protoc-gen-prost-serde

A protoc plugin that generates serde serialization implementations that follow the conventions of protobuf-JSON.

When used in projects that use only Rust code, the preferred mechanism for generating protobuf definitions with Prost! is to use prost-build from within a build.rs file and then generate serde implementations using pbjson-build. However, when working in polyglot environments, it can be advantageous to utilize common tooling in the Protocol Buffers ecosystem. One common tool used for this purpose is buf, which simplifies the code generation process and includes several useful features, including linting, package management, and breaking change detection.

Usage

Ensure that protoc-gen-prost-serde has been installed within a directory on your $PATH. Then invoke protoc from the command line as follows:

protoc --prost-serde_out=proto/gen -I proto proto/greeter/v1/greeter.proto

Options

This tool supports all the same options from pbjson-build. For more information on the effects of these settings, see the related documentation from that crate:

• btree_map=<proto_path>: btree_map
• default_package_filename=<value>: default_package_filename
• extern_path=<proto_path>=<rust_path>: extern_path
• retain_enum_prefix(=<boolean>): retain_enum_prefix
• preserve_proto_field_names=(<boolean>): preserve_proto_field_names
• ignore_unknown_fields=(<boolean>): ignore_unknown_fields
• emit_fields=(<boolean>): emit_fields
• use_integers_for_enums=(<boolean>): use_integers_for_enums

In addition, the following options can also be specified:

• no_include(=<boolean>): Skips adding an include into the file generated by protoc-gen-prost. This behavior may be desired if this plugin is run in a separate protoc invocation and you encounter a Tried to insert into file that doesn't exist error.

A note on parameter values:

• <proto_path>: Protobuf paths beginning with . will be matched from the global root (prefix matches). All other paths will be matched as suffix matches.
• (=<boolean>): Boolean values may be specified after a parameter, but if not, the value is assumed to be true by virtue of having listed the parameter.

Usage with protoc and protoc-gen-prost

To make it easier to work with the base definitions generated by prost, this plugin assumes that it is being run in a chained mode in the same protoc invocation as protoc-gen-prost. This can be done by specifying multiple plugins in the same protoc invocation like so:

protoc -I proto proto/greeter/v1/greeter.proto \
    --prost_out=proto/gen \
    --prost_opt=compile_well_known_types \
    --prost_opt=extern_path=.google.protobuf=::pbjson_types \
    --prost-serde_out=proto/gen

When running as separate invocations, protoc won't be aware of the base definitions that were generated by protoc-gen-prost. In this case, using the no_include directive is necessary, and you will need to separately include the generated .serde.rs file.

protoc -I proto proto/greeter/v1/greeter.proto \
    --prost_out=proto/gen \
    --prost_opt=compile_well_known_types \
    --prost_opt=extern_path=.google.protobuf=::pbjson_types

protoc -I proto proto/greeter/v1/greeter.proto \
    --prost-serde_out=proto/gen \
    --prost-serde_opt=no_include

Usage with buf

When used with buf, options can be specified in the buf.gen.yaml file. protoc-gen-prost-serde should appear as a plugin step after any protoc-gen-prost steps. In addition, the compile_well_known_types and extern_path=.google.protobuf=::pbjson_types options should be specified.

version: v1
plugins:
  - plugin: prost
    out: gen
    opt:
      - compile_well_known_types
      - extern_path=.google.protobuf=::pbjson_types
  - plugin: prost-serde
    out: gen

The protoc-gen-prost-serde plugin is also published on the Buf Schema Registry as a plugin which you can execute remotely, without needing to explicitly install this tool. See the plugin listing to identify the latest published version for use. The plugin is referenced as follows:

version: v1
plugins:
  - plugin: buf.build/community/neoeinstein-prost-serde:v0.2.3
    out: gen

protoc-gen-prost-serde is also compatible with the protoc-gen-prost-crate plugin:

version: v1
plugins:
  - plugin: prost
    out: gen
    opt:
      - compile_well_known_types
      - extern_path=.google.protobuf=::pbjson_types
  - plugin: prost-serde
    out: gen
  - plugin: prost-crate
    strategy: all
    out: gen
    opt:
      - no_features