Add embed message field option

[Adphi]

[UPDATED after comments] add embedding support with (go.field).embed.
Example:

message MessageWithEmbeddedFields {
  Embedded message = 1 [(go.field).embed = true];
}

message Embedded {
  string message = 1;
}

[ydnar]

Wow, interesting. Some quick feedback, as I'm on my phone:

• I'd prefer the API to be explicit rather than implicit based on an empty name, e.g.: go.field.embedded = true
• Can you revert the formatting changes in the proto files that aren't relevant to this PR?
• Tests should exist and pass.

Thanks for the PR!

[Adphi]

I agree with you on explicit over implicit (I didn't want to change the defined API).
I added the go.field.embedded option.
I will revert formatting changes.

[Adphi]

@ydnar do you want to explicitly fail on unsupported options annotation, like oneof field annotated as embedded or non message type annotated as embedded or just silently ignore these unsupported options?

[ydnar]

@ydnar do you want to explicitly fail on unsupported options annotation, like oneof field annotated as embedded or non message type annotated as embedded or just silently ignore these unsupported options?

Explicitly fail with a verbose error message.

[Adphi]

@ydnar do you want to explicitly fail on unsupported options annotation, like oneof field annotated as embedded or non message type annotated as embedded or just silently ignore these unsupported options?

Explicitly fail with a verbose error message.

I agree with you, but I can see some limitations based on the existing API...
None of the scan methods returns an error, which does not allow validation of protobuf options, this would lead to an ugly os.Exit(code) inside one of the scan methods, the logger output being redirected to io.Discard by default if PROTO_PATCH_DEBUG_LOGGING is not defined, the log.Fatal message would not reach the user... I think it might be better to address the problem in a separated issue / pull request.

[Adphi]

Ping @ydnar

[ydnar]

Ping @ydnar

Hey there—we’re on vacation for the July 4th weekend. I’ll take a look at the PR next week when we’re back home!

[ydnar]

Hi there, thanks for your patience. I’d love to see this merged with a couple changes.

[Adphi]

Hi @ydnar !
Thanks for your reply. I'll make the requested changes as soon as I can.
FYI: I started to work on the "casttype" implementation 😃

[ydnar]

FYI: I started to work on the "casttype" implementation 😃

Wow, I’m curious to see how that works.

[ydnar]

Additional comments.