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revive/README.md
2018-02-18 22:19:37 -08:00

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# revive
Fast, configurable, extensible, flexible, and beautiful linter for Go.
<p align="center">
<img src="./assets/logo.png" alt="" width="200">
</p>
Here's how `revive` is different from `golint`:
* Allows you to enable or disable rules using a configuration file.
* Allows you to configure the linting rules with a TOML file.
* Provides functionality to disable a specific rule or the entire linter for a file or a range of lines.
* Provides more rules compared to `golint`.
* Provides multiple formatters which let you customize the output.
* Allows you to customize the return code for the entire linter or based on the failure of only some rules.
* Open for addition of new rules or formatters.
* Faster. It runs the rules over each file in a separate goroutine.
## Usage
`Revive` is **configurable** linter which you can fit your needs. By default you can use `revive` with the default configuration options. This way the linter will work the same way `golint` does.
### Command Line Flags
Revive accepts three command line parameters:
* `config` - path to config file in TOML format.
* `exclude` - 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 file2.go`), directories (i.e. `./foo/...`), or any combination of the three.
* `formatter` - formatter to be used for the output. The currently available formatters are:
* `default` - will output the warnings the same way that `golint` does.
* `json` - outputs the warnings in JSON format.
* `cli` - formats the warnings in a table.
### Configuration
Revive can be configured with a TOML file
### 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 cli github.com/mgechev/revive
```
This will use `config.toml`, the `cli` formatter, and will run linting over the `github.com/mgechev/revive` package. Keep in mind that the `cli` formatter performs aggregation and grouping of the discovered problems in your code. This means that the output will be buffered and printed at once. If you want a streaming output use `default`.
## Extension
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**. 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).
## License
MIT