Generating openapi from proto gives field of type string and format RFC3339 but not vice versa

[panperla]

I need such output in my proto

...
message XYZ {
    string versionName = 1 [json_name = "versionname"];
    string branchName = 2 [json_name = "branchname"];
    string appName = 3 [json_name = "appname"];
    string appDomainName = 4 [json_name = "appdomainname"];
    string appURL = 5 [json_name = "appurl"];
    string commitSHA = 6 [json_name = "commitsha"];
    google.protobuf.Timestamp responseTime = 7 [json_name = "responsetime"];
}
...

During the conversion from openapi google.protobuf.Timestamp type is being just translated as string.
In openapi I'm defining it as a:

responsetime:
                    type: string
                    format: RFC3339

To conclude generating openapi file from proto gives me field with type string and format RFC3339 but when I convert it back to proto the google.protobufTImestamp is lost.

I might be missing something please point me into right direction how I can arrive with google.protobuf.Timestamp responseTime from openapi.

[adolfo]

I'm having a similar issue, but under a slightly different use case. I'm going from Protobuf to OpenAPI to a Rest Client. In that process I'm losing the timestamp type information and ending up with a plain string as well.

I believe this is caused by an invalid string format in the generated OpenAPI spec. Specifically, the timestamp format "RFC3339" isn't a valid format per the OpenAPI docs. It states that the "date-time" format already conforms to RFC 3339:

OpenAPI defines the following built-in string formats: [...] date-time – the date-time notation as defined by RFC 3339, section 5.6, for example, 2017-07-21T17:32:28Z source1 source2

It appears gnostic is inserting "RFC3339" where "date-time" appears to be the correct format value:

gnostic/cmd/protoc-gen-openapi/generator/openapi-v3.go

Lines 766 to 770 in 3334dd9

	case ".google.protobuf.Timestamp":
	// Timestamps are serialized as strings
	return &v3.SchemaOrReference{
	Oneof: &v3.SchemaOrReference_Schema{
	Schema: &v3.Schema{Type: "string", Format: "RFC3339"}}}

I propose that the "RFC3339" format be replaced with the correct "date-time" format. This will enable other tools such as OpenAPI-Generator, etc. to do the right thing when it comes to generating timestamps for each respective language.

It's not clear if this was an intentional value that is used downstream, or a simple oversight, but I'd gladly open a PR if the maintainers agree with this change. /cc @morphar @timburks

[adolfo]

Addressed in #319