Code generation—Tutorial

The Buf CLI's buf generate command generates code from your Protobuf files. It uses a buf.gen.yaml configuration file to configure input, plugin, and output options, and is a direct replacement for code generation in protoc. It can accept many input types—for this tutorial, you'll use a module, which is Buf's key working unit.

The tutorial will take you through various ways to set up your generation, from fully local to managed mode.

Prerequisites

This tutorial assumes you already have Protocol Buffers installed.

• Install the Buf CLI
• Install the protoc-gen-go plugin, or have the corresponding protoc plugin for your output language of choice installed and in your $PATH. The code examples use the Go plugin.

  $ go install google.golang.org/protobuf/cmd/protoc-gen-go@v1.31.0
  $ export PATH="$PATH:$(go env GOPATH)/bin"
  
• Have at least 1 directory containing .proto files

1. Define a module

Modules represent a collection of files that are configured, built, and versioned as a logical unit when performing buf operations. Define a module by adding a buf.yaml config file to the directory of the .proto files you want to group together.

$ cd /path/to/your/directory
$ buf mod init

For example:

.
└── acme
    └── weather
        └── v1
            ├── buf.yaml
            └── weather.proto

buf mod init creates a basic boilerplate buf.yaml file with all of the required elements:

version: v1
breaking:
  use:
    - FILE
lint:
  use:
    - DEFAULT

This new module is your input for the buf generate commands in the rest of the tutorial.

2. Configure your buf.gen.yaml file

To generate code with the Buf CLI, you use a buf.gen.yaml configuration file to specify the languages you want to output, the plugins you want to use, and so on. This file replaces the various command-line flags that are required by protoc.

Create a new buf.gen.yaml file one directory above your .proto files, and copy/paste the following code into it.

.
├── buf.gen.yaml
└── acme
    └── weather
        └── v1
            ├── buf.yaml
            └── weather.proto

version: v1
plugins:
  - plugin: go
    out: gen/go
    opt: paths=source_relative

3. Generate code using local plugins

Now that your configuration is set up, all you need to do is run the command:

$ buf generate

You should see a new gen directory appear in your tree, containing the generated client code. The file structure under the gen directory corresponds to the structure of your Protobuf files:

.
├── buf.gen.yaml
├── acme
│   └── weather
│       └── v1
│           ├── buf.yaml
│           └── weather.proto
└── gen
    ├── go
    └── acme
        └── weather
            └── v1
                └── weather.pb.go

Any errors are printed out in a file:line:column:message format by default. For example:

acme/pet/v1/pet.proto:5:8:acme/payment/v1alpha1/payment.proto: does not exist

4. Generate code using remote plugins

Now you'll regenerate the code, this time using the same plugin hosted on the Buf Schema Registry (BSR).

First, go to the directory where the buf.gen.yaml file is and remove the gen directory.

$ rm -rf gen

Then modify your buf.gen.yaml file to point the plugin: fields to the remote plugin. Note that you can specify the version (and revision number, if one exists).

version: v1
plugins:
  - plugin: buf.build/protocolbuffers/go:v1.31.0
    out: gen/go

Regenerate the code:

$ buf generate

The gen directory reappears with the same structure and files as before. You've now removed the necessity for locally-installed protoc plugins for this set of .proto files.

4. Generate code using managed mode

Managed mode is Buf's way of clearly separating API producer concerns from consumer concerns, and reducing toil and error across organizations:

• Producers are free to publish clean API definitions without including Protobuf options like language-specific package and class prefixes in their .proto files.
• Consumers can enable managed mode with two lines of code and generate code with thoughtful default settings for these options, while still having the flexibility to override them if needed. There's no need to remember or share text files of arcane invocation flags.

Because your project may not include these Protobuf options, we'll use the files below to demonstrate the concept.

syntax = "proto3";

package acme.weather.v1;

// Messages, enums, service, etc.

version: v1
managed:
  enabled: true
  go_package_prefix:
    default: github.com/acme/weather/gen/proto/go
plugins:
  - plugin: buf.build/protocolbuffers/go:v1.31.0
    out: gen/go

When you run buf generate with this setup, the compiler applies the managed mode defaults and the specified go_package_prefix on the fly, creating an invisible .proto file that includes the options you would have had to hard-code:

syntax = "proto3";

package acme.weather.v1;

option go_package = "github.com/acme/weather/gen/proto/go/acme/weather/v1;weatherv1​"

// Messages, enums, service, etc.

and generates the Go code in the specified structure:

.
├── buf.gen.yaml
├── acme
│   └── weather
│       └── v1
│           ├── buf.yaml
│           └── weather.proto
└── gen
    └── go
        └── github.com
            └── acme
                └── weather
                    └── gen
                        └── proto
                            └── go
                                └── acme
                                    └── v1
                                        └── weather.pb.go

Related docs

• See detailed usage examples in the overview
• Learn how to find and consume remote plugins
• Browse the buf generate command reference