) ) You could do things semi-manually and use Clavier for input validation. It works like this.

Define a list of validators for your fields:

(defmethodvalidators((obj(eql'book)))(dict'isbn(list;; other validator here…(clavier:len:min10:max13;; :message works with clavier's commit of <2024-02-27>;; :message "an ISBN must be between 10 and 13 characters long"))'title(clavier:~="test""this title is too common, please change it!")))

You can compose them with boolean logic:

(defparameter*validator*(clavier:||(clavier:blank)(clavier:&&(clavier:is-a-string)(clavier:len:min10)))"Allow a blank value. When non blank, validate.")

This validator allows an input to be an empty string, but if it isn't, it validates it.

(funcall*validator*"");; =>TNIL(funcall*validator*"asdf");; =>NIL"Length of \"asdf\" is less than 10"

For one, I want a shorter construct for this common need.My PR was rejected so here it is.

Use a:allow-blank keyword:

(defmethodvalidators((obj(eql'book)))(dict'isbn(list:allow-blank(clavier:len:min10:max13…

and write avalidate-all function:

(defunvalidate-all(validatorsobject)"Run all validators in turn. Return two values: the status (boolean), and a list of messages.  Allow a keyword validator: :allow-blank. Accepts a blank value. If not blank, validate.";; I wanted this to be part of clavier, but well.;; https://github.com/mmontone/clavier/pull/10(let((messagesnil)(validt))(loopforvalidatorinvalidatorsif(and(eql:allow-blankvalidator)(str:blankpobject))returntelsedo(unless(symbolpvalidator)(multiple-value-bind(statusmessage)(clavier:validatevalidatorobject:error-pnil)(unlessstatus(setfvalidnil))(whenmessage(pushmessagemessages)))))(valuesvalid(reverse(uiop:ensure-listmessages)))))

This could be made better for a library API maybe? Anyways it works for now©.

See also that Clavier has a "validator-collection" thing, but not shown in the README, and is again too verbose in comparison to a simple list, IMO.

that's it, see ya next time.

Appendix: validators list:

This is the list of available validator classes and their shortcut function:

• equal-to-validator(==)
• not-equal-to-validator(~=)
• blank-validator(blank)
• not-blank-validator(not-blank)
• true-validator(is-true)
• false-validator(is-false)
• type-validator(is-a type)
• string-validator(is-a-string)
• boolean-validator(is-a-boolean)
• integer-validator(is-an-integer)
• symbol-validator(is-a-symbol)
• keyword-validator(is-a-keyword)
• list-validator(is-a-list)
• function-validator(fn function message)
• email-validator(valid-email)
• regex-validator(matches-regex)
• url-validator(valid-url)
• datetime-validator(valid-datetime)
• pathname-validator(valid-pathname)
• not-validator(~ validator)
• and-validator(&& validator1 validator2)
• or-validator(|| validator1 validator2)
• one-of-validator(one-of options)
• less-than-validator(less-than number)
• greater-than-validator(greater-than number)
• length-validator(len)
• :allow-blank (not merged, only in my fork)