Zero value in nullable and required field

[ShouheiNishi]

The field of the go structure corresponding to the nullable and required OpenAPI property has zero value. In this case, if there is no 'nullable-type' option, the field is encoded as JSON null. But, if 'nullable-type' option is exist, the field is encoded with the zero value of the type parameter of the Nullable generics. Is this difference in behavior intentional?

Test code is https://github.com/ShouheiNishi/oapi-codegen/tree/43adbaa45458d20038d0af271a47802d8c4b5578/internal/test/issues/nullable-zero-value.

$ git status
HEAD detached at 43adbaa
nothing to commit, working tree clean
$ (cd internal/test ; go generate ./issues/nullable-zero-value/... ; go test ./issues/nullable-zero-value/...)
?       github.com/deepmap/oapi-codegen/v2/internal/test/issues/nullable-zero-value/new-nullable        [no test files]
?       github.com/deepmap/oapi-codegen/v2/internal/test/issues/nullable-zero-value/old-nullable        [no test files]
--- FAIL: TestIssue1236 (0.00s)
    issue_test.go:22:
                Error Trace:    /home/nishi/free5gc-deb/free5gc/lib/oapi-codegen/internal/test/issues/nullable-zero-value/issue_test.go:22
                Error:          Not equal:
                                expected: map[string]interface {}{"NullableRequired":interface {}(nil)}
                                actual  : map[string]interface {}{"NullableRequired":0}

                                Diff:
                                --- Expected
                                +++ Actual
                                @@ -1,3 +1,3 @@
                                 (map[string]interface {}) (len=1) {
                                - (string) (len=16) "NullableRequired": (interface {}) <nil>
                                + (string) (len=16) "NullableRequired": (float64) 0
                                 }
                Test:           TestIssue1236
FAIL
FAIL    github.com/deepmap/oapi-codegen/v2/internal/test/issues/nullable-zero-value     0.007s
FAIL
$

[jamietanna]

Hey, so this is something @sonasingh46 and I looked at while introducing the https://github.com/oapi-codegen/nullable type - a required field should always be present, so the correct zero value is the zero value of the type, rather than it being a null

[ShouheiNishi]

Presumably, in the case of nullable and required properties, JSON null is more likely to satisfy the schema than zero value. Therefore, wouldn't it be better if JSON null was output?

[jamietanna]

cc @sonasingh46 thoughts?