Trigger page load listeners when no longer loading

[johnhughes1984]

Description (*)

Trigger JavaScript page load listeners to fire when document is no longer 'loading' rather than waiting until it is marked as 'complete' as this can lead to severe delays in rendering JavaScript content.

Fixed Issues (if relevant)

1. requirejs/domReady.js can severely delay rendering of content #22909: requirejs/domReady.js can severely delay rendering of content

Manual testing scenarios (*)

1. Add a non blocking asset to the page with a severe delay e.g. <img src="https://httpstat.us/404?sleep=10000" /> (I added this to Magento_Theme::html/absolute_footer.phtml)
2. Visit the homepage
3. The loading status indicator in the browser should be visible for at least the time set in the sleep value of the asset, however private / JavaScript content should render before this finishes (I used the Default welcome msg! text in the header to verify this)

Questions or comments

N/A

Contribution 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)
• All automated tests passed successfully (all builds are green)

[m2-assistant]

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[magento-cicd2]

All committers have signed the CLA.

[magento-engcom-team]

Hi @ihor-sviziev, thank you for the review.
ENGCOM-5305 has been created to process this Pull Request
✳️ @ihor-sviziev, could you please add one of the following labels to the Pull Request?

Label	Description
Auto-Tests: Covered	All changes in Pull Request is covered by auto-tests
Auto-Tests: Not Covered	Changes in Pull Request requires coverage by auto-tests
Auto-Tests: Not Required	Changes in Pull Request does not require coverage by auto-tests

[magento-engcom-team]

@johnhughes1984 thank you for contributing. Please accept Community Contributors team invitation here to gain extended permissions for this repository.

[ihor-sviziev]

Not sure if it’s possible to cover with some js tests, but would be really great

[DrewML]

@magento give me test instance

[magento-engcom-team]

Hi @DrewML. Thank you for your request. I'm working on Magento instance for you

[magento-engcom-team]

Hi @DrewML, here is your new Magento instance.
Admin access: https://pr-23313.instances.magento-community.engineering/admin
Login: admin Password: 123123q

[DrewML]

I added <img src="https://httpstat.us/404?sleep=10000" /> to the homepage content in the provided demo instance, and verified that:

1. mage-init content is no longer relying on the load event, but instead DOMContentLoaded as intended
2. That the specific conditional change in this PR was actually hit/executed during my testing

Thanks @johnhughes1984!

[engcom-Delta]

✔️ QA passed

[VladimirZaets]

Hi @ihor-sviziev. I think test coverage in this case not applicable. In general, we can cover the functionality of domReady by tests, but it's 3rd party library and it doesn't show real broken cases, we can check it just by functional tests that covered direct part of the functionality

[engcom-Alfa]

✔️ QA Passed

[DrewML]

@magento-engcom-team Anything pending before we can merge this?

[slavvka]

@magento run all tests

[slavvka]

The PR is currently in the delivery queue. Please be patient.

[VladimirZaets]

Please fix failed CE, EE, B2B FAT

[slavvka]

@magento run all tests

[ihor-sviziev]

@engcom-Golf @engcom-Foxtrot ,
Could you fix failing b2b / ee functional tests?

[m2-assistant]

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