@grpc/proto-loader

What is @grpc/proto-loader?

The @grpc/proto-loader package is used to load .proto files and generate JavaScript objects. It is primarily used in conjunction with gRPC, a high-performance, open-source universal RPC framework, to dynamically load protocol buffer definitions at runtime.

What are @grpc/proto-loader's main functionalities?

Loading .proto files

This feature allows you to load .proto files and create a package definition that can be used to make RPC calls.

const grpc = require('@grpc/grpc-js');
const protoLoader = require('@grpc/proto-loader');
const packageDefinition = protoLoader.loadSync('your_proto_file.proto', {});
const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const yourService = protoDescriptor.your_package.YourService;

Customizing the loader options

This feature allows you to customize how the .proto files are loaded by specifying options such as whether to keep the original field casing or convert enums to strings.

const options = {
  keepCase: true,
  longs: String,
  enums: String,
  defaults: true,
  oneofs: true
};
const packageDefinition = protoLoader.loadSync('your_proto_file.proto', options);

Asynchronous loading of .proto files

This feature allows you to load .proto files asynchronously, which can be useful if you want to handle the loading process without blocking the event loop.

const protoLoader = require('@grpc/proto-loader');
protoLoader.load('your_proto_file.proto', {}).then(packageDefinition => {
  const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
  // Use protoDescriptor to create gRPC service client
}).catch(err => {
  console.error('Error loading .proto file', err);
});

Other packages similar to @grpc/proto-loader

protobufjs

Protobufjs is a pure JavaScript implementation of Protocol Buffers. It provides similar functionality to @grpc/proto-loader but with additional features like creating .proto files programmatically and a more complex API for handling protocol buffers.

grpc-tools

grpc-tools is a package that includes protocol buffer compiler (protoc) and a plugin for generating gRPC service code. It is used for generating static service code from .proto files, as opposed to the dynamic loading approach of @grpc/proto-loader.

grpc-web

grpc-web provides a JavaScript library that lets browser clients access a gRPC service. It is similar to @grpc/proto-loader in that it deals with gRPC and protocol buffers, but it is specifically designed for web clients.

README

gRPC Protobuf Loader

A utility package for loading .proto files for use with gRPC, using the latest Protobuf.js package. Please refer to protobuf.js' documentation to understands its features and limitations.

Installation

npm install @grpc/proto-loader

Usage

const protoLoader = require('@grpc/proto-loader');
const grpcLibrary = require('grpc');
// OR
const grpcLibrary = require('@grpc/grpc-js');

protoLoader.load(protoFileName, options).then(packageDefinition => {
  const packageObject = grpcLibrary.loadPackageDefinition(packageDefinition);
});
// OR
const packageDefinition = protoLoader.loadSync(protoFileName, options);
const packageObject = grpcLibrary.loadPackageDefinition(packageDefinition);

The options parameter is an object that can have the following optional properties:

Field name	Valid values	Description
keepCase	true or false	Preserve field names. The default is to change them to camel case.
longs	String or Number	The type to use to represent long values. Defaults to a Long object type.
enums	String	The type to use to represent enum values. Defaults to the numeric value.
bytes	Array or String	The type to use to represent bytes values. Defaults to Buffer.
defaults	true or false	Set default values on output objects. Defaults to false.
arrays	true or false	Set empty arrays for missing array values even if defaults is false Defaults to false.
objects	true or false	Set empty objects for missing object values even if defaults is false Defaults to false.
oneofs	true or false	Set virtual oneof properties to the present field's name. Defaults to false.
json	true or false	Represent Infinity and NaN as strings in float fields, and automatically decode google.protobuf.Any values. Defaults to false
includeDirs	An array of strings	A list of search paths for imported .proto files.

The following options object closely approximates the existing behavior of grpc.load:

const options = {
  keepCase: true,
  longs: String,
  enums: String,
  defaults: true,
  oneofs: true
}

Generating TypeScript types

The proto-loader-gen-types script distributed with this package can be used to generate TypeScript type information for the objects loaded at runtime. More information about how to use it can be found in the @grpc/proto-loader TypeScript Type Generator CLI Tool proposal document. The arguments mostly match the load function's options; the full usage information is as follows:

proto-loader-gen-types.js [options] filenames...

Options:
      --help             Show help                                     [boolean]
      --version          Show version number                           [boolean]
      --keepCase         Preserve the case of field names
                                                      [boolean] [default: false]
      --longs            The type that should be used to output 64 bit integer
                         values. Can be String, Number[string] [default: "Long"]
      --enums            The type that should be used to output enum fields. Can
                         be String                  [string] [default: "number"]
      --bytes            The type that should be used to output bytes fields.
                         Can be String, Array       [string] [default: "Buffer"]
      --defaults         Output default values for omitted fields
                                                      [boolean] [default: false]
      --arrays           Output default values for omitted repeated fields even
                         if --defaults is not set     [boolean] [default: false]
      --objects          Output default values for omitted message fields even
                         if --defaults is not set     [boolean] [default: false]
      --oneofs           Output virtual oneof fields set to the present field's
                         name                         [boolean] [default: false]
      --json             Represent Infinity and NaN as strings in float fields.
                         Also decode google.protobuf.Any automatically
                                                      [boolean] [default: false]
      --includeComments  Generate doc comments from comments in the original
                         files                        [boolean] [default: false]
  -I, --includeDirs      Directories to search for included files        [array]
  -O, --outDir           Directory in which to output files  [string] [required]
      --grpcLib          The gRPC implementation library that these types will
                         be used with                        [string] [required]
      --inputTemplate    Template for mapping input or "permissive" type names
                                                        [string] [default: "%s"]
      --outputTemplate   Template for mapping output or "restricted" type names
                                                [string] [default: "%s__Output"]
      --inputBranded     Output property for branded type for  "permissive"
                         types with fullName of the Message as its value
                                                      [boolean] [default: false]
      --outputBranded    Output property for branded type for  "restricted"
                         types with fullName of the Message as its value
                                                      [boolean] [default: false]

Example Usage

Generate the types:

$(npm bin)/proto-loader-gen-types --longs=String --enums=String --defaults --oneofs --grpcLib=@grpc/grpc-js --outDir=proto/ proto/*.proto

Consume the types:

import * as grpc from '@grpc/grpc-js';
import * as protoLoader from '@grpc/proto-loader';
import { ProtoGrpcType } from './proto/example';
import { ExampleHandlers } from './proto/example_package/Example';

const exampleServer: ExampleHandlers = {
  // server handlers implementation...
};

const packageDefinition = protoLoader.loadSync('./proto/example.proto');
const proto = (grpc.loadPackageDefinition(
  packageDefinition
) as unknown) as ProtoGrpcType;

const server = new grpc.Server();
server.addService(proto.example_package.Example.service, exampleServer);