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@connectrpc/protoc-gen-connect-es

The code generator for Connect, a simple library to work with servers and clients in ECMAScript with the type-safety of TypeScript. It generates code that is compatible with browsers and Node.js.

Learn more about Connect at github.com/connectrpc/connect-es.

Installation

protoc-gen-connect-es is a code generator plugin for Protocol Buffer compilers, like buf and protoc. It generates clients as well as server definitions from your Protocol Buffer schema, and works in tandem with @bufbuild/protoc-gen-es, the code generator plugin for all Protocol Buffer base types. The code these two plugins generate requires the runtime libraries @connectrpc/connect, and @bufbuild/protobuf.

To install buf, the plugins and their runtime libraries, run:

npm install --save-dev @bufbuild/buf @bufbuild/protoc-gen-es @connectrpc/protoc-gen-connect-es
npm install @connectrpc/connect @bufbuild/protobuf

If you want to call Connect or gRPC-web services from a web browsers, make sure to install @connectrpc/connect-web. If you want servers too, install @connectrpc/connect-node, @connectrpc/connect-fastify, or @connectrpc/connect-express

We use peer dependencies to ensure that code generator and runtime library are compatible with each other. Note that npm installs them automatically, but yarn and pnpm do not.

Generating code

With buf

Add a new configuration file buf.gen.yaml:

# buf.gen.yaml defines a local generation template.
# For details, see https://docs.buf.build/configuration/v1/buf-gen-yaml
version: v1
plugins:
  # This will invoke protoc-gen-es and write output to src/gen
  - plugin: es
    out: src/gen
    opt: target=ts
  # This will invoke protoc-gen-connect-es
  - plugin: connect-es
    out: src/gen
    opt:
      # Add more plugin options here
      - target=ts

To generate code for all protobuf files within your project, simply run:

npx buf generate

Note that buf can generate from various inputs, not just local protobuf files. For example, npx buf generate buf.build/connectrpc/eliza generates code for the module connectrpc/eliza on the Buf Schema Registry.

With protoc

PATH=$PATH:$(pwd)/node_modules/.bin \
  protoc -I . \
  --es_out src/gen \
  --es_opt target=ts \
  --connect-es_out src/gen \
  --connect-es_opt target=ts \
  a.proto b.proto c.proto

Note that we are adding node_modules/.bin to the $PATH, so that the protocol buffer compiler can find them. This happens automatically with npm scripts.

Since yarn v2 and above does not use a node_modules directory, you need to change the variable a bit:

PATH=$(dirname $(yarn bin protoc-gen-es)):$(dirname $(yarn bin protoc-gen-connect-es)):$PATH

Plugin options

target

This option controls whether the plugin generates JavaScript, TypeScript, or TypeScript declaration files.

Possible values:

  • target=js - generates a _connect.js file for every .proto input file.
  • target=ts - generates a _connect.ts file for every .proto input file.
  • target=dts - generates a _connect.d.ts file for every .proto input file.

Multiple values can be given by separating them with +, for example target=js+dts.

By default, we generate JavaScript and TypeScript declaration files, which produces the smallest code size and is the most compatible with various bundler configurations. If you prefer to generate TypeScript, use target=ts.

import_extension=.js

By default, protoc-gen-connect-es (and all other plugins based on @bufbuild/protoplugin) uses a .js file extensions in import paths, even in TypeScript files.

This is unintuitive, but necessary for ECMAScript modules in Node.js. Unfortunately, not all bundlers and tools have caught up yet, and Deno requires .ts. With this plugin option, you can replace .js extensions in import paths with the given value. For example, set

  • import_extension=none to remove the .js extension
  • import_extension=.ts to replace the .js extension with .ts

js_import_style

By default, protoc-gen-connect-es (and all other plugins based on @bufbuild/protoplugin) generate ECMAScript import and export statements. For use cases where CommonJS is difficult to avoid, this option can be used to generate CommonJS require() calls.

Possible values:

  • js_import_style=module generate ECMAScript import / export statements - the default behavior.
  • js_import_style=legacy_commonjs generate CommonJS require() calls.

keep_empty_files=true

By default, protoc-gen-connect-es (and all other plugins based on @bufbuild/protoplugin) omit empty files from the plugin output. This option disables pruning of empty files, to allow for smooth interoperation with Bazel and similar tooling that requires all output files to be declared ahead of time. Unless you use Bazel, it is very unlikely that you need this option.

ts_nocheck=false

By default, protoc-gen-connect-es (and all other plugins based on @bufbuild/protoplugin) generate an annotation at the top of each file: // @ts-nocheck.

We generate the annotation to support a wide range of compiler configurations and future changes to the language. But there can be situations where the annotation shadows an underlying problem, for example an unresolvable import. To remove the annotation and to enable type checks, set the plugin option ts_nocheck=false.

Example generated code

eliza.proto

syntax = "proto3";

package connectrpc.eliza.v1;

// ElizaService provides a way to talk to Eliza, a port of the DOCTOR script
// for Joseph Weizenbaum's original ELIZA program. Created in the mid-1960s at
// the MIT Artificial Intelligence Laboratory, ELIZA demonstrates the
// superficiality of human-computer communication. DOCTOR simulates a
// psychotherapist, and is commonly found as an Easter egg in emacs
// distributions.
service ElizaService {
  // Say is a unary RPC. Eliza responds to the prompt with a single sentence.
  rpc Say(SayRequest) returns (SayResponse) {}
}

// SayRequest is a single-sentence request.
message SayRequest {
  string sentence = 1;
}

// SayRequest is a single-sentence response.
message SayResponse {
  string sentence = 1;
}

eliza_connect.ts

/**
 * ElizaService provides a way to talk to Eliza, a port of the DOCTOR script
 * for Joseph Weizenbaum's original ELIZA program. Created in the mid-1960s at
 * the MIT Artificial Intelligence Laboratory, ELIZA demonstrates the
 * superficiality of human-computer communication. DOCTOR simulates a
 * psychotherapist, and is commonly found as an Easter egg in emacs
 * distributions.
 *
 * @generated from service connectrpc.eliza.v1.ElizaService
 */
export const ElizaService = {
  typeName: "connectrpc.eliza.v1.ElizaService",
  methods: {
    /**
     * Say is a unary RPC. Eliza responds to the prompt with a single sentence.
     *
     * @generated from rpc connectrpc.eliza.v1.ElizaService.Say
     */
    say: {
      name: "Say",
      I: SayRequest,
      O: SayResponse,
      kind: MethodKind.Unary,
    },
  }
} as const;