[![Build Status](https://travis-ci.org/mgechev/revive.svg?branch=master)](https://travis-ci.org/mgechev/revive) # revive Fast, configurable, extensible, flexible, and beautiful linter for Go. Drop-in replacement of golint. **`Revive` provides a framework for development of custom rules, and lets you define a strict preset for enhancing your development & code review processes**.


Logo by Georgi Serev

Here's how `revive` is different from `golint`: - Allows us to enable or disable rules using a configuration file. - Allows us to configure the linting rules with a TOML file. - 2x faster running the same rules as golint. - Provides functionality for disabling a specific rule or the entire linter for a file or a range of lines. - `golint` allows this only for generated files. - Optional type checking. Most rules in golint do not require type checking. If you disable them in the config file, revive will run over 6x faster than golint. - Provides multiple formatters which let us customize the output. - Allows us to customize the return code for the entire linter or based on the failure of only some rules. - _Everyone can extend it easily with custom rules or formatters._ - `Revive` provides more rules compared to `golint`.

- [revive](#revive) - [Usage](#usage) - [Text Editors](#text-editors) - [Installation](#installation) - [Command Line Flags](#command-line-flags) - [Sample Invocations](#sample-invocations) - [Comment Annotations](#comment-annotations) - [Configuration](#configuration) - [Default Configuration](#default-configuration) - [Recommended Configuration](#recommended-configuration) - [Available Rules](#available-rules) - [Available Formatters](#available-formatters) - [Friendly](#friendly) - [Stylish](#stylish) - [Default](#default) - [Extensibility](#extensibility) - [Custom Rule](#custom-rule) - [Example](#example) - [Custom Formatter](#custom-formatter) - [Speed Comparison](#speed-comparison) - [golint](#golint) - [revive](#revive-1) - [Contributors](#contributors) - [License](#license) ## Usage Since the default behavior of `revive` is compatible with `golint`, without providing any additional flags, the only difference you'd notice is faster execution. ### Text Editors - Support for VSCode in [vscode-go](https://github.com/Microsoft/vscode-go/pull/1699). - Support for vim via [w0rp/ale](https://github.com/w0rp/ale): ```vim call ale#linter#Define('go', { \ 'name': 'revive', \ 'output_stream': 'both', \ 'executable': 'revive', \ 'read_buffer': 0, \ 'command': 'revive %t', \ 'callback': 'ale#handlers#unix#HandleAsWarning', \}) ``` ### Installation ```bash go get -u github.com/mgechev/revive ``` ### Command Line Flags `revive` accepts three command line parameters: - `-config [PATH]` - path to config file in TOML format. - `-exclude [PATTERN]` - pattern for files/directories/packages to be excluded for linting. You can specify the files you want to exclude for linting either as package name (i.e. `github.com/mgechev/revive`), list them as individual files (i.e. `file.go`), directories (i.e. `./foo/...`), or any combination of the three. - `-formatter [NAME]` - formatter to be used for the output. The currently available formatters are: - `default` - will output the failures the same way that `golint` does. - `json` - outputs the failures in JSON format. - `friendly` - outputs the failures when found. Shows summary of all the failures. - `stylish` - formats the failures in a table. Keep in mind that it doesn't stream the output so it might be perceived as slower compared to others. ### Sample Invocations ```shell revive -config revive.toml -exclude file1.go -exclude file2.go -formatter friendly github.com/mgechev/revive package/... ``` - The command above will use the configuration from `revive.toml` - `revive` will ignore `file1.go` and `file2.go` - The output will be formatted with the `friendly` formatter - The linter will analyze `github.com/mgechev/revive` and the files in `package` ### Comment Annotations Using comments, you can disable the linter for the entire file or only range of lines: ```go //revive:disable func Public() {} //revive:enable ``` The snippet above, will disable `revive` between the `revive:disable` and `revive:enable` comments. If you skip `revive:enable`, the linter will be disabled for the rest of the file. You can do the same on a rule level. In case you want to disable only a particular rule, you can use: ```go //revive:disable:unexported-return