Mago

Magic numbers detector for Ruby source code.

Magic numbers

Magic numbers (unnamed constants) are considered as a bad programming practice. Extracting them into constants or explaining variables usually provides the following advantages:

It is easier to read and understand.
It is easier to alter the value of the number, as it is not duplicated.
It may facilitate parameterization.
It helps to detect typos.

Installation

gem install mago

Usage

Ruby code in square.rb:

P = 3.14

r = 5
square = P * r ** 2

Run:

mago ./square.rb
./square.rb:3 detected magic number 5
./square.rb:4 detected magic number 2

Ignore specific numbers

Use --ignore or -i option to ignore specific numbers. By default 0 and 1 are ignored.

mago -i 2,3 ./square.rb
./square.rb:3 detected magic number 5

Show source code

Use --source or -s option to show line of source code where magic number was found.

mago -s ./square.rb
./square.rb:3| r = 5
./square.rb:4| square = P * r ** 2

Color output

Use --color or -c option to colorize output.

Using API

See complete documentation at rubydoc. Here is a simple example:

require 'mago'

# Initialize detector with ruby files and options
detector = Mago::Detector.new(['./square.rb', './math/fibonacci.rb'], :ignore => [1,2,3])

# Run detector it to build a report
report = detector.run  # => #<Mago::Report ...>

# Use report as you want. The following code provides an output like this:
#  ./square.rb
#      Line 3:  5
#      Line 6:  0
#  ./math/fibonacci.rb
#      Line 1:  0.0
#      Line 6:  5.0
report.files.each do |file|
  puts file.path
  file.magic_numbers.each do |number|
    puts "    Line #{number.line}:  #{number.value}"
  end
end

report.errors.each do |error|
  puts "ERROR: #{error}"
end

mago

Runtime