set label filter to nil when it is empty string

internal/loader/configuraiton_setting_loader_test.go

@@ -1216,6 +1216,7 @@ func TestGetFilters(t *testing.T) {
 	two := "two"
 	three := "three"
 	labelString := "test"
+	emptyLabel := ""
 	testSpec := acpv1.AzureAppConfigurationProviderSpec{
 		Configuration: acpv1.AzureAppConfigurationKeyValueOptions{
 			Selectors: []acpv1.Selector{
@@ -1324,6 +1325,19 @@ func TestGetFilters(t *testing.T) {
 	assert.Equal(t, "test", *filters6[0].LabelFilter)
 	assert.Equal(t, "one", *filters6[1].KeyFilter)
 	assert.Nil(t, filters6[1].LabelFilter)
+
+	testSpec7 := acpv1.AzureAppConfigurationProviderSpec{
+		Configuration: acpv1.AzureAppConfigurationKeyValueOptions{
+			Selectors: []acpv1.Selector{
+				{KeyFilter: &one, LabelFilter: &emptyLabel},
+			},
+		},
+	}
+
+	filters7 := GetKeyValueFilters(testSpec7)
+	assert.Len(t, filters7, 1)
+	assert.Equal(t, "one", *filters7[0].KeyFilter)
+	assert.Nil(t, filters7[0].LabelFilter)
 }
 
 func TestCompare(t *testing.T) {

internal/loader/configuration_setting_loader.go

@@ -664,7 +664,15 @@ func deduplicateFilters(filters []acpv1.Selector) []acpv1.Selector {
 				}
 			}
 			if !findDuplicate {
-				result = append(result, filters[i])
+				labelFilter := filters[i].LabelFilter
+				// need to check if labelFilter is empty, if so, set it to nil
+				if labelFilter != nil && len(*labelFilter) == 0 {
+					labelFilter = nil
+				}
+				result = append(result, acpv1.Selector{
+					KeyFilter:   filters[i].KeyFilter,
+					LabelFilter: labelFilter,
+				})
 			}
 		}
 		reverse(result)