What happened:
As part of adding skew testing for serialized API responses, we discovered a diff in serialized proto responses when roundtripping data from 1.14:

    --- FAIL: TestRoundTripExternalTypes/.v1.Status (0.02s)
        --- FAIL: TestRoundTripExternalTypes/.v1.Status/fixtures-v1.14.0 (0.02s)
            fixtures.go:195: proto data differed from fixture
            fixtures.go:205: fixture vs reserialized:
                  strings.Join({
                  	... // 7 identical lines
                  	`    2: "8551505577692297499"`,
                  	`    3: ""`,
                + 	"    4: 0",
                  	"  }",
                  	"  2 {",
                  	... // 21 identical lines
                  }, "\n")

This is due to the RemainingItemCount field in ListMeta, which is always serialized in proto messages, because it is not a pointer.

What you expected to happen:
Proto messages do not include the optional field when unset.

How to reproduce it (as minimally and precisely as possible):

• Check out Add json/protobuf/yaml fixtures #78309
• Run go test ./vendor/k8s.io/api -run TestRoundTripExternalTypes//1.14 (tests round-tripping serialized API content for all types we shipped in 1.14)

This needs to be resolved before 1.15 ships.

/milestone v1.15
/kind bug
/sig api-machinery
/priority important-soon
/assign @caesarxuchao