[ANN] ProtocGen.jl protobuf support for julia

Package Announcements
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ProtocGen.jl

CI

Julia code generator for Protocol Buffers.
It is meant to be used as a protoc plugin.
Passes the official required proto2 and proto3 conformance tests for both binary and JSON.

Install

Install protoc-gen-julia binary:

julia> using Pkg
pkg> app add ProtocGen

Usage

cd examples
mkdir out

protoc --julia_out=out addressbook.proto

where

// addressbook.proto
syntax = "proto3";

package tutorial;

import "google/protobuf/timestamp.proto";

enum PhoneType {
    PHONE_TYPE_UNSPECIFIED = 0;
    PHONE_TYPE_MOBILE = 1;
    PHONE_TYPE_HOME = 2;
    PHONE_TYPE_WORK = 3;
}

message PhoneNumber {
    string number = 1;
    PhoneType type = 2;
}

message Person {
    string name = 1;
    int32 id = 2;
    optional string email = 3;
    repeated PhoneNumber phones = 4;
    google.protobuf.Timestamp last_updated = 5;
}

message AddressBook {
    repeated Person people = 1;
}

This generates out/addressbook_pb.jl. It depends on the
ProtocGen.jl package:

include("out/addressbook_pb.jl")

person = Person(
    name = "Alice",
    id = Int32(42),
    email = "alice@example.com",
    phones = [
        PhoneNumber(number = "+1-555-0100", type = PhoneType.MOBILE),
        PhoneNumber(number = "+1-555-0101", type = PhoneType.WORK),
    ],
    last_updated = google_protobuf.Timestamp(seconds = Int64(1_715_000_000)),
)

# Binary wire format
bytes = encode(person)
@assert decode(bytes, Person) == person

# Canonical protobuf JSON mapping (Timestamp renders as RFC 3339)
js = encode_json(person)
# {"name":"Alice","id":42,"email":"alice@example.com",
#  "phones":[…],"lastUpdated":"2024-05-06T12:53:20Z"}
@assert decode_json(Person, js) == person

Alternatives

ProtoBuf.jl is a good alternative.
It is meant to be used as a julia package, not protoc plugin.

Acknowledgement

The wire codec under src/codec/ is copied with light modifications
from ProtoBuf.jl
(MIT-licensed, © 2022 RelationalAI / Tomáš Drvoštěp / contributors).
ProtoBuf.jl is the long-running Julia Protocol Buffers library; this
package takes a different architectural route (descriptor-driven, with
proto3 optional presence and proto2 required semantics fixed) but
stands on its codec. See LICENSE.md.

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