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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 single-module workspace.

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

Prerequisites

We recommend completing the Buf CLI tour to get an overview of the Buf CLI first.

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"

1. Define a module

Modules represent a collection of files that are configured, built, and versioned as a logical unit when performing Buf operations. Workspaces are collections of modules and are configured by the buf.yaml configuration file, which should generally be put above the directories that contain the modules within it.

For example, a buf-codegeneration-tutorial workspace with a single module would be structured like this (this workspace will be the example throughout):

buf-codegeneration-tutorial
├── buf.yaml
└── proto
    └── acme
        └── weather
            └── v1
                └── weather.proto

Create a basic boilerplate buf.yaml file with all of the required elements by running buf config init in your workspace root:

$ mkdir buf-codegeneration-tutorial
$ cd buf-codegeneration-tutorial
$ buf config init

The command generates a minimal configuration file to define your module:

Default buf.yaml config file
# For details on buf.yaml configuration, visit https://buf.build/docs/configuration/v2/buf-yaml
version: v2
lint:
  use:
    - STANDARD
breaking:
  use:
    - FILE

Next, add the module paths for the Protobuf file directories within the workspace (one per module):

buf.yaml
# For details on buf.yaml configuration, visit https://buf.build/docs/configuration/v2/buf-yaml
version: v2
+modules:
+  - path: proto
lint:
  use:
    - STANDARD
breaking:
  use:
    - FILE

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

Note

For more information about the specific fields, see the buf.yaml reference.

2. Add proto files to your module

Add a weather.proto file within the module's path:

Create a weather.proto file
$ mkdir -p proto/acme/weather/v1
$ touch proto/acme/weather/v1/weather.proto

Copy and paste this content into that file:

proto/acme/weather/v1/weather.proto
syntax = "proto3";

package acme.weather.v1;

option go_package = "acme/weather/v1";

enum Condition {
  CONDITION_UNSPECIFIED = 0;
  CONDITION_SUNNY = 1;
  CONDITION_RAINY = 2;
}

message GetWeatherRequest {
  float latitude = 1;
  float longitude = 2;
}

message GetWeatherResponse {
  float temperature = 1;
  Condition condition = 2;
}

service WeatherService {
  rpc GetWeather (GetWeatherRequest) returns (GetWeatherResponse);
}

3. 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 in the workspace root, and copy/paste the following code into it.

buf-codegeneration-tutorial
├── buf.gen.yaml
├── buf.yaml
└── proto
    └── acme
        └── weather
            └── v1
                └── weather.proto
buf.gen.yaml
version: v2
clean: true
plugins:
  - local: protoc-gen-go
    out: gen/go
    opt: paths=source_relative
inputs:
  - directory: proto

The file defines which plugins to use to generate code, where to output it, what the inputs are. It uses clean to state that we'd like to delete all previously generated code each time we run buf generate. For more information about the available fields, see the buf.gen.yaml reference.

Note

buf generate can take many types of input beyond a local directory. See the inputs reference for details about how to specify other types of input to Buf CLI commands.

4. Generate code using local plugins

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

Run from workspace root
$ 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-codegeneration-tutorial
├── buf.gen.yaml
├── buf.yaml
├── gen
│   └── go
│       └── acme
│           └── weather
│               └── v1
│                   └── weather.pb.go
└── proto
    └── acme
        └── weather
            └── v1
                └── weather.proto

5. 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, remove the gen directory.

Run from workspace root
$ rm -rf gen

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

buf.gen.yaml
version: v2
plugins:
- - local: protoc-gen-go
+ - remote: buf.build/protocolbuffers/go:v1.31.0
    out: gen/go
    opt: paths=source_relative

Regenerate the code:

Run from workspace root
$ 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.

Note

See Using remote plugins for more information about the advantages of remote plugins and where to find them.

6. 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. Given the requirement that the go_package file option needs to be prepended with github.com/acme/weather/gen/go, add the corresponding managed mode settings to your buf.gen.yaml:

buf.gen.yaml with managed mode settings for go_package
version: v2
clean: true
+managed:
+  enabled: true
+  override:
+    - file_option: go_package_prefix
+      value: github.com/acme/weather/gen/go
plugins:
  - remote: buf.build/protocolbuffers/go:v1.31.0
    out: gen/go
-   opt: paths=source_relative
inputs:
  - directory: proto

Now, when you run buf generate, the compiler applies the managed mode defaults and the specified go_package_prefix on the fly, creating a temporary .proto file to generate code that includes the options you would have had to hard-code into each of your .proto files:

Temporary (i.e., managed-mode generated) acme/weather/v1/weather.proto
syntax = "proto3";

package acme.weather.v1;

option go_package = "github.com/acme/weather/gen/go/acme/weather/v1"

// Messages, enums, services, etc.

This generates Go code in the specified structure:

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

Note

For more information about managed mode's defaults, usage, and fields, see Managed mode and the buf.gen.yaml reference.