[derrickaw]

Problem: Importing gcpopts in gcsx and dataflowlib (#40686) transitively registers gcpopts's global --region and --project flags on flag.CommandLine, causing flag redefined panics in binaries that define their own --region or --project flags.

Fix: This PR removes the gcpopts dependency from gcsx and dataflowlib by:

• Moving GetUniverseDomain into a new flag-free util/gcpx package (sdks/go/pkg/beam/util/gcpx), which gcsx, dataflowlib, and other GCP packages can import without registering global flags.
• Moving GetGcsEndpoint to gcsx (using flag.Lookup("gcs_endpoint") instead of referencing *gcpopts.GcsEndpoint directly).
• Keeping delegating wrappers in gcpopts to preserve its public API.

#40730

[derrickaw]

/gemini review

[github-actions]

📋 Review Summary

This PR cleanly resolves global flag collisions (--region and --project) caused by importing gcpopts in gcsx and dataflowlib. By relocating GetUniverseDomain and GetGcsEndpoint (using flag.Lookup) to gcsx while retaining delegating wrappers in gcpopts, the change breaks the problematic transitive dependency while preserving backward compatibility.

🔍 General Feedback

• The package dependency direction (gcpopts -> gcsx) and use of flag.Lookup("gcs_endpoint") effectively prevent unintended registration of global flags on flag.CommandLine for consumers of gcsx and dataflowlib.
• Unit tests have been appropriately migrated and updated to cover both the core implementation in gcsx and the delegating wrappers in gcpopts.

---

💡 Tip: Comment /gemini review on this pull request to trigger a new Gemini code review.

[codecov]

Codecov Report

❌ Patch coverage is 88.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.42%. Comparing base (a8d6afd) to head (76e7846).
⚠️ Report is 61 commits behind head on master.

Files with missing lines	Patch %	Lines
sdks/go/pkg/beam/options/gcpopts/options.go	0.00%	2 Missing ⚠️
sdks/go/pkg/beam/util/gcsx/gcs.go	83.33%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #40729       +/-   ##
===========================================
- Coverage   80.04%   56.42%   -23.63%     
===========================================
  Files         490      872      +382     
  Lines       82916   154080    +71164     
===========================================
+ Hits        66373    86937    +20564     
- Misses      16543    65285    +48742     
- Partials        0     1858     +1858     

Flag	Coverage Δ
go	28.93% <88.00%> (?)

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[derrickaw]

Will fix CodeQL failure in another PR since its not related to this one.

[github-actions]

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[github-actions]

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[shunping]

LGTM, thanks!