Recently, I had the chance to work on the proto files for one of my projects to define the contract for a service. Since this was a brand-new service, I had to set it up from scratch and learned how to write and format the proto files using best practices.

What is proto? read more about protocol bufferes

There are different tools available for linting the proto files some of them are

1. protoc-gen-lint
2. prototool
3. buf - we have used the buf as a proto linter. Follow this for installation of buf.

What is buf?

The buf CLI is a tool for working with Protocol Buffers. It has a variety of supported functions such as lint, breaking changes detection, formatter, etc.

Format your protos

To improve readability and have standard formatting enabled across teams, buf provides the auto-formatting on proto files. This enables the files to be formatted correctly and with following the standards.

Use the following command to format your files.

buf format

This will produce any violations in formatting to the console.

To auto-format the files in-place with the difference in file changes, use the below command.

buf format -w --diff

Detect code style checks

*Linter *- A static code analysis used to flag programming errors, bugs, stylistic errors, and suspicious constructs.

For proto files, it’s no different, to verify the new changes adhere to proto standards use the buf linter.

buf lint /path/to/proto/files/

This will produce any errors, warning to console if there are any violations in writing proto files. You can analyze and update the protofiles according to standard rules.

Automatically lint with GitLab CI pipeline

Whenever there is a change in your repository, your CI pipeline will automatically run buf lint to check for any violations.

To check add the below code snippet to the .gitlab-ci.yml

stages:
  - lint

lint:
  stage: lint
  image: 
    name: bufbuild/buf:1.7.0
    entrypoint: [""]
  script:
    - buf lint

buf configuration rules

buf supports three categories of rule configurations.

1. MINIMAL
2. BASIC
3. DEFAULT By default, buf has DEFAULT linting configuration which has below details.

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

Use buf mod init to generate DEFAUTL configuration rules for your project.

You can update this file with different rules as per the requirements.

 version: v1
 lint:
   use:
     - DEFAULT
   except:
     - PACKAGE_VERSION_SUFFIX
     - FIELD_LOWER_SNAKE_CASE
     - SERVICE_SUFFIX
   ignore:
     - google/type/datetime.proto
 breaking:
   use:
     - FILE

Hope this article gave understanding of how to use buf tool for formatting, linting your proto files.
Happy learning!