Code quality threshold checking as part of your build
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Fails your build if code quality thresholds are not met.

Discipline will set you free.


gem install cane
cane --abc-glob '{lib,spec}/**/*.rb' --abc-max 15

Your main build task should run this, probably via bundle exec. It will have a non-zero exit code if any quality checks fail. Also, a report:

> cane

Methods exceeded maximum allowed ABC complexity (2):

  lib/cane.rb  Cane > sample    23
  lib/cane.rb  Cane > sample_2  17

Lines violated style requirements (2):

  lib/cane.rb:20   Line length >80
  lib/cane.rb:42   Trailing whitespace

Classes are not documented (1):
  lib/cane:3  SomeClass

Customize behaviour with a wealth of options:

> cane --help
Usage: cane [options]

You can also put these options in a .cane file.

        --abc-glob GLOB              Glob to run ABC metrics over (default: {app,lib}/**/*.rb)
        --abc-max VALUE              Ignore methods under this complexity (default: 15)
        --no-abc                     Disable ABC checking

        --style-glob GLOB            Glob to run style metrics over (default: {app,lib,spec}/**/*.rb)
        --style-measure VALUE        Max line length (default: 80)
        --no-style                   Disable style checking

        --doc-glob GLOB              Glob to run documentation checks over (default: {app,lib}/**/*.rb)
        --no-doc                     Disable documentation checking

        --gte FILE,THRESHOLD         If FILE contains a number, verify it is >= to THRESHOLD.

        --max-violations VALUE       Max allowed violations (default: 0)
        --exclusions-file FILE       YAML file containing a list of exclusions

    -v, --version                    Show version
    -h, --help                       Show this message

Set default options into a .cane file:

> cat .cane
--abc-glob **/*.rb
> cane

It works just like this:

> cane --no-doc --abc-glob '**/*.rb'

Integrating with Rake

  require 'cane/rake_task'

  desc "Run cane to check quality metrics" do |cane|
    cane.abc_max = 10
    cane.add_threshold 'coverage/covered_percent', :>=, 99
    cane.no_style = true

  task :default => :quality
rescue LoadError
  warn "cane not available, quality task not provided."

Rescuing LoadError is a good idea, since rake -T failing is totally frustrating.

Adding to a legacy project

Cane can be configured to still pass in the presence of a set number of violations using the --max-violations option. This is ideal for retrofitting on to an existing application that may already have many violations. By setting the maximum to the current number, no immediate changes will be required to your existing code base, but you will be protected from things getting worse.

You can also consider defining exclusions for each violation (see below).

Integrating with SimpleCov

Any value in a file can be used as a threshold:

> echo "89" > coverage/covered_percent
> cane --gte 'coverage/covered_percent,90'

Quality threshold crossed

  coverage/covered_percent is 89, should be >= 90

You can use a SimpleCov formatter to create the required file:

class SimpleCov::Formatter::QualityFormatter
  def format(result)"coverage/covered_percent", "w") do |f|
      f.puts result.source_files.covered_percent.to_f

SimpleCov.formatter = SimpleCov::Formatter::QualityFormatter

Defining Exclusions

Occasionally, you may want to permanently ignore specific cane violations. Create a YAML file like so:

  - Some::Fully::Qualified::Class.some_class_method
  - Some::Fully::Qualified::Class#some_instance_method

Tell cane about this file using the --exclusions-file option:

> cane --exclusions-file path/to/exclusions.yml

Currently, only the abc and style checks support exclusions.


Requires MRI 1.9, since it depends on the ripper library to calculate complexity metrics. This only applies to the Ruby used to run Cane, not the project it is being run against. In other words, you can run Cane against your 1.8 project.


Ask questions on Stack Overflow. We keep an eye on new cane questions.


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