func Public() private { return private } //revive:enable:unexported-return ``` This way, `revive` will not warn you for that you're returning an object of an unexported type, from an exported function. ### Configuration `revive` can be configured with a TOML file. Here's a sample configuration with explanation for the individual properties: ```toml # When set to false, ignores files with "GENERATED" header, similar to golint ignoreGeneratedHeader = true # Sets the default severity to "warning" severity = "warning" # Sets the default failure confidence. This means that linting errors # with less than 0.8 confidence will be ignored. confidence = 0.8 # Sets the error code for failures with severity "error" errorCode = 0 # Sets the error code for failures with severity "warning" warningCode = 0 # Configuration of the `cyclomatic` rule. Here we specify that # the rule should fail if it detects code with higher complexity than 10. [rule.cyclomatic] arguments = [10] # Sets the severity of the `package-comments` rule to "error". [rule.package-comments] severity = "error" ``` ### Default Configuration The default configuration of `revive` can be found at `defaults.toml`. This will enable all rules available in `golint` and use their default configuration (i.e. the way they are hardcoded in `golint`). ```shell revive -config defaults.toml github.com/mgechev/revive ``` This will use the configuration file `defaults.toml`, the `default` formatter, and will run linting over the `github.com/mgechev/revive` package. ### Recommended Configuration ```shell revive -config config.toml -formatter friendly github.com/mgechev/revive ``` This will use `config.toml`, the `friendly` formatter, and will run linting over the `github.com/mgechev/revive` package. ## Available Rules List of all available rules. The rules ported from `golint` are left unchanged and indicated in the `golint` column. | Name | Config | Description | `golint` | Typed | | --------------------- | :----: | :--------------------------------------------------------------- | :------: | :---: | | `context-keys-type` | n/a | Disallows the usage of basic types in `context.WithValue`. | yes | yes | | `time-naming` | n/a | Conventions around the naming of time variables. | yes | yes | | `var-declaration` | n/a | Reduces redundancies around variable declaration. | yes | yes | | `unexported-return` | n/a | Warns when a public return is from unexported type. | yes | yes | | `errorf` | n/a | Should replace `error.New(fmt.Sprintf())` with `error.Errorf()` | yes | yes | | `blank-imports` | n/a | Disallows blank imports | yes | no | | `context-as-argument` | n/a | `context.Context` should be the first argument of a function. | yes | no | | `dot-imports` | n/a | Forbids `.` imports. | yes | no | | `error-return` | n/a | The error return parameter should be last. | yes | no | | `error-strings` | n/a | Conventions around error strings. | yes | no | | `error-naming` | n/a | Naming of error variables. | yes | no | | `exported` | n/a | Naming and commenting conventions on exported symbols. | yes | no | | `if-return` | n/a | Redundant if when returning an error. | yes | no | | `increment-decrement` | n/a | Use `i++` and `i--` instead of `i += 1` and `i -= 1`. | yes | no | | `var-naming` | n/a | Naming rules. | yes | no | | `package-comments` | n/a | Package commenting conventions. | yes | no | | `range` | n/a | Prevents redundant variables when iterating over a collection. | yes | no | | `receiver-naming` | n/a | Conventions around the naming of receivers. | yes | no | | `indent-error-flow` | n/a | Prevents redundant else statements. | yes | no | | `argument-limit` | int | Specifies the maximum number of arguments a function can receive | no | no | | `cyclomatic` | int | Sets restriction for maximum Cyclomatic complexity. | no | no | | `max-public-structs` | int | The maximum number of public structs in a file. | no | no | | `file-header` | string | Header which each file should have. | no | no | | `empty-block` | n/a | Warns on empty code blocks | no | no | | `superfluous-else` | n/a | Prevents redundant else statements (extends `indent-error-flow`) | no | no | | `confusing-naming` | n/a | Warns on methods with names that differ only by capitalization | no | no | | `get-return` | n/a | Warns on getters that do not yield any result | no | no | | `modifies-param` | n/a | Warns on assignments to function parameters | no | no | | `confusing-results` | n/a | Suggests to name potentially confusing function results | no | no | | `deep-exit` | n/a | Looks for program exits in funcs other than `main()` or `init()` | no | no | | `unused-parameter` | n/a | Suggests to rename or remove unused function parameters | no | no | ## Available Formatters This section lists all the available formatters and provides a screenshot for each one. ### Friendly ![Friendly formatter](/assets/friendly-formatter.png) ### Stylish ![Stylish formatter](/assets/stylish-formatter.png) ### Default ![Default formatter](/assets/default-formatter.png) ## Extensibility The tool can be extended with custom rules or formatters. This section contains additional information on how to implement such. **To extend the linter with a custom rule or a formatter you'll have to push it to this repository or fork it**. This is due to the limited `-buildmode=plugin` support which [works only on Linux (with known issues)](https://golang.org/pkg/plugin/). ### Custom Rule Each rule needs to implement the `lint.Rule` interface: ```go type Rule interface { Name() string Apply(*File, Arguments) []Failure } ``` The `Arguments` type is an alias of the type `[]interface{}`. The arguments of the rule are passed from the configuration file. #### Example Let's suppose we have developed a rule called `BanStructNameRule` which disallow us to name a structure with given identifier. We can set the banned identifier by using the TOML configuration file: ```toml [rule.ban-struct-name] arguments = ["Foo"] ``` With the snippet above we: - Enable the rule with name `ban-struct-name`. The `Name()` method of our rule should return a string which matches `ban-struct-name`. - Configure the rule with the argument `Foo`. The list of arguments will be passed to `Apply(*File, Arguments)` together with the target file we're linting currently. A sample rule implementation can be found [here](/rule/argument-limit.go). ### Custom Formatter Each formatter needs to implement the following interface: ```go type Formatter interface { Format(<-chan Failure, RulesConfig) (string, error) Name() string } ``` The `Format` method accepts a channel of `Failure` instances and the configuration of the enabled rules. The `Name()` method should return a string different from the names of the already existing rules. This string is used when specifying the formatter when invoking the `revive` CLI tool. For a sample formatter, take a look at [this file](/formatter/json.go). ## Speed Comparison Compared to `golint`, `revive` performs better because it lints the files for each individual rule into a separate goroutine. Here's a basic performance benchmark on MacBook Pro Early 2013 run on kubernetes: ### golint ```shell time golint kubernetes/... > /dev/null real 0m54.837s user 0m57.844s sys 0m9.146s ``` ### revive ```shell # no type checking time revive -config untyped.toml kubernetes/... > /dev/null real 0m8.471s user 0m40.721s sys 0m3.262s ``` Keep in mind that if you use rules which require type checking, the performance may drop to 2x faster than `golint`: ```shell # type checking enabled time revive kubernetes/... > /dev/null real 0m26.211s user 2m6.708s sys 0m17.192s ``` Currently, type checking is enabled by default. If you want to run the linter without type checking, remove all typed rules from the configuration file. ## Contributors | [mgechev](https://github.com/mgechev) | [chavacava](https://github.com/chavacava) | [tamird](https://github.com/tamird) | [paul-at-start](https://github.com/paul-at-start) | [vkrol](https://github.com/vkrol) | | :---------------------------------------------------------------------------------------------------------------------------: | :---------------------------------------------------------------------------------------------------------------------------------: | :--------------------------------------------------------------------------------------------------------------------------: | :----------------------------------------------------------------------------------------------------------------------------------------: | :-----------------------------------------------------------------------------------------------------------------------: | | [mgechev](https://github.com/mgechev) | [chavacava](https://github.com/chavacava) | [tamird](https://github.com/tamird) | [paul-at-start](https://github.com/paul-at-start) | [vkrol](https://github.com/vkrol) | ## License MIT