Merge pull request #43271 from liggitt/affinity-namespace

Automatic merge from submit-queue (batch tested with PRs 43313, 43257, 43271, 43307)

Remove 'all namespaces' meaning of empty list in PodAffinityTerm

Removes the distinction between `null` and `[]` for the PodAffinityTerm#namespaces field (option 4 discussed in https://github.com/kubernetes/kubernetes/issues/43203#issuecomment-287237992), since we can't distinguish between them in protobuf (and it's a less than ideal API)

Leaves the door open to reintroducing "all namespaces" function via a dedicated field or a dedicated token in the list of namespaces

Wanted to get a PR open and tests green in case we went with this option.

Not sure what doc/release-note is needed if the "all namespaces" function is not present in 1.6

pkg/api/types.go

@@ -1886,9 +1886,7 @@ type PodAffinityTerm struct {
 	// +optional
 	LabelSelector *metav1.LabelSelector
 	// namespaces specifies which namespaces the labelSelector applies to (matches against);
-	// nil list means "this pod's namespace," empty list means "all namespaces"
-	// The json tag here is not "omitempty" since we need to distinguish nil and empty.
-	// See https://golang.org/pkg/encoding/json/#Marshal for more details.
+	// null or empty list means "this pod's namespace"
 	Namespaces []string
 	// This pod should be co-located (affinity) or not co-located (anti-affinity) with the pods matching
 	// the labelSelector in the specified namespaces, where co-located is defined as running on a node