Code style linter for Crystal
(a single-celled animal that catches food and moves about by extending fingerlike projections of protoplasm)
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 constructions.
See also Roadmap.
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 `s`
> return s += issues.size
^
src/ameba/formatter/base_formatter.cr:16:7 [Correctable]
[C] Style/RedundantReturn: Redundant `return` detected
> return s += issues.size
^---------------------^
Finished in 389.45 milliseconds
107 inspected, 3 failures
๐ฌ Watch the LuckyCast showing how to use Ameba
Rules that are marked as [Correctable]
in the output can be automatically corrected using --fix
flag:
$ ameba --fix
Ameba allows you to dig deeper into an issue, by showing you details about the issue and the reasoning by it being reported.
To be convenient, you can just copy-paste the PATH:line:column
string from the
report and paste 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
Some quick benchmark results measured while running Ameba on Crystal repo:
$ CRYSTAL_WORKERS=1 ameba #=> 29.11 seconds
$ CRYSTAL_WORKERS=2 ameba #=> 19.49 seconds
$ CRYSTAL_WORKERS=4 ameba #=> 13.48 seconds
$ CRYSTAL_WORKERS=8 ameba #=> 10.14 seconds
Add this to your application's shard.yml
:
development_dependencies:
ameba:
github: crystal-ameba/ameba
version: ~> 1.4.0
Build bin/ameba
binary within your project directory while running shards install
.
$ brew tap crystal-ameba/ameba
$ brew install ameba
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
$ git clone https://github.com/crystal-ameba/ameba && cd ameba
$ make install
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
.
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 !lib)
, meaning it includes all project files with*.cr
extension except those which exist inlib
folder.Excluded
section - an array of wildcards (or paths) to exclude from the source list defined byGlobs
. Defaults to an empty array.
In this example we define default globs and exclude src/compiler
folder:
Globs:
- "**/*.cr"
- "!lib"
Excluded:
- src/compiler
Specific sources can be excluded at rule level:
Style/RedundantBegin:
Excluded:
- src/server/processor.cr
- src/server/api.cr
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
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
- Vim: vim-crystal, Ale
- Emacs: ameba.el
- Sublime Text: Sublime Linter Ameba
- VSCode: vscode-crystal-ameba
- Codacy: codacy-ameba
- GitHub Actions: github-action