Clear Flask-WTF after AJAX submission

gistfile1.txt

# =============================================================================
# routes.py
# =============================================================================
@bp.route('/add_child_product', methods=['POST'])
def add_child_product():
    """
    Handle form validation. If form is invalid, re-render form with validation
    errors. If the form is valid, update product spec table, close modal and 
    reset form.
    """
    
    new_child_form = NewChildForm()
    
    if new_child_form.validate_on_submit():
        parent_code = new_child_form.parent_product_code.data
        
        # Process form here
        
        # Reset the form
        new_child_form.reset()
        
        return jsonify({'template': render_template(
                          PROD_SPEC + 'product_specifications.html',
                          new_child_form=new_child_form,
                          product_code=parent_code,
                          success=True), # In place of flash
                        'success': True})
    else:
        return jsonify({'template': render_template(
                          PROD_SPEC + 'new_child_form.html',
                          new_child_form=new_child_form,
                          product_code=new_child_form.parent_product_code.data,
                          success=False
                          ),
                        'success': False})

# =============================================================================
# forms.py
# =============================================================================
from werkzeug.datastructures import MultiDict

class NewChildForm(FlaskForm):
    parent_product_code = HiddenField()
    new_product_code = IntegerField('Product Code', 
                                    validators=[DataRequired()])
    product_qty = FloatField('Child Quantity', validators=[DataRequired()])
    submit = SubmitField('Add Child')
    
    # Validation methods here
    
    def reset(self):
        """
        Reset all fields and avoid validation errors, but pre-populate hidden 
        field
        """
        blank_data = MultiDict([('parent_product_code', 
                                self.parent_product_code)])
        self.process(blank_data)
        
# =============================================================================
# template.html
# =============================================================================
<script>
$("#add_new_child").submit(function(e) {
    e.preventDefault();
    var form = $(this);
    var url = form.attr('action');
    
    // Avoid CSRF issues by not including token in the form itself
    var csrf_token = "{{ csrf_token() }}";
    
    $.ajaxSetup({
        beforeSend: function(xhr, settings) {
            if (!/^(GET|HEAD|OPTIONS|TRACE)$/i.test(settings.type) && !this.crossDomain) {
                xhr.setRequestHeader("X-CSRFToken", csrf_token);
            }
        }
    });
    $.ajax({
        type: "POST",
        url: url,
        data: form.serialize(),
        context: form,
        success: function(resp) {
            if (resp['success'] == true) {
                $('#product_spec_div').html(resp['template']);
                $(".modal-fade").modal("hide");
                $('body').removeClass('modal-open');
                $(".modal-backdrop").remove();
            } else {
                $('#form_new_child').html(resp['template']);
            }
        }
    });
});
</script>