✨ [RUM-10144] apply context defined just after init to View event generated during init

[BenoitZugmeyer]

Motivation

Usually, context (global/user/account/feature flags etc.) is defined just after calling RUM.init(), which is an issue because events that are generated during init() will not have this context.

This is only problematic for View events: RUM.init() generates a first View event that is missing the context defined right after. It is usually fine, as we can expect a RUM View Update to be generated at some point later. But sometimes no View Update happen for some reason (connectivity error, browser exiting abruptly...). In those cases, it is unexpected that the View isn't including the context.

Fixes #3935

Changes

This PR fixes this issue by slightly delaying the first View update. It uses Promise.resolve() to schedule a view update in the next micro task. It should not impact reliability as using Promise.resolve().then() to schedule a micro task is not impacted by timers throttling.

Please review commit by commit.

Test instructions

In the sandbox, define a user just after init():

      DD_RUM.init({
        clientToken: 'xxx',
        applicationId: 'xxx',
        ...
      })
      DD_RUM.setUser({ id: 'foo' })

Using the devtools extension, look at individual View events by unchecking Show only the latest View event in the "Events" tab.

When loading the sandbox URL, all View events should contain the @usr.id, even the very first View.

Checklist

• Tested locally
• Tested on staging
• Added unit tests for this change.
• Added e2e/integration tests for this change.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.39%. Comparing base (b3ee2b8) to head (2b6121e).
⚠️ Report is 587 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3597      +/-   ##
==========================================
+ Coverage   92.37%   92.39%   +0.01%     
==========================================
  Files         323      323              
  Lines        8135     8148      +13     
  Branches     1841     1842       +1     
==========================================
+ Hits         7515     7528      +13     
  Misses        620      620              

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[cit-pr-commenter]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	180.58 KiB	180.68 KiB	+98 B	+0.05%	✅
Rum Profiler	8.43 KiB	8.43 KiB	0 B	0.00%	✅
Rum Recorder	21.12 KiB	21.12 KiB	0 B	0.00%	✅
Logs	57.03 KiB	57.03 KiB	0 B	0.00%	✅
Rum Salesforce	N/A	138.49 KiB	N/A	N/A	N/A
Rum Slim	138.46 KiB	138.48 KiB	+18 B	+0.01%	✅
Worker	22.96 KiB	22.96 KiB	0 B	0.00%	✅
Rum Shopify	N/A	200.25 KiB	N/A	N/A	N/A
Rum-shopify Profiler	N/A	8.43 KiB	N/A	N/A	N/A
Rum-shopify Recorder	N/A	3.72 KiB	N/A	N/A	N/A

[BenoitZugmeyer]

/to-staging

[dd-devflow]

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2025-06-04 16:03:38 UTC ℹ️ Start processing command /to-staging

---

2025-06-04 16:03:48 UTC ℹ️ Branch Integration: starting soon, merge expected in approximately 17m43s (p90)

Commit 2b6121e26e will soon be integrated into staging-23.

---

2025-06-04 16:15:46 UTC ℹ️ Branch Integration: This commit was successfully integrated

Commit 2b6121e26e has been merged into staging-23 in merge commit 6826f9d5e7.

Check out the triggered pipeline on Gitlab 🦊

If you need to revert this integration, you can use the following command: /code revert-integration -b staging-23

[datadog-datadog-prod-us1]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 87.50%
• Overall Coverage: 77.21% (+0.00%)

_{This comment will be updated automatically if new data arrives.
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