fix: boxed oneof field

[xxchan]

fix #1159

Signed-off-by: xxchan [email protected]

[caspermeijn]

I think this test will pass without the other changes. CodeGenerator already makes the OneOf field a Box<T> if self.boxed() == true on line 667.

Can you explain why the other changes are needed?

[caspermeijn]

I don't see where this variable is used. Can you explain what this does?

[xxchan]

I remember I see some unknown attribute error while developing, so I copied the code from message.rs.
https://github.com/xxchan/prost/blob/56b96023a17a0b15026fedc63ec9a5ea8b128ddf/prost-derive/src/field/message.rs#L26-L27

But you are right, this seems to a unnecessary mistake.

[xxchan]

Hi @caspermeijn, thanks for the prompt review! Reverted unnecessary changes, and made CI Green.

I think this test will pass without the other changes.

I'm not sure what you mean by "other changes" here.

But anyway, here's how it works:

As mentioned in #1159, the type for the oneof field was correct. What was wrong is the generated merge function.

I noticed there are #[prost(boxed)] on normal messages fields, but not on the oneof field. After adding it, it works.

pub struct Foo {
    #[prost(message, optional, boxed, tag = "1")]
    pub bar: ::core::option::Option<::prost::alloc::boxed::Box<Bar>>,
    #[prost(oneof = "foo::OneofField", tags = "2, 3")]
    pub oneof_field: ::core::option::Option<foo::OneofField>,
}
/// Nested message and enum types in `Foo`.
    pub mod foo {
        pub enum OneofField {
            #[prost(string, tag = "2")]
            Baz(::prost::alloc::string::String),
// This PR added "boxed" here 
            #[prost(message, boxed, tag = "3")]  
            BoxQux(::prost::alloc::boxed::Box<super::Bar>),
        }
	}

[xxchan]

I remember I see some unknown attribute error while developing, so I copied the code from message.rs.
https://github.com/xxchan/prost/blob/56b96023a17a0b15026fedc63ec9a5ea8b128ddf/prost-derive/src/field/message.rs#L26-L27

But you are right, this seems to a unnecessary mistake.