Adding Bootstrap Forms to WooCommerce

gistfile1.php

add_filter('woocommerce_billing_fields', 'custom_woocommerce_billing_fields');

function custom_woocommerce_billing_fields( $fields ) {
  $fields['billing_address_1']['class'] = array( 'form-group' );
  $fields['billing_address_1']['input_class'] = array( 'form-control' );
  return $fields;
}

try this

add_filter('woocommerce_form_field_args',  'wc_form_field_args',10,3);
  function wc_form_field_args($args, $key, $value) {
  $args['input_class'] = array( 'form-control' );
  return $args;
}

Adding this for ages– builds upon the previous examples, hitting every input and adding form-group to the container, and form-control to the input. It also appends to the class arrays instead of overwrites, this might help avoid plugin conflicts.

add_filter('woocommerce_form_field_args', function ($args, $key, $value) {
    $args['input_class'][] = 'form-control';
    $args['class'][] = 'form-group';
    return $args;
}, 10, 3);

This is great, but only applies to the actual checkout - is there a straightforward way at all of doing this sitewide?