How to get JQuery Validation to call the remote rule on empty input

Question

How can I get JQuery Validation to fire the remote rule on an empty field? The server decides whether the field is required or not, so I need the remote rule to fire when calling valid even when the field is empty- currently, if the field is empty, the rule will not be called.

Answer 1

Created a new validator method which doesn't call the optional function and is setup to handle the ajax call as synchronous.

$.validator.addMethod("synchronousRemote", function (value, element, param) {

    var previous = this.previousValue(element);
    if (!this.settings.messages[element.name]) {
        this.settings.messages[element.name] = {};
    }
    previous.originalMessage = this.settings.messages[element.name].remote;
    this.settings.messages[element.name].remote = previous.message;

    param = typeof param === "string" && { url: param } || param;

    if (previous.old === value) {
        return previous.valid;
    }

    previous.old = value;
    var validator = this;
    this.startRequest(element);
    var data = {};
    data[element.name] = value;
    var valid = "pending";
    $.ajax($.extend(true, {
        url: param,
        async: false,
        mode: "abort",
        port: "validate" + element.name,
        dataType: "json",
        data: data,
        success: function (response) {
            validator.settings.messages[element.name].remote = previous.originalMessage;
            valid = response === true || response === "true";
            if (valid) {
                var submitted = validator.formSubmitted;
                validator.prepareElement(element);
                validator.formSubmitted = submitted;
                validator.successList.push(element);
                delete validator.invalid[element.name];
                validator.showErrors();
            } else {
                var errors = {};
                var message = response || validator.defaultMessage(element, "remote");
                errors[element.name] = previous.message = $.isFunction(message) ? message(value) : message;
                validator.invalid[element.name] = true;
                validator.showErrors(errors);
            }
            previous.valid = valid;
            validator.stopRequest(element, valid);
        }
    }, param));
    return valid;
}, "Please fix this field.");

Answer 2

If the field is empty, then there is no data to evaluate.

In other words, none of the validation rules (except for required) are fired when an input is empty... that's just how the plugin's methods are written.

However, the only way to change how the standard methods operate would be to over-ride them with your own. Use the .addMethod() method to write a new remote method that makes the field required. Look at the source code for the existing remote method and use that within your custom method. You'll need to remove any parts that utilize this.optional(element) as that's what keeps it from firing on empty input field.