Document 0 as a special case in RV comparison

staging/src/k8s.io/apimachinery/pkg/util/resourceversion/resourceversion.go

@@ -40,6 +40,8 @@ func (i InvalidResourceVersion) Error() string {
 // The function will return an error if the resource version is not a properly
 // formatted positive integer, but has no restriction on length. A properly
 // formatted integer will not contain leading zeros or non integer characters.
+// Zero is also considered an invalid value as it is used as a special value in
+// list/watch events and will never be a live resource version.
 func CompareResourceVersion(a, b string) (int, error) {
 	if !isWellFormed(a) {
 		return 0, InvalidResourceVersion{rv: a}

staging/src/k8s.io/apimachinery/pkg/util/resourceversion/resourceversion_test.go

@@ -34,12 +34,36 @@ func TestCompareResourceVersion(t *testing.T) {
 			b:        "200",
 			expected: -1,
 		},
+		{
+			name: "a is zero, invalid",
+			a:    "0",
+			b:    "1",
+			err:  true,
+		},
+		{
+			name: "both zero",
+			a:    "0",
+			b:    "0",
+			err:  true,
+		},
 		{
 			name:     "a greater than b",
 			a:        "200",
 			b:        "100",
 			expected: 1,
 		},
+		{
+			name: "b is 0, invalid",
+			a:    "1",
+			b:    "0",
+			err:  true,
+		},
+		{
+			name:     "a equal to b small",
+			a:        "1",
+			b:        "1",
+			expected: 0,
+		},
 		{
 			name:     "a equal to b",
 			a:        "100",

test/e2e/common/apimachinery/resourceversion_matchers.go

@@ -57,6 +57,10 @@ func (m *HaveValidResourceVersionMatcher) Match(actual interface{}) (success boo
 		m.failureReason = fmt.Sprintf("resource version requires %d bits (more than 128)", val.BitLen())
 		return false, nil
 	}
+	if val.Cmp(big.NewInt(0)) == 0 {
+		m.failureReason = "the resource version is zero which is not valid"
+		return false, nil
+	}
 
 	return true, nil
 }

test/e2e/common/apimachinery/resourceversion_matchers_test.go

@@ -38,7 +38,8 @@ func TestHaveValidResourceVersionMatch(t *testing.T) {
 		{
 			name:            "zero resource version",
 			resourceVersion: "0",
-			expectedMatch:   true,
+			expectedMatch:   false,
+			expectedFailure: "Expected resource version to be a valid uint128, but got \"0\": the resource version is zero which is not valid",
 		},
 		{
 			name:            "negative resource version",