♻️ [RUM-9614] Decouple default context from assembly using hooks

[amortemousque]

Motivation

Decouple the default context from the assembly. The 'default context' includes the following data:

 _dd: {
  format_version: 2,
  drift: currentDrift(),
  configuration: {
    session_sample_rate: round(configuration.sessionSampleRate, 3),
    session_replay_sample_rate: round(configuration.sessionReplaySampleRate, 3),
  },
  browser_sdk_version: canUseEventBridge() ? __BUILD_ENV__SDK_VERSION__ : undefined,
},
application: {
  id: configuration.applicationId,
},
date: timeStampNow(),
source: 'browser',

Changes

• Create a defaultContext module that uses assemble hook
• Remove default context from assembly

Testing

• Local
• Staging
• Unit
• End to end

---

I have gone over the contributing documentation.

[BenoitZugmeyer]

Amazing

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 97.56098% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.22%. Comparing base (ee44e41) to head (3611819).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
...ges/rum-core/src/domain/action/actionCollection.ts	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3498      +/-   ##
==========================================
+ Coverage   92.17%   92.22%   +0.04%     
==========================================
  Files         312      313       +1     
  Lines        8043     8053      +10     
  Branches     1819     1820       +1     
==========================================
+ Hits         7414     7427      +13     
+ Misses        629      626       -3     

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[cit-pr-commenter]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	145.27 KiB	145.36 KiB	88 B	+0.06%	✅
Rum Recorder	18.02 KiB	18.02 KiB	0 B	0.00%	✅
Rum Profiler	4.64 KiB	4.64 KiB	0 B	0.00%	✅
Logs	49.96 KiB	49.96 KiB	0 B	0.00%	✅
Rum Slim	104.85 KiB	104.93 KiB	83 B	+0.08%	✅
Worker	23.59 KiB	23.59 KiB	0 B	0.00%	✅

🚀 CPU Performance

Action Name	Base Average Cpu Time (ms)	Local Average Cpu Time (ms)	𝚫
addglobalcontext	0.002	0.003	0.001
addaction	0.039	0.088	0.049
addtiming	0.001	0.001	0.000
adderror	0.041	0.054	0.013
startstopsessionreplayrecording	0.007	0.014	0.007
startview	0.388	0.554	0.165
logmessage	0.020	0.024	0.005

🧠 Memory Performance

Action Name	Base Consumption Memory (bytes)	Local Consumption Memory (bytes)	𝚫 (bytes)
addglobalcontext	24.93 KiB	25.80 KiB	891 B
addaction	52.02 KiB	56.70 KiB	4.67 KiB
addtiming	23.73 KiB	25.41 KiB	1.69 KiB
adderror	55.22 KiB	58.27 KiB	3.05 KiB
startstopsessionreplayrecording	22.47 KiB	25.26 KiB	2.78 KiB
startview	426.71 KiB	426.20 KiB	-522 B
logmessage	52.32 KiB	57.91 KiB	5.59 KiB

🔗 RealWorld

[BenoitZugmeyer]

thought: The non-null assertion we wanted to avoid seemed better than this {} as PartialRumEvent cast.

With the former, we acknowledge‏ that although triggerHook can return undefined in theory, it can't happen in assembly.ts. We also assume the PartialRumEvent is in fact a valid RUM event with all the required properties defined.

With the latter, we return an empty object, which is not only incorrect from a type perspective (PartialRumEvent expect to have a type property), but also doesn't improve the situation in assembly.ts as we'll still need to implicitly assume that it won't return an empty object.

[amortemousque]

/to-staging

[dd-devflow]

View all feedbacks in Devflow UI.

2025-05-06 13:29:39 UTC ℹ️ Start processing command /to-staging

---

2025-05-06 13:29:53 UTC ℹ️ Branch Integration: starting soon, merge expected in approximately 0s (p90)

Commit 3611819207 will soon be integrated into staging-19.

---

2025-05-06 13:44:52 UTC ℹ️ Branch Integration: This commit was successfully integrated

Commit 3611819207 has been merged into staging-19 in merge commit dfc1c59dab.

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-19