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  • kmitov 6:28 pm on April 7, 2021 Permalink |
    Tags: , jquery, , rails-ujs, ,   

    From a ticket to deploy in an hour. jQuery runs the scripts, DOM does not. 

    (Everyday Code – instead of keeping our knowledge in a README.md let’s share it with the internet)

    This is an article of a production incidents with Rails/Stimulus/Rails-ujs/DOM and jQuery.

    We made mistake that made us lose 31 registrations on the FLLCasts and a few more on the BuildIn3D platform. The stack involved includes Ruby on Rails with Rails-ujs, Stimulus, DOM and jQuery. I will enter into some details about how it occurred, why and how we resolved it in under an hour. I am writing this article mainly to share with my our team, but I am sure it could be useful for other teams.

    FLLCasts registration form as of April 2021

    The incident – people could not Sign Up on the platforms

    On the Sign up page there is a captach. Years ago we found our that the captcha helps us reduce invalid registartion.
    There is also one more thing on this platform – usernames. As the FLLCasts platforms is used by students and academies, one of the very useful features on the platform is the automatically generated username. Users type their names in the “Full name” field and a username is automatically generated for them. In this way there is a unique username for users because email is not unique – there could be many users with the same email.

    To generate a new username we send a request to the server and refresh form. We use Stimulus and rails-ujs for this.

    The is an “change->registrations#refreshForm” for the input field for the name. When the full name is changed the form is refreshed and a unique username is returned from the server.

    <%= user_form.fields_for :data, {parent_builder: user_form} do |data_form| %>
      <%= data_form.text_field :name_attribute,
          icon_prepend: "icon-finance-067 u-line-icon-pro",
          autofocus: true,
          data: {
            registrations_target: "name",
            action: "change->registrations#refreshForm"
          autocomplete: "off"
      <%= data_form.email_field :email %>
    <% end %>

    Here is how it should work:

    How the form is supposed to work

    The incident was that when the form was refresh the captcha got lost and we were not showing it after that. This means that on the server we were checking the captcha, but there was not captcha on the client.

    The ticket

    A wild ticket appears from a user.

    We wanted to enroll our Kid for Personal B programme and we were trying to Sign Up to pay online , but we are unable to sign up using our details.
    We get an error message though we tried a few times.
    Please help to sort this out.

    This is a really wild ticket. The user wants to buy and they can not sign up. 1,2,3 go.

    The problem

    We’ve made the following commit in the registration form

    --- a/app/views/devise/registrations/new.js.erb
    +++ b/app/views/devise/registrations/new.js.erb
    @@ -1 +1 @@
    -$("#<%= @form_id %>").replaceWith("<%= escape_javascript(render 'form') %>")
    \ No newline at end of file
    +document.getElementById("<%=form_id%>").outerHTML= '<%= escape_javascript(render "#{partial_name}") %>';
    \ No newline at end of file

    We are in the process of removing jQuery from the code. I saw this jQueyr call and decided to change it to a simple DOM call. It should be the same, right? No…

    jQuery executes scrips while document.outerHTML does not

    I knew this. But I did not consider it in this commit. What happens is that we receive the new form from the server and replace the form on the page with the new form received from the server that contains the generate username.

    But in this form (and this form only on the whole platform) there is a recaptach. This recaptcha is a JavaScript and when dynamically changing the DOM the JavaScript must be executed. Well, jQuery automatically executed this for us. document.outerHTML does not.

    Developing and RSpec system spec.

    First I deployed the fix to production. It took about 5 minutes.

    After that I developed the spec. This is how the spec looks like:

    scenario "shows recaptach when dynamically reloading the form", js: true  do
        with_recaptcha_enabled do
          expect(page).to have_recaptcha
          name_field.set unique_name
          email_field.set "#{SecureRandom.hex(16)}@example.com"
          # This means we have reloaded with js because we've set the email field 
          # and this has change the focus and there was a fire event for the name_field.
          # We are now waiting for the username to appear on the screen
          expect(page).to have_username_filled
          expect(page).to have_recaptcha

    We expect that there is a recaptcha before and after refreshing the form.

    What surprised us

    Looking at the data in the time frame this commit was on production – we’ve received 9 registrations on the platform. In the same previous period we’ve receive 40 registrations.

    This means that we’ve lost 31 registrations on the platform.

    What surprised us is that 9 people managed to register. The only way you could register on the platform during this period is to first enter your username. If you enter the username on your own we do not refresh the form as we don’t have to generate a username for you. This means that about 25% of the people start with their username and about 75% of the users at FLLCasts start the registration with their name or email.

    Good to know. Good to know.


    Looking at the issue we could have prevented it in a number of ways. In a test environment it is difficult to have a recaptcha because there is no way to test that the recaptcha works. After all that is the whole purpose of a recaptcha – to prevent bots and a Selenium driver is exactly a bot. But it turned out we’ve missed it as a scenario in the specs. It is always a missing spec.

  • kmitov 1:03 pm on April 22, 2020 Permalink |
    Tags: , jquery, , , , ,   

    Rails 6 + webpacker + jquery + sprockets + jquery plugin (fancetree) 

    So you might be in the process of migrating to webpacker. This means your sprockets should continue working. This is difficult. Sprockets wants jquery available in the view and you don’t have jquery available in the views. You have it in the webpacker packs.

    These things won’t work


    jQuery is only available to the PACKS it is not available to the VIEWS.

    But there is a solution – expose-loader

    Here is how to setup jquery to be available to the views in sprockets app that you are migrating to rails 6. I am starting from the previous article were we set up the project from 0. – https://kmitov.com/posts/rails-6-webpacker-yarn-fancytree-less/

    $ yarn add expose-loader

    Add configuration for exposing of jquery

    // config/webpack/environments.js
    const { environment } = require('@rails/webpacker')
    const less_loader= {
     test: /\.less$/,
     use: ['css-loader', 'less-loader']
    environment.loaders.append('less', less_loader)
    +const webpack = require('webpack')
    +// this makes jquery available in all pack and you don't
    +// have to import or require it each time 
    +  'Provide',
    +  new webpack.ProvidePlugin({
    +    $: 'jquery',
    +    jQuery: 'jquery'
    +  })
    +// this exposes jquery to be available in the views
    +// <script>
    +//   console.log($('#tree'))
    +// </script>
    +environment.loaders.append('expose', {
    +  test: require.resolve('jquery'),
    +  use: [{
    +    loader: 'expose-loader',
    +    options: '$'
    +  }, {
    +    loader: 'expose-loader',
    +    options: 'jQuery',
    +  }]

    Also expose fancytree

    // config/webpack/environments.js
    +// this exposes fancytree to be available in the views
    +// <script>
    +//   console.log($('#tree').fancytree())
    +// </script>
    +environment.loaders.append('fancytree', {
    +  test: require.resolve('jquery.fancytree'),
    +  use: [{
    +    loader: 'expose-loader',
    +    options: 'fancytree'
    +  }]

    And you are done.

    How in your views you could do:

          extensions: ['edit', 'filter'],
          source: [
            {title: "Node 1", key: "1"},
            {title: "Folder 2", key: "2", folder: true, children: [
              {title: "Node 2.1", key: "3"},
              {title: "Node 2.2", key: "4"}
        const tree = fancytree.getTree('#tree');
        // Note: Loading and initialization may be asynchronous, so the nodes may not be accessible yet.

    Fancytree as a jquery plugin is working in rails 6 views and is available also to sprockets compiled files.

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