Defining a static message

[a...@binoklo.com]

Hello,

I'd like to do something like this:

syntax = "proto3";

package foo;

enum ModuleId {

  MODULE_ID_UNKNOWN = 0;

  MODULE_ID_BAR = 1;

  ...
}

message ModuleDetails {

  ModuleId id = 1;

  string name = 2;

  ...

}

message Modules {

  repeated ModuleDetails modules = 1;

}

And then define a static Modules message. This seems better to me than shipping a, for example, yaml configuration file.

It looks like this feature has been suggested and rejected a couple of times. Any suggestions on how I could achieve something like this?

Thanks,

--

Adriano

[Em Rauch]

Unfortunately the .proto syntax doesn't currently have support for defining arbitrary constants in .proto files. There are various ways you can kinda do it, including making a proto2 syntax file and a message where every field has some default value set, and then in your code just using the default instance of that message and reading the fields to observe the 'defaults' (that technique doesn't enable you have config instances of message types defined otherwise though, just primitives). You also can kinda achieve it by making a FileOption, and then set that FileOption on a file with whatever values (which does allow for specifying message types).

More typically the config usecase is satisfied by keeping a config in TextProto format separate from the .proto schema today.

Constants in .proto files is on our radar as a possible future syntax addition, but there's a lot of nuances to it and so its not definite that it will be added at any point.

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