operator/pkg: mitigate null pointer dereference in `Validate()` and `newRunData()` functions

[mohamedawnallah]

Description

In this commit, we mitigate the null pointer dereference issue in the deinit operator pkg by adding defensive checks on opt.Karmada.Spec.HostCluster in newRunData func and on opt.Karmada.Spec.Components in Validate in init.go.

Motivation and Context

While unit testing the Karmada Init and DeInit in the operator package (#5613), deliberately passing empty components on those fields triggers a null pointer exception error. This PR resolves this issue by adding defensive checks.

While testing

What type of PR is this?

/kind cleanup

Does this PR introduce a user-facing change?:

NONE

[mohamedawnallah]

Hey @chaosi-zju,

Just checking in on this PR. Any feedback you might have would be greatly appreciated!

It looks like PR #5613 is waiting on this one. Thanks!

[RainbowMango]

@mohamedawnallah Could you please rebase this PR? There is a conflict needs to be resolved. Also, what's the benefit of this? Only for ease of the unit tests?

cc @zhzhuang-zju @jabellard

[zhzhuang-zju]

While unit testing the Karmada Init and DeInit in the operator package (https://github.com/karmada-io/karmada/pull/5613), deliberately passing empty components on those fields triggers a null pointer exception error. This PR resolves this issue by adding defensive checks.

https://github.com/karmada-io/karmada/blob/c31c8e4a58430bc8bdf4b28fa7232dffbc3fce49/operator/pkg/apis/operator/v1alpha1/register.go#L49-L54

We registered a method in the init function to set default values for Karmada, which will be invoked when Default() is called. So in practice, there won’t be any null pointer issues because Default() is called before this code segment. When writing unit tests (UT), calling operatorscheme.Scheme.Default(karmada) can achieve the same effect.

Of course, adding some defensive checks can also prevent panics in case operatorscheme.Scheme.Default(karmada) is not called correctly in the code.

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[mohamedawnallah]

It looks like some of those defensive checks already added in that PR #5814. Updated this PR to handle when karmada *operatorv1alpha1.Karmada is nil and when opt.Karmada.Spec.HostCluster is nil part of newRunData.

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Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 48.42%. Comparing base (2f6ff56) to head (05ac259). Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
operator/pkg/init.go	0.00%	5 Missing :warning:
operator/pkg/controller/karmada/validating.go	0.00%	3 Missing :warning:

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5617      +/-   ##
==========================================
+ Coverage   48.27%   48.42%   +0.14%     
==========================================
  Files         677      677              
  Lines       56067    56074       +7     
==========================================
+ Hits        27068    27153      +85     
+ Misses      27229    27139      -90     
- Partials     1770     1782      +12     

Flag	Coverage Δ
unittests	48.42% <0.00%> (+0.14%)	:arrow_up:

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