Merge pull request #62448 from k82cn/k8s_62002

Automatic merge from submit-queue (batch tested with PRs 62448, 59317, 59947, 62418, 62352). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Removed no-empty validation of nodeSelectorTerm.matchExpressions.

Signed-off-by: Da K. Ma <klaus1982.cn@gmail.com>

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
part of #62002

**Release note**:

```release-note
Pod affinity `nodeSelectorTerm.matchExpressions` may now be empty, and works as previously documented: nil or empty `matchExpressions` matches no objects in scheduler.
```

Author: Kubernetes Submit Queue

pkg/apis/core/validation/validation.go

@@ -3005,9 +3005,6 @@ func ValidateNodeSelectorRequirement(rq core.NodeSelectorRequirement, fldPath *f
 func ValidateNodeSelectorTerm(term core.NodeSelectorTerm, fldPath *field.Path) field.ErrorList {
 	allErrs := field.ErrorList{}
 
-	if len(term.MatchExpressions) == 0 {
-		return append(allErrs, field.Required(fldPath.Child("matchExpressions"), "must have at least one node selector requirement"))
-	}
 	for j, req := range term.MatchExpressions {
 		allErrs = append(allErrs, ValidateNodeSelectorRequirement(req, fldPath.Child("matchExpressions").Index(j))...)
 	}

pkg/apis/core/validation/validation_test.go

@@ -6069,6 +6069,47 @@ func TestValidatePod(t *testing.T) {
 				},
 			),
 		},
+		{ // Serialized node affinity requirements.
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      "123",
+				Namespace: "ns",
+			},
+			Spec: validPodSpec(
+				// TODO: Uncomment and move this block and move inside NodeAffinity once
+				// RequiredDuringSchedulingRequiredDuringExecution is implemented
+				//		RequiredDuringSchedulingRequiredDuringExecution: &core.NodeSelector{
+				//			NodeSelectorTerms: []core.NodeSelectorTerm{
+				//				{
+				//					MatchExpressions: []core.NodeSelectorRequirement{
+				//						{
+				//							Key: "key1",
+				//							Operator: core.NodeSelectorOpExists
+				//						},
+				//					},
+				//				},
+				//			},
+				//		},
+				&core.Affinity{
+					NodeAffinity: &core.NodeAffinity{
+						RequiredDuringSchedulingIgnoredDuringExecution: &core.NodeSelector{
+							NodeSelectorTerms: []core.NodeSelectorTerm{
+								{
+									MatchExpressions: []core.NodeSelectorRequirement{},
+								},
+							},
+						},
+						PreferredDuringSchedulingIgnoredDuringExecution: []core.PreferredSchedulingTerm{
+							{
+								Weight: 10,
+								Preference: core.NodeSelectorTerm{
+									MatchExpressions: []core.NodeSelectorRequirement{},
+								},
+							},
+						},
+					},
+				},
+			),
+		},
 		{ // Serialized pod affinity in affinity requirements in annotations.
 			ObjectMeta: metav1.ObjectMeta{
 				Name:      "123",
@@ -6517,26 +6558,6 @@ func TestValidatePod(t *testing.T) {
 				}),
 			},
 		},
-		"invalid requiredDuringSchedulingIgnoredDuringExecution node selector term, matchExpressions must have at least one node selector requirement": {
-			expectedError: "spec.affinity.nodeAffinity.requiredDuringSchedulingIgnoredDuringExecution.nodeSelectorTerms[0].matchExpressions",
-			spec: core.Pod{
-				ObjectMeta: metav1.ObjectMeta{
-					Name:      "123",
-					Namespace: "ns",
-				},
-				Spec: validPodSpec(&core.Affinity{
-					NodeAffinity: &core.NodeAffinity{
-						RequiredDuringSchedulingIgnoredDuringExecution: &core.NodeSelector{
-							NodeSelectorTerms: []core.NodeSelectorTerm{
-								{
-									MatchExpressions: []core.NodeSelectorRequirement{},
-								},
-							},
-						},
-					},
-				}),
-			},
-		},
 		"invalid weight in preferredDuringSchedulingIgnoredDuringExecution in pod affinity annotations, weight should be in range 1-100": {
 			expectedError: "must be in the range 1-100",
 			spec: core.Pod{