🐛 Fakeclient: Do not require ListKind

The fake client will currently error out of given a Kind in an
UnstructuredList that doesn't end with list. This is different from what
we do in the actual client, where we tolerate that:
https://github.com/kubernetes-sigs/controller-runtime/blob/10ae090c1d3ac0c560dfa1a29b2517eb8d74442b/pkg/client/unstructured_client.go#L204

This change brings the fake client in line with the real client.

pkg/client/fake/client.go

@@ -290,13 +290,11 @@ func (c *fakeClient) List(ctx context.Context, obj client.ObjectList, opts ...cl
 		return err
 	}
 
-	OriginalKind := gvk.Kind
+	originalKind := gvk.Kind
 
-	if !strings.HasSuffix(gvk.Kind, "List") {
-		return fmt.Errorf("non-list type %T (kind %q) passed as output", obj, gvk)
+	if strings.HasSuffix(gvk.Kind, "List") {
+		gvk.Kind = gvk.Kind[:len(gvk.Kind)-4]
 	}
-	// we need the non-list GVK, so chop off the "List" from the end of the kind
-	gvk.Kind = gvk.Kind[:len(gvk.Kind)-4]
 
 	listOpts := client.ListOptions{}
 	listOpts.ApplyOptions(opts)
@@ -311,7 +309,7 @@ func (c *fakeClient) List(ctx context.Context, obj client.ObjectList, opts ...cl
 	if err != nil {
 		return err
 	}
-	ta.SetKind(OriginalKind)
+	ta.SetKind(originalKind)
 	ta.SetAPIVersion(gvk.GroupVersion().String())
 
 	j, err := json.Marshal(o)

pkg/client/fake/client_test.go

@@ -129,6 +129,16 @@ var _ = Describe("Fake client", func() {
 			Expect(list.Items).To(HaveLen(2))
 		})
 
+		It("should be able to List using unstructured list when setting a non-list kind", func() {
+			By("Listing all deployments in a namespace")
+			list := &unstructured.UnstructuredList{}
+			list.SetAPIVersion("apps/v1")
+			list.SetKind("Deployment")
+			err := cl.List(context.Background(), list, client.InNamespace("ns1"))
+			Expect(err).To(BeNil())
+			Expect(list.Items).To(HaveLen(2))
+		})
+
 		It("should support filtering by labels and their values", func() {
 			By("Listing deployments with a particular label and value")
 			list := &appsv1.DeploymentList{}