protolint

README

protolint

protolint is a command line tool which lints Protocol Buffer files (proto3):

• Runs fast because this works without compiler.
• Easy to follow the official style guide. The rules and the style guide correspond to each other exactly.
• Allow to disable rules with a comment in a Protocol Buffer file.
  • It is useful for projects which must keep API compatibility while enforce the style guide as much as possible.
• Undergone testing for all rules.

Installation

go get -u -v github.com/yoheimuta/protolint/cmd/pl

Usage

pl lint example.proto example2.proto # file mode, specify multiple specific files
pl lint .                            # directory mode, search for all .proto files recursively
pl .                                 # same as "pl lint ."
pl lint -config_dir_path=path/to .   # search path/to for .protolint.yaml
pl lint -fix .                       # automatically fix some of the problems reported by some rules
pl list                              # list all current lint rules being used

Rules

See internal/addon/rules in detail.

The rule set follows:

• Official Style Guide. This is enabled by default.
• Formatting Style Guide. This is enabled by default.
  • Enforce a maximum line length. The length of a line is defined as the number of Unicode characters in the line. You can configure the detail with .protolint.yaml.
  • Enforce a consistent indentation style. The --fix option on the command line can automatically fix some of the problems reported by this rule. The default style is 4 spaces. You can configure the detail with .protolint.yaml.

ID	Purpose
ENUM_FIELD_NAMES_UPPER_SNAKE_CASE	Verifies that all enum field names are CAPITALS_WITH_UNDERSCORES.
ENUM_NAMES_UPPER_CAMEL_CASE	Verifies that all enum names are CamelCase (with an initial capital).
FIELD_NAMES_LOWER_SNAKE_CASE	Verifies that all field names are underscore_separated_names.
MESSAGE_NAMES_UPPER_CAMEL_CASE	Verifies that all message names are CamelCase (with an initial capital).
RPC_NAMES_UPPER_CAMEL_CASE	Verifies that all rpc names are CamelCase (with an initial capital).
SERVICE_NAMES_UPPER_CAMEL_CASE	Verifies that all service names are CamelCase (with an initial capital).
MAX_LINE_LENGTH	Enforces a maximum line length.
INDENT	Enforces a consistent indentation style.

- is a bad style, + is a good style:

ENUM_FIELD_NAMES_UPPER_SNAKE_CASE

enum Foo {
-  firstValue = 0;
+  FIRST_VALUE = 0;
-  second_value = 1;
+  SECOND_VALUE = 1;
}

ENUM_NAMES_UPPER_CAMEL_CASE

- enum foobar {
+ enum FooBar {
  FIRST_VALUE = 0;
  SECOND_VALUE = 1;
}

FIELD_NAMES_LOWER_SNAKE_CASE

message SongServerRequest {
-  required string SongName = 1;
+  required string song_name = 1;
}

MESSAGE_NAMES_UPPER_CAMEL_CASE

- message song_server_request {
+ message SongServerRequest {
  required string SongName = 1;
  required string song_name = 1;
}

RPC_NAMES_UPPER_CAMEL_CASE

service FooService {
-  rpc get_something(FooRequest) returns (FooResponse);
+  rpc GetSomething(FooRequest) returns (FooResponse);
}

RPC_NAMES_UPPER_CAMEL_CASE

- service foo_service {
+ service FooService {
  rpc get_something(FooRequest) returns (FooResponse);
  rpc GetSomething(FooRequest) returns (FooResponse);
}

Configuring

Disable rules in a Protocol Buffer file

Rules can be disabled with a comment inside a Protocol Buffer file with the following format. The rules will be disabled until the end of the file or until the linter sees a matching enable comment:

// protolint:disable <ruleID1> [<ruleID2> <ruleID3>...]
...
// protolint:enable <ruleID1> [<ruleID2> <ruleID3>...]

It's also possible to modify a disable command by appending :next or :this for only applying the command to this(current) or the next line respectively.

For example:

enum Foo {
  // protolint:disable:next ENUM_FIELD_NAMES_UPPER_SNAKE_CASE
  firstValue = 0;    // no error
  second_value = 1;  // protolint:disable:this ENUM_FIELD_NAMES_UPPER_SNAKE_CASE
  THIRD_VALUE = 2;   // spits out an error
}

Config file

protolint can operate using a config file named .protolint.yaml.

Refer to _example/config/.protolint.yaml for the config file specification.

protolint will search a current working directory for the config file by default. And it can search the specified directory with -config_dir_path flag.

Motivation

There exists the similar protobuf linters as of 2018-12-20.

One is a plug-in for Google's Protocol Buffers compiler.

• When you just want to lint the files, it may be tedious to create the compilation environment.
• And it generally takes a lot of time to compile the files than to parse the files.

Other is a command line tool which also lints Protocol Buffer files.

• While it has a lot of features other than lint, it seems cumbersome for users who just want the linter.
• The lint rule slants towards to be opinionated.
• Further more, the rule set and the official style guide don't correspond to each other exactly. It requires to understand both rules and the guide in detail, and then to combine the rules accurately.

Dependencies

• go-protoparser

Acknowledgement

Thank you to the prototool package: https://github.com/uber/prototool

I referred to the package for the good proven design, interface and some source code.