ameba-custom-rules

# Ameba Custom Rules

Create custom linting rules for Ameba to enforce project-specific code quality standards and catch domain-specific code smells in Crystal projects.

## Understanding Custom Rules

Custom Ameba rules allow you to:

- Enforce project-specific coding standards
- Catch domain-specific anti-patterns
- Validate business logic constraints
- Ensure consistency across large codebases
- Create reusable rule libraries for your organization
- Extend Ameba's built-in capabilities

## Rule Anatomy

### Basic Rule Structure

Every Ameba rule inherits from `Ameba::Rule::Base` and follows this structure:

```crystal
module Ameba::Rule::Custom
  # Rule that enforces documentation on public classes
  class DocumentedClasses < Base
    properties do
      description "Enforces public classes to be documented"
    end

    MSG = "Class must be documented with a comment"

    def test(source)
      AST::NodeVisitor.new self, source
    end

    def test(source, node : Crystal::ClassDef)
      return unless node.visibility.public?

      doc = node.doc
      issue_for(node, MSG) if doc.nil? || doc.empty?
    end
  end
end
```

### Key Components

1. **Module namespace** - Custom rules typically use `Ameba::Rule::Custom` or `Ameba::Rule::<Category>`
2. **Base class** - All rules inherit from `Ameba::Rule::Base`
3. **Properties block** - Defines rule metadata and configuration
4. **Message constant** - The error message shown to users
5. **Test method** - Entry point that initializes the AST visitor
6. **Overloaded test methods** - Handle specific AST node types

## Creating Your First Custom Rule

### Step 1: Project Setup

Create a Crystal library for your custom rules:

```bash
# Initialize a new Crystal library
crystal init lib ameba-custom-rules
cd ameba-custom-rules
```

Update `shard.yml`:

```yaml
name: ameba-custom-rules
version: 0.1.0
authors:
  - Your Name <your.email@example.com>

description: Custom Ameba rules for your project

crystal: ">= 1.0.0"

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