ameba

This README is the one indexed from the repository at its latest ref, not from the tag for this version.

• About
• Usage
  • Watch a tutorial
  • Autocorrection
  • Explain issues
  • Describe rules
• Installation
  • As a project dependency
  • Homebrew
  • Docker
  • From sources
• Configuration
  • Sources
  • Rules
  • Inline disabling
• Editors & integrations
• Credits & inspirations
• Contributors

About

Ameba is a static code analysis tool for the Crystal language. It enforces a consistent Crystal code style, also catches code smells and wrong code constructs.

See also Roadmap.

Usage

Run ameba binary within your project directory to catch code issues:

$ ameba
Inspecting 107 files

...............F.....................FF....................................................................

src/ameba/formatter/flycheck_formatter.cr:6:37
[W] Lint/UnusedArgument: Unused argument `location`. If it's necessary, use `_` as an argument name to indicate that it won't be used.
> source.issues.each do |issue, location|
                                ^------^

src/ameba/formatter/base_formatter.cr:16:14
[W] Lint/UselessAssign: Useless assignment to variable `size`
> return size += issues.size
         ^--^

src/ameba/formatter/base_formatter.cr:16:7 [Correctable]
[C] Style/RedundantReturn: Redundant `return` detected
> return size += issues.size
  ^------------------------^

Finished in 389.45 milliseconds
107 inspected, 3 failures

Watch a tutorial

🎬 Watch the LuckyCast showing how to use Ameba

Autocorrection

Rules that are marked as [Correctable] in the output can be automatically corrected using --fix flag:

$ ameba --fix

Explain issues

Ameba allows you to dig deeper into an issue, by showing you details about the issue and the reasoning behind it being reported.

For convenience, you can just copy-paste the PATH:line:column string from the report and paste it behind the ameba command to check it out.

$ ameba crystal/command/format.cr:26:83           # show explanation for the issue
$ ameba --explain crystal/command/format.cr:26:83 # same thing

Describe rules

You can use --describe flag to get a detailed description of a rule:

$ ameba --describe Lint/UselessAssign

Installation

As a project dependency

Add this to your application's shard.yml:

development_dependencies:
  ameba:
    github: crystal-ameba/ameba

To prioritize runtime performance over compilation time, you can add ameba target to the shard.yml file:

targets:
  ameba:
    main: lib/ameba/bin/ameba.cr

And then run:

$ shards build ameba

Alternatively, skip adding ameba target and use crystal build command directly:

$ crystal build -o bin/ameba lib/ameba/bin/ameba.cr

Both of these will result in a compiled binary placed under bin/ameba path.

You can also just run the lib/ameba/bin/ameba.cr file, compiling it on the fly, which is the slowest option:

$ lib/ameba/bin/ameba.cr

Homebrew

$ brew tap crystal-ameba/ameba
$ brew install ameba

Docker

Build the image:

$ docker build -t ghcr.io/crystal-ameba/ameba .

To use the resulting image on a local source folder, mount the current (or target) directory into /src:

$ docker run -v $(pwd):/src ghcr.io/crystal-ameba/ameba

Also available on GitHub: https://github.com/crystal-ameba/ameba/pkgs/container/ameba

From sources

$ git clone https://github.com/crystal-ameba/ameba && cd ameba
$ make install

Configuration

Default configuration file is .ameba.yml. It allows to configure rule properties, disable specific rules and exclude sources from the rules.

Generate new file by running ameba --gen-config.

Sources

List of sources to run Ameba on can be configured globally via:

• Globs section - an array of wildcards (or paths) to include to the inspection. Defaults to %w[**/*.cr **/*.ecr], meaning it includes all project files with *.cr and *.ecr extensions.
• Excluded section - an array of wildcards (or paths) to exclude from the source list defined by Globs. Defaults to %w[lib], meaning it excludes the lib folder.

In this example we define default globs and exclude lib and src/compiler folders:

Globs:
  - "**/*.cr"
  - "**/*.ecr"

Excluded:
  - lib
  - src/compiler

Specific sources can be excluded at rule level:

Style/RedundantBegin:
  Excluded:
    - src/server/processor.cr
    - src/server/api.cr

Rules

One or more rules, or a one or more group of rules can be included or excluded via command line arguments:

$ ameba --only   Lint/Syntax # runs only Lint/Syntax rule
$ ameba --only   Style,Lint  # runs only rules from Style and Lint groups
$ ameba --except Lint/Syntax # runs all rules except Lint/Syntax
$ ameba --except Style,Lint  # runs all rules except rules in Style and Lint groups

Or through the configuration file:

Style/RedundantBegin:
  Enabled: false

Inline disabling

One or more rules or one or more group of rules can be disabled using inline directives:

# ameba:disable Style/LargeNumbers
time = Time.epoch(1483859302)

time = Time.epoch(1483859302) # ameba:disable Style/LargeNumbers, Lint/UselessAssign
time = Time.epoch(1483859302) # ameba:disable Style, Lint

Editors & integrations

• Ameba Language Server: ameba-ls
• Vim: vim-crystal, Ale
• Emacs: ameba.el
• Sublime Text: Sublime Linter Ameba
• VS Code: vscode-crystal-ameba
• Zed (via Ameba LS): Crystal — Zed extension
• Codacy: codacy-ameba
• GitHub Actions: github-action

Credits & inspirations

• Crystal Language
• Rubocop
• Credo
• Dogma

Contributors

• veelenga Vitalii Elenhaupt - creator, maintainer
• Sija Sijawusz Pur Rahnama - contributor, maintainer