♻️ [RUM-8319] Use assembly hook for action

[amortemousque]

Motivation

The overall goal is to create a Modular SDK to simplify contributions and enhance extensibility.
This PR uses the assemble hook to decouple action assembly

Changes

Testing

• Local
• Staging
• Unit
• End to end

---

I have gone over the contributing documentation.

[cit-pr-commenter]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	146.36 KiB	146.40 KiB	43 B	+0.03%	✅
Logs	51.06 KiB	51.06 KiB	0 B	0.00%	✅
Rum Slim	105.14 KiB	105.18 KiB	43 B	+0.04%	✅
Worker	24.50 KiB	24.50 KiB	0 B	0.00%	✅

🚀 CPU Performance

Action Name	Base Average Cpu Time (ms)	Local Average Cpu Time (ms)	𝚫
addglobalcontext	0.002	0.002	0.000
addaction	0.035	0.035	0.001
addtiming	0.001	0.001	-0.000
adderror	0.051	0.053	0.002
startstopsessionreplayrecording	0.007	0.010	0.003
startview	0.379	0.388	0.010
logmessage	0.019	0.028	0.009

🧠 Memory Performance

Action Name	Base Consumption Memory (bytes)	Local Consumption Memory (bytes)	𝚫 (bytes)
addglobalcontext	29.33 KiB	27.71 KiB	-1667 B
addaction	58.79 KiB	56.78 KiB	-2061 B
addtiming	27.00 KiB	26.91 KiB	-92 B
adderror	60.40 KiB	59.56 KiB	-869 B
startstopsessionreplayrecording	27.94 KiB	24.31 KiB	-3723 B
startview	419.39 KiB	419.30 KiB	-88 B
logmessage	65.40 KiB	57.97 KiB	-7603 B

🔗 RealWorld

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 93.64%. Comparing base (1e6be41) to head (46c2b56).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...ges/rum-core/src/domain/action/actionCollection.ts	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3305      +/-   ##
==========================================
- Coverage   93.71%   93.64%   -0.08%     
==========================================
  Files         291      291              
  Lines        7670     7676       +6     
  Branches     1747     1751       +4     
==========================================
  Hits         7188     7188              
- Misses        482      488       +6     

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[sethfowler-datadog]

LGTM!

[sethfowler-datadog]

The event will already have a type property, right? Assuming that's true, it may make sense to only have the hook return the properties it's adding or changing.

[amortemousque]

You're right! Specifying the type is a bit of an ugly hack to improve type checking 😞. See

browser-sdk/packages/rum-core/src/hooks.ts

Line 16 in 61fda30

// Ensuring the `type` field is always present improves type checking, especially in conditional logic in hooks (e.g., `if (eventType === 'view')`).

[amortemousque]

Happy to discuss a better alternative :)