Add an option to wrap primitives to Option[] about scalapb HOT 8 CLOSED

Two options:

Option A:

int64 deleted_at = 5 [(scalapb.field).type = "Option[org.joda.time.DateTime]"];

and define a TypeMapper[Int, Option[org.joda.time.DateTime]] that maps 0 to None.

Option B:

you can define:

message NullableTime {
  int64 timestamp = 1
}

message Event {
  bytes data = 1;
  NullableTime deleted_at = 5 [(scalapb.field).type = "org.joda.time.DateTime"];
}

Message fields are always in options, and you can then use a custom type for it.

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I like NullableTime idea, thanks. It totally covers my case.

from scalapb.

@thesamet What's the reasoning behind not using Option for optional types in messages? Is it something related to how protobuf messages are encoded (e.g., they can't convey absent values)?

from scalapb.

Exactly. The receiving end has no way of telling if an int32 field was assigned to zero or whether it has not been assigned. See note here: https://developers.google.com/protocol-buffers/docs/proto3?hl=en#default

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@thesamet this seems like a pretty big regression compared to proto2, am I missing something? :)

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@thesamet it looks like proto3 betas will include built-in nullable primitives: protocolbuffers/protobuf#159 (comment).

Could we map these to Option types in the generated code?

That being said, I can't find any trace of them in the repo yet.

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Found them: https://github.com/google/protobuf/blob/master/src/google/protobuf/wrappers.proto

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Trying to use these built-in wrapped types results in compile-time errors:

[error] /Users/zack.angelo/git/galaxy/interfaces/target/scala-2.11/src_managed/main/compiled_protobuf/com/bigcommerce/services/catalog/Product.scala:37: value serializedSize is not a member of com.google.protobuf.Int32Value

[error]       if (id.isDefined) { __size += 1 + com.google.protobuf.CodedOutputStream.computeRawVarint32Size(id.get.serializedSize) + id.get.serializedSize }

Any idea how to fix?

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