Ameba
Code style linter for Crystal
(a single-celled animal that catches food and moves about by extending fingerlike projections of protoplasm)
## About
Ameba is a tool for enforcing a consistent Crystal code style, for catching code smells and wrong code constructions.
Ameba's [rules](src/ameba/rules/) traverse AST and report bad parts of your code.
## Installation
### As a project dependency:
Add this to your application's `shard.yml`:
```yaml
development_dependencies:
ameba:
github: veelenga/ameba
```
Build `bin/ameba` binary within your project directory while running `crystal deps`.
You may want also use it on [Travis](travis-ci.org):
```yaml
language: crystal
install:
- crystal deps
script:
- crystal spec
- bin/ameba
```
### OS X
```sh
$ brew tap veelenga/tap
$ brew install ameba
```
### From sources
```sh
$ git clone https://github.com/veelenga/ameba && cd ameba
$ make install
```
## Usage
Run `ameba` binary within your project directory to catch code issues:
```sh
$ ameba
Inspecting 52 files.
.........................F.......F........F.........
src/ameba/ast/traverse.cr:27:5
PredicateName: Favour method name 'node?' over 'is_node?'
src/ameba/rules/empty_expression.cr:42:7
LiteralInCondition: Literal value found in conditional
src/ameba/rules/empty_expression.cr:30:7
UnlessElse: Favour if over unless with else
Finished in 10.53 milliseconds
52 inspected, 3 failures.
```
## Configuration
It is possible to configure or even disable specific rules using YAML configuration file.
By default Ameba is looking for `.ameba.yml` in a project root directory.
Copy and adjust [existed example](config/ameba.yml).
## Write a new Rule
Adding a new rule is as simple as inheriting from `Rule::Base` struct and implementing
your logic to detect a problem:
```crystal
struct DebuggerStatement < Rule::Base
# This is a required method to be implemented by the rule.
# Source will be passed here. If rule finds an issue in this source,
# it reports an error:
#
# source.error rule, line_number, message
#
def test(source)
# This line deletegates verification to a particular AST visitor.
AST::Visitor.new self, source
end
# This method is called once the visitor finds a required node.
def test(source, node : Crystal::Call)
# It reports an error, if there is `debugger` method call
# without arguments and a receiver. That's it, somebody forgot
# to remove a debugger statement.
return unless node.name == "debugger" && node.args.empty? && node.obj.nil?
source.error self, node.location,
"Possible forgotten debugger statement detected"
end
end
```
## Contributors
- [veelenga](https://github.com/veelenga) Vitalii Elenhaupt - creator, maintainer