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

Readme

Source

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`.
`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
}

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Last updated on 10 Jul 2020

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