[confmap] fix bug of unmarshalling slice values

[fatsheep9146]

Description:
fix the bug of unmarshalling slice values for package confmap

Link to tracking Issue:
fix #4001

[codecov]

Codecov Report

Patch coverage is 70.00% of modified lines.

Files Changed	Coverage
confmap/confmap.go	70.00%

📢 Thoughts on this report? Let us know!.

[fatsheep9146]

@dmitryax could you help review this pr?

[dmitryax]

Please address comments from @bogdandrutu in #6163. I think we should not override with nil but probably should override with []

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 14 days.

[fatsheep9146]

Please address comments from @bogdandrutu in #6163. I think we should not override with nil but probably should override with []

@dmitryax

I think it is already doing like that, in unit test, these two cases are also covered

opentelemetry-collector/confmap/confmap_test.go

Lines 449 to 472 in 4dc71d6

	{
	name: "overridden by an empty slice",
	cfg: map[string]any{
	"strings": []string{},
	},
	provided: &structWithSlices{
	Strings: []string{"xxx", "yyyy"},
	},
	expected: &structWithSlices{
	Strings: []string{},
	},
	},
	{
	name: "not overridden by nil",
	cfg: map[string]any{
	"strings": nil,
	},
	provided: &structWithSlices{
	Strings: []string{"xxx", "yyyy"},
	},
	expected: &structWithSlices{
	Strings: []string{"xxx", "yyyy"},
	},
	},

• The default value will not be overrided by nil.
• The default value will be overrided by [] empty slice.

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 14 days.

[fatsheep9146]

still doing

[fatsheep9146]

@open-telemetry/collector-maintainers
could you help review about this pr?

[codeboten]

Thanks for including the detailed documentation @fatsheep9146