Move some code under filterListItems to decrease cyclomatic complexity

To eliminate:
pkg/cache/internal/cache_reader.go:91::warning: cyclomatic complexity 12 of function (*CacheReader).List() is high (> 10) (gocyclo)
pkg/client/fake/client.go:92::warning: cyclomatic complexity 12 of function (*fakeClient).List() is high (> 10) (gocyclo)

Author: ingvagabund

pkg/cache/internal/cache_reader.go

@@ -116,19 +116,30 @@ func (c *CacheReader) List(_ context.Context, opts *client.ListOptions, out runt
 		labelSel = opts.LabelSelector
 	}
 
+	filteredItems, err := c.filterListItems(objs, labelSel)
+	if err != nil {
+		return err
+	}
+
+	return apimeta.SetList(out, filteredItems)
+}
+
+func (c *CacheReader) filterListItems(objs []interface{}, labelSel labels.Selector) ([]runtime.Object, error) {
 	runtimeObjs := make([]runtime.Object, 0, len(objs))
 	for _, item := range objs {
 		obj, isObj := item.(runtime.Object)
 		if !isObj {
-			return fmt.Errorf("cache contained %T, which is not an Object", obj)
+			return nil, fmt.Errorf("cache contained %T, which is not an Object", obj)
 		}
 		runtimeObjs = append(runtimeObjs, obj)
 	}
+
 	filteredItems, err := objectutil.FilterWithLabels(runtimeObjs, labelSel)
 	if err != nil {
-		return err
+		return nil, err
 	}
-	return apimeta.SetList(out, filteredItems)
+
+	return filteredItems, nil
 }
 
 // objectKeyToStorageKey converts an object key to store key.

pkg/client/fake/client.go

@@ -24,6 +24,7 @@ import (
 	"strings"
 
 	"k8s.io/apimachinery/pkg/api/meta"
+	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/client-go/kubernetes/scheme"
@@ -116,18 +117,23 @@ func (c *fakeClient) List(ctx context.Context, opts *client.ListOptions, list ru
 	}
 
 	if opts.LabelSelector != nil {
-		objs, err := meta.ExtractList(list)
-		if err != nil {
-			return err
-		}
-		filteredObjs, err := objectutil.FilterWithLabels(objs, opts.LabelSelector)
-		if err != nil {
-			return err
-		}
-		err = meta.SetList(list, filteredObjs)
-		if err != nil {
-			return err
-		}
+		return filterListItems(list, opts.LabelSelector)
+	}
+	return nil
+}
+
+func filterListItems(list runtime.Object, labSel labels.Selector) error {
+	objs, err := meta.ExtractList(list)
+	if err != nil {
+		return err
+	}
+	filteredObjs, err := objectutil.FilterWithLabels(objs, labSel)
+	if err != nil {
+		return err
+	}
+	err = meta.SetList(list, filteredObjs)
+	if err != nil {
+		return err
 	}
 	return nil
 }