Re: [protobuf] Enum values and proto3 Any types

[Josh Humphries]

That totally works. I don't actually need anything at the moment. But I was
looking at the spec and implementing some stuff around it -- like for
downloading and resolving type schemas from type URLs -- and noticed it as
an omission. The main omission is that nothing describes the contents of
google.protobuf.Field#type_url when the field's kind is enum. If it is an
encoded google.protobuf.Enum (which is the only thing that really makes
sense), it would be nice to state so in the spec. It might also be nice to
clearly call out in the doc for google.protobuf.Any that scalar types must
be boxed via wrappers (and enum types must be boxed via custom message
types).

FWIW, a generic wrapper type for an enum is certainly possible and would
look something like this:

message EnumValue {
  // The URL, optionally omitted scheme, for the enumeration type.
  type_url string
  valueint32
}

Unfortunately, EnumValue is a name conflict with the existing type that
describes an element in the enumeration. Maybe WrappedEnumValue?



*Josh Humphries*
jh...@bluegosling.com

On Mon, Apr 17, 2017 at 12:54 PM, Adam Cozzette 
wrote:

> I think the right solution for putting an enum or primitive type in an Any
> field would be to use a wrapper type like you mentioned. Since there's no
> real way to create a generic wrapper for all enums, you would probably need
> to create a specific wrapper for each enum you want to store in an Any
> field. Does that work for your situation?
>
> On Thu, Apr 13, 2017 at 7:31 PM, Josh Humphries 
> wrote:
>
>> I have a question about Any types in proto3. I'm guessing they aren't
>> quite fully-fleshed out since I haven't found a lot in the way of doc or
>> real support in the Java and Go implementations.
>>
>> My question: can you use enums or scalar types as values of an Any field?
>> If so, how do they look?
>>
>> For scalar types, I can understand if the answer is to use the wrapper
>> well-known types instead. *But* there doesn't appear to be a wrapper for
>> enum values. There is a well-known type named google.protobuf.EnumValue,
>> however it is part of the "schema description" well-known types and doesn't
>> carry enough data for wrapping an enum value (mainly, it's missing a
>> reference to its enum type, e.g. a type URL).
>>
>> It would be nice if the Any message's type_url field could be a URL that
>> returned an enum description, not just a message description. But the docs
>> state that the contents at that URL are an encoded google.protobuf.Type,
>> which describes a message and does not support enum types. Should it
>> instead have a single one-of field that can be an enum or message
>> description?
>>
>> Similarly, the type_url field for google.protobuf.Field is in a similar
>> conundrum. The doc states it is *"t**he field type URL, without the
>> scheme, for message or enumeration types"*, but nothing really talks
>> about enumeration types. The naive assumption is that the URL contents are
>> an enum description (e.g. an encoded google.protobuf.Enum). But if
>> that's the case, I could try to put an enum type into an Any field and
>> indicate that same URL. I then get into trouble because I'd be looking to
>> parse a google.protobuf.Type, in order to understand the Any message
>> contents, but actually get back the bytes for a google.protobuf.Enum.
>>
>> That doesn't seem sound.
>>
>> 
>> *Josh Humphries*
>> jh...@bluegosling.com
>>
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>
>

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Re: [protobuf] Enum values and proto3 Any types

['Adam Cozzette' via Protocol Buffers]

I think the right solution for putting an enum or primitive type in an Any
field would be to use a wrapper type like you mentioned. Since there's no
real way to create a generic wrapper for all enums, you would probably need
to create a specific wrapper for each enum you want to store in an Any
field. Does that work for your situation?

On Thu, Apr 13, 2017 at 7:31 PM, Josh Humphries 
wrote:

> I have a question about Any types in proto3. I'm guessing they aren't
> quite fully-fleshed out since I haven't found a lot in the way of doc or
> real support in the Java and Go implementations.
>
> My question: can you use enums or scalar types as values of an Any field?
> If so, how do they look?
>
> For scalar types, I can understand if the answer is to use the wrapper
> well-known types instead. *But* there doesn't appear to be a wrapper for
> enum values. There is a well-known type named google.protobuf.EnumValue,
> however it is part of the "schema description" well-known types and doesn't
> carry enough data for wrapping an enum value (mainly, it's missing a
> reference to its enum type, e.g. a type URL).
>
> It would be nice if the Any message's type_url field could be a URL that
> returned an enum description, not just a message description. But the docs
> state that the contents at that URL are an encoded google.protobuf.Type,
> which describes a message and does not support enum types. Should it
> instead have a single one-of field that can be an enum or message
> description?
>
> Similarly, the type_url field for google.protobuf.Field is in a similar
> conundrum. The doc states it is *"t**he field type URL, without the
> scheme, for message or enumeration types"*, but nothing really talks
> about enumeration types. The naive assumption is that the URL contents are
> an enum description (e.g. an encoded google.protobuf.Enum). But if that's
> the case, I could try to put an enum type into an Any field and indicate
> that same URL. I then get into trouble because I'd be looking to parse a
> google.protobuf.Type, in order to understand the Any message contents,
> but actually get back the bytes for a google.protobuf.Enum.
>
> That doesn't seem sound.
>
> 
> *Josh Humphries*
> jh...@bluegosling.com
>
> --
> You received this message because you are subscribed to the Google Groups
> "Protocol Buffers" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to protobuf+unsubscr...@googlegroups.com.
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> Visit this group at https://groups.google.com/group/protobuf.
> For more options, visit https://groups.google.com/d/optout.
>

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[protobuf] Enum values and proto3 Any types

[Josh Humphries]

I have a question about Any types in proto3. I'm guessing they aren't quite
fully-fleshed out since I haven't found a lot in the way of doc or real
support in the Java and Go implementations.

My question: can you use enums or scalar types as values of an Any field?
If so, how do they look?

For scalar types, I can understand if the answer is to use the wrapper
well-known types instead. *But* there doesn't appear to be a wrapper for
enum values. There is a well-known type named google.protobuf.EnumValue,
however it is part of the "schema description" well-known types and doesn't
carry enough data for wrapping an enum value (mainly, it's missing a
reference to its enum type, e.g. a type URL).

It would be nice if the Any message's type_url field could be a URL that
returned an enum description, not just a message description. But the docs
state that the contents at that URL are an encoded google.protobuf.Type,
which describes a message and does not support enum types. Should it
instead have a single one-of field that can be an enum or message
description?

Similarly, the type_url field for google.protobuf.Field is in a similar
conundrum. The doc states it is *"t**he field type URL, without the scheme,
for message or enumeration types"*, but nothing really talks about
enumeration types. The naive assumption is that the URL contents are an
enum description (e.g. an encoded google.protobuf.Enum). But if that's the
case, I could try to put an enum type into an Any field and indicate that
same URL. I then get into trouble because I'd be looking to parse a
google.protobuf.Type, in order to understand the Any message contents, but
actually get back the bytes for a google.protobuf.Enum.

That doesn't seem sound.


*Josh Humphries*
jh...@bluegosling.com

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