Woocommerce Checkout - Display custom inline error messages (including custom validation messages)

functions.php

<?php

/**
 * adds custom js file to handle inline error messages
 */

add_action( 'woocommerce_after_checkout_form', 'add_custom_validation_script', 20 );

function add_custom_validation_script() {
    wp_enqueue_script(
        'inline_validation_script',
        get_stylesheet_directory_uri() . '/js/inline-validation.js',
        ['jquery']
    );
}



/**
 * adds error message field element to get inline error messages working
 * 
 * @param array $fields
 * @param object $errors
 */

add_filter( 'woocommerce_form_field', 'add_inline_error_messages_element', 10, 4 );

function add_inline_error_messages_element( $field, $key, $args, $value ) {
    if ( strpos( $field, '</span>' ) !== false ) {
        $error = '<span class="js-custom-error-message" style="display:none"></span>';
        $field = substr_replace( $field, $error, strpos( $field, '</span>' ), 0);
    }

    return $field;
}



/**
 * process custom checkout validations
 *
 * @param array $fields
 * @param object $errors
 */

add_action('woocommerce_after_checkout_validation', 'custom_checkout_validations', 10, 2);

function custom_checkout_validations($data, $errors)
{
    $your_custom_checkout_field = filter_input(INPUT_POST, 'your_custom_input_field');
    
    // your custom validations goes here
    // this is an example to check for the length of the string
    if ( !empty($your_custom_checkout_field) && strlen($your_custom_checkout_field) > 50 ) {
        $errors->add('your_custom_input_field', __('This field needs to be max 50 chars', 'YourThemeName'));
    }

    // this loop adds a data array to all error messages which will be applied as a "data-error-for" HTML attribute
    // to read out the corresponding field ids with javascript and display the error messages inline
    foreach( $errors->errors as $original_key => $error ) {
        $field_key = $original_key;

        // filter and rewrite the field id for native woocommerce error messages with a key containing _required
        if(strpos($original_key, '_required') !== false) {
            $field_key = str_replace('_required','', $original_key);
            $error[0] = __('This is a required field', 'YourThemeName');
        }

        // switch out the old error messages with the ones including a spiced up data array
        // to display with javascript
        $errors->remove($original_key);
        $errors->add($original_key, trim($error[0]), ['error-for' => $field_key . '_field']);
    }
}

inline-validation.js

jQuery(function ($) {
    'use strict';

    addInlineMessages();

    // Implementation

    // Listen to js event
    $(document.body).on('updated_checkout', function() {
        addInlineMessages();
    });

    function addInlineMessages() {
        var woocommerceErrorsEl = $('.woocommerce-error');
        var woocommerceInlineErrorsEl = $('li[data-error-for]', woocommerceErrorsEl);
        var inlineErrorMessagesEl = $('.js-custom-error-message');

        // as we use ajax submitting hide old validation messages
        if(inlineErrorMessagesEl.length) {
            inlineErrorMessagesEl.hide();
        }

        if(woocommerceInlineErrorsEl.length) {
            woocommerceInlineErrorsEl.each(function () {
                var errorEl = $(this);
                var errorText = $.trim(errorEl.text());

                var targetFieldId = errorEl.data('error-for');

                if(errorText && targetFieldId) {
                    var targetFieldEl = $('#' + targetFieldId);
                    var errorMessageField = $('.js-custom-error-message', targetFieldEl);

                    if(targetFieldEl.length && errorMessageField.length) {
                        targetFieldEl.removeClass('woocommerce-validated');
                        targetFieldEl.addClass('woocommerce-invalid');

                        errorMessageField.text(errorText);
                        errorMessageField.show();
                        errorEl.hide();
                    }
                }
            });

            if(woocommerceInlineErrorsEl.filter(':visible').length === 0) {
                woocommerceErrorsEl.hide();

                if(inlineErrorMessagesEl.filter(':visible').length > 0) {
                    scrollToElement(inlineErrorMessagesEl.filter(':visible').first());
                }
            } else {
                $('li:not([data-error-for])', woocommerceErrorsEl).hide();
                scrollToElement(woocommerceErrorsEl);
            }

        }
    }

    function scrollToElement(el) {
        if(el.length) {
            $([document.documentElement, document.body]).animate({
                scrollTop: el.offset().top - 100
            }, 2000);
        }
    }

    // event listeners
    $(document.body).on('checkout_error', function (event) {
        jQuery('html, body').stop();

        addInlineMessages();
    });
});

Ok let me try

Ciao Luca, it doesn't work for me... I may have done something wrong though...

Same for me Lucas, the js file is loaded on checkout and error message is set. When .js-custom-error-message is manually set to display block you can see the error messages below the field. However they aren't toggled automatically when clicking place order with empty fields.

@lucasjahn this is amazing! Thank you for the help putting it together :)
Question - is it possible to apply this to the 'my account' forms section of WooCommerce? Default links for the below billing address and edit account forms
my-account/edit-address/billing/
my-account/edit-account/
Thanks!

Hey @jemsz so I think this should be possible but I'm right now not sure as you would have to adjust the validation function and when it triggers. Im thinking about to stuff this thing in a little plugin so maybe I could have a look at the my account validation as well.

Hello, is it possible to validate the custom checkbox field in your code? I have added a privacy policy agreement to my site, but I can't get it to show an inline error if the client doesn't check the field.

Privacy policy code: https://www.businessbloomer.com/woocommerce-additional-acceptance-checkbox-checkout/.

Thanks for your help!

@Z1pas this is totally possible. This is done in my code in the custom_checkout_validations function.

Basically you can add any validation you want and it will add it to the corresponding fields if it is created with the woocommerce_form_field method.

Anyway, I think I have to have a little overhaul of the code above as some people have some problems with it (probably due to other themes/plugins) enabled etc. but the basic I idea stays.

Cheers.

@lucasjahn thank you so much for your help and quick response. I finally validated my checkbox field! The code works perfectly!

All the best to you!

Hey there, I just wanted to ask i want to show radio button error which is required but its not visible even though i wrote code and in backend it is working its just not visible on frontend please if you can help me solve this issue.

add_filter( 'woocommerce_form_field', 'wtwh_checkout_fields_in_label_error', 10, 4 );

function wtwh_checkout_fields_in_label_error( $field, $key, $args, $value ) {

if ( strpos( $field, '</label>' ) !== false && $args['required'] ) {
    $error = '<span class="error" style="display:none">';
    $error .= sprintf( __( '%s is a required.', 'woocommerce' ), $args['label'], $args['radio'] );
    $error .= '</span>';
    // Append the error message inside the field
    $field = substr_replace( $field, $error, strpos( $field, '</label>' ) + strlen('</label>'), 0);
}

if ($args['type'] === 'radio' && $args['required']) {
    // Add the error message inside the radio button container
    $error = '<span class="error" style="display:none">';
    $error .= sprintf(__(' %s is a required field.', 'woocommerce'), $args['label']);
    $error .= '</span>';
    // Append the error message inside the field
    $field = str_replace('<input', $error . '<input', $field);
}
   
return $field;

}