Ensure children do not become orphans

[fredden]

Description

There is a bug in PageBuilder where child content nodes are going missing. These exist and work just fine when the content is first created, and saved, and shows correctly on the front-end. However, when the form is re-rendered in the admin, the children have been deleted, so saving the page/content a second time deletes these content nodes.

This is because the list of child nodes is replaced rather than added to when walking the node tree.

Manual testing scenarios

1. Create a new content type with a master template which has several siblings HTML nodes. For example,

<section class="pagebuilder-windmill" attr="data.main.attributes" ko-style="data.main.style" css="data.main.css">
  <div class="wrapper">
    <render args="masterTemplate" ></render>
  </div>

  <div class="pagination" if="data.main.attributes()['data-show-dots']"></div>

  <if args="data.main.attributes()['data-show-arrows']">
    <div class="button-prev"></div>
    <div class="button-next"></div>
  </if>

  <div class="scrollbar" if="data.main.attributes()['data-show-scrollbar']"></div>
</section>

2. Create a new Page in the admin and use this new content type.
3. Populate the content type with some child nodes (which will show up in the preview & on the front-end where we have the <render /> tag)
4. Save (and close) the page in the admin.
5. Check all is well on the front-end.
6. Click "edit" the same page in the admin, make no changes, click "save".
7. Observe the content has been erased by viewing the front-end and/or the admin.

Checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)

[hc-sven]

When will this be merged? This is a real issue. I can confirm that this change fixes the problem!

(We added a module to overwrite the stage-builder.js file for now)

[paras89]

@magento run all tests

[magento-automated-testing]

The requested builds are added to the queue. You should be able to see them here within a few minutes. Please re-request them if they don't show in a reasonable amount of time.

[magento-automated-testing]

The requested builds are added to the queue. You should be able to see them here within a few minutes. Please re-request them if they don't show in a reasonable amount of time.

[engcom-Hotel]

@magento run all tests

[engcom-Hotel]

Hello @fredden,

Thanks for the collaboration!

The Changes seem good to me but can you please cover the changes with some automated tests?

Thanks

[engcom-Hotel]

@magento run Functional Tests EE, WebAPI Tests

[engcom-Hotel]

@magento run all tests

[engcom-Hotel]

@magento run WebAPI Tests, Unit Tests, Performance Acceptance Tests, Integration Tests, Functional Tests EE, Functional Tests CE, Functional Tests B2B

[engcom-Hotel]

Hello @fredden,

We have tried to reproduce the issue in the latest development branch ie 2.4-develop but it seems the issue is not reproducible for us.

For reference, we are attaching the custom module through which we have tried to reproduce the issue:
Magz.zip

Let us know if we missed anything.

Thanks