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**.
- 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`.
Since the default behavior of `revive` is compatible with `golint`, without providing any additional flags, the only difference you'd notice is faster execution.
-`-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:
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.
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`).
| [`context-as-argument`](./RULES_DESCRIPTIONS.md#context-as-argument) | n/a | `context.Context` should be the first argument of a function. | yes | no |
| [`argument-limit`](./RULES_DESCRIPTIONS.md#argument-limit) | int | Specifies the maximum number of arguments a function can receive | no | no |
| [`cyclomatic`](./RULES_DESCRIPTIONS.md#cyclomatic) | int | Sets restriction for maximum Cyclomatic complexity. | no | no |
| [`max-public-structs`](./RULES_DESCRIPTIONS.md#max-public-structs) | int | The maximum number of public structs in a file. | no | no |
| [`file-header`](./RULES_DESCRIPTIONS.md#file-header) | string | Header which each file should have. | no | no |
| [`empty-block`](./RULES_DESCRIPTIONS.md#empty-block) | n/a | Warns on empty code blocks | no | no |
| [`superfluous-else`](./RULES_DESCRIPTIONS.md#superfluous-else) | n/a | Prevents redundant else statements (extends [`indent-error-flow`](./RULES_DESCRIPTIONS.md#indent-error-flow)) | no | no |
| [`confusing-naming`](./RULES_DESCRIPTIONS.md#confusing-naming) | n/a | Warns on methods with names that differ only by capitalization | no | no |
| [`get-return`](./RULES_DESCRIPTIONS.md#get-return) | n/a | Warns on getters that do not yield any result | no | no |
| [`modifies-parameter`](./RULES_DESCRIPTIONS.md#modifies-parameter) | n/a | Warns on assignments to function parameters | no | no |
| [`confusing-results`](./RULES_DESCRIPTIONS.md#confusing-results) | n/a | Suggests to name potentially confusing function results | no | no |
| [`deep-exit`](./RULES_DESCRIPTIONS.md#deep-exit) | n/a | Looks for program exits in funcs other than `main()` or `init()` | no | no |
| [`unused-parameter`](./RULES_DESCRIPTIONS.md#unused-parameter) | n/a | Suggests to rename or remove unused function parameters | no | no |
| [`unreachable-code`](./RULES_DESCRIPTIONS.md#unreachable-code) | n/a | Warns on unreachable code | no | no |
| [`add-constant`](./RULES_DESCRIPTIONS.md#add-constant) | map | Suggests using constant for magic numbers and string literals | no | no |
| [`flag-parameter`](./RULES_DESCRIPTIONS.md#flag-parameter) | n/a | Warns on boolean parameters that create a control coupling | no | no |
| [`unnecessary-stmt`](./RULES_DESCRIPTIONS.md#unnecessary-stmt) | n/a | Suggests removing or simplifying unnecessary statements | no | no |
| [`struct-tag`](./RULES_DESCRIPTIONS.md#struct-tag) | n/a | Checks common struct tags like `json`,`xml`,`yaml` | no | no |
| [`modifies-value-receiver`](./RULES_DESCRIPTIONS.md#modifies-value-receiver) | n/a | Warns on assignments to value-passed method receivers | no | yes |
| [`constant-logical-expr`](./RULES_DESCRIPTIONS.md#constant-logical-expr) | n/a | Warns on constant logical expressions | no | no |
| [`bool-literal-in-expr`](./RULES_DESCRIPTIONS.md#bool-literal-in-expr)| n/a | Suggests removing Boolean literals from logic expressions | no | no |
| [`redefines-builtin-id`](./RULES_DESCRIPTIONS.md#redefines-builtin-id)| n/a | Warns on redefinitions of builtin identifiers | no | no |
| [`function-result-limit`](./RULES_DESCRIPTIONS.md#function-result-limit) | int | Specifies the maximum number of results a function can return | no | no |
| [`imports-blacklist`](./RULES_DESCRIPTIONS.md#imports-blacklist) | []string | Disallows importing the specified packages | no | no |
| [`range-val-in-closure`](./RULES_DESCRIPTIONS.md#range-val-in-closure)| n/a | Warns if range value is used in a closure dispatched as goroutine| no | no |
| [`waitgroup-by-value`](./RULES_DESCRIPTIONS.md#waitgroup-by-value) | n/a | Warns on functions taking sync.WaitGroup as a by-value parameter | no | no |
| [`atomic`](./RULES_DESCRIPTIONS.md#atomic) | n/a | Check for common mistaken usages of the `sync/atomic` package | no | no |
| [`empty-lines`](./RULES_DESCRIPTIONS.md#empty-lines) | n/a | Warns when there are heading or trailing newlines in a block | no | no |
| [`line-lenght-limit`](./RULES_DESCRIPTIONS.md#line-lenght-limit) | int | Specifies the maximum number of characters in a line | no | no |
Here you can find how you can configure some of the existing rules:
### `var-naming`
This rule accepts two slices of strings, a whitelist and a blacklist of initialisms. By default the rule behaves exactly as the alternative in `golint` but optionally, you can relax it (see [golint/lint/issues/89](https://github.com/golang/lint/issues/89))
```toml
[rule.var-naming]
arguments = [["ID"], ["VM"]]
```
This way, revive will not warn for identifier called `customId` but will warn that `customVm` should be called `customVM`.
**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/).
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:
- 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.
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.
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:
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.
