code-generation.md

Code Generation

To make gRPC requests the client requires generated code for the method definitions and message classes that are defined in .proto files.

protoc is the google protobuf code generation tool. It can generate the JavaScript message classes and also supports using plugins for additional code generation.

ts-protoc-gen is a package that can generate the .d.ts files that declare the contents of the protoc-generated JavaScript files. ts-protoc-gen can also generate @improbable-eng/grpc-web client service/method definitions with the protoc-gen-ts plugin and service=true argument.

This is an example of a complete invokation of protoc with ts-protoc-gen assuming your .proto files are in a directory named my-protos within the current working directory:

protoc \
--plugin=protoc-gen-ts=./node_modules/.bin/protoc-gen-ts \
--js_out=import_style=commonjs,binary:my-generated-code \
--ts_out=service=grpc-web:my-generated-code \
-I ./my-protos \
my-protos/*.proto

A proto file such as book_service.proto:

syntax = "proto3";

package examplecom.library;

message Book {
 int64 isbn = 1;
 string title = 2;
 string author = 3;
}

message GetBookRequest {
 int64 isbn = 1;
}

service BookService {
 rpc GetBook(GetBookRequest) returns (Book) {}
}

Will generate book_service_pb.js, book_service_pb.d.ts, book_service_pb_service.js and book_service_pb_service.d.ts

The first two files contain the message classes while the lst two contain a BookService.GetBook class that acts as method definition that can be used with @improbable-eng/grpc-web.