did_you_mean

Installation

Ruby 2.3 and later ships with this gem and it will automatically be required when a Ruby process starts up. No special setup is required.

Examples

NameError

Correcting a Misspelled Method Name

methosd
# => NameError: undefined local variable or method `methosd' for main:Object
#    Did you mean?  methods
#                   method

Correcting a Misspelled Class Name

OBject
# => NameError: uninitialized constant OBject
#    Did you mean?  Object

Suggesting an Instance Variable Name

@full_name = "Yuki Nishijima"
first_name, last_name = full_name.split(" ")
# => NameError: undefined local variable or method `full_name' for main:Object
#    Did you mean?  @full_name

Correcting a Class Variable Name

@@full_name = "Yuki Nishijima"
@@full_anme
# => NameError: uninitialized class variable @@full_anme in Object
#    Did you mean?  @@full_name

NoMethodError

full_name = "Yuki Nishijima"
full_name.starts_with?("Y")
# => NoMethodError: undefined method `starts_with?' for "Yuki Nishijima":String
#    Did you mean?  start_with?

KeyError

hash = {foo: 1, bar: 2, baz: 3}
hash.fetch(:fooo)
# => KeyError: key not found: :fooo
#    Did you mean?  :foo

Experimental Features

Aside from the basic features above, the did_you_mean gem comes with experimental features. They can be enabled by calling require 'did_you_mean/experimental'.

Note that these experimental features should never be enabled in production as they would impact Ruby's performance and use some unstable Ruby APIs.

Correcting an Instance Variable When It's Incorrectly Spelled

require 'did_you_mean/experimental'

@full_name = "Yuki Nishijima"
@full_anme.split(" ")
# => NoMethodError: undefined method `split' for nil:NilClass
#    Did you mean?  @full_name

Displaying a Warning When `initialize` is Incorrectly Spelled

require 'did_you_mean/experimental'

class Person
  def intialize
    #...
  end
end
# => warning: intialize might be misspelled, perhaps you meant initialize?

Verbose Formatter

This verbose formatter changes the error message format to take more lines/spaces so it'll be slightly easier to read the suggestions. This formatter can totally be used in any environment including production.

OBject
# => NameError: uninitialized constant OBject
#    Did you mean?  Object

require 'did_you_mean/verbose'
OBject
# => NameError: uninitialized constant OBject
#
#        Did you mean? Object
#

Using the `::DidYouMean::SpellChecker`

If you need to programmatically find the closest matches to the user input, you could do so by re-using the ::DidYouMean::SpellChecker object.

spell_checker = DidYouMean::SpellChecker.new(dictionary: ['email', 'fail', 'eval'])

spell_checker.correct('meail') # => ['email']
spell_checker.correct