Fix CronFederatedHPA missing targetReplicas panic

[rootp1]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Summary

• add a defensive nil check in ScalingJob.ScaleWorkloads() so invalid direct workload scaling rules return an error instead of panicking
• add a regression test for a missing targetReplicas rule

Linked Issue

Fixes #7726

What Changed

• return a clear error when direct workload scaling is requested without targetReplicas
• cover the nil TargetReplicas path in cronfederatedhpa_job_test.go

Verification

• go test ./pkg/controllers/cronfederatedhpa — passed
• make test — passed
• make verify — not run cleanly: the target was executed twice; the first run failed because golangci-lint was installed into ~/go/bin but that path was not on PATH, and the rerun progressed further but failed in repository verification cleanup/codegen with existing API-rule output and permission errors removing the generated local _go toolchain directory

Scope

• only the CronFederatedHPA controller and its focused unit test were changed; unrelated files were not modified

Which issue(s) this PR fixes:

Fixes #7726

Special notes for your reviewer:

• make verify did not complete successfully in this local environment for reasons described above.

Does this PR introduce a user-facing change?:

NONE

[karmada-bot]

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Details

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• pkg/controllers/OWNERS

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a runtime panic in the CronFederatedHPA controller. By validating the presence of targetReplicas before attempting to scale workloads, the controller now gracefully handles misconfigured scaling rules by returning a descriptive error instead of crashing.

Highlights

• Bug Fix: Added a defensive nil check in ScalingJob.ScaleWorkloads to prevent panics when targetReplicas is missing.
• Regression Testing: Introduced a new unit test, TestScaleWorkloadsNilTargetReplicas, to verify that an appropriate error is returned when targetReplicas is nil.

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[gemini-code-assist]

Code Review

This pull request adds a nil check for TargetReplicas in the ScaleWorkloads function of the ScalingJob controller to prevent potential issues when scaling workloads. It also introduces a corresponding unit test TestScaleWorkloadsNilTargetReplicas to verify that an appropriate error is returned when TargetReplicas is nil. There are no review comments, so I have no additional feedback to provide.

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 42.06%. Comparing base (d01d3a8) to head (2213303).
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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7727   +/-   ##
=======================================
  Coverage   42.06%   42.06%           
=======================================
  Files         879      879           
  Lines       54831    54833    +2     
=======================================
+ Hits        23065    23067    +2     
+ Misses      30022    30021    -1     
- Partials     1744     1745    +1     

Flag	Coverage Δ
unittests	42.06% <100.00%> (+<0.01%)	⬆️

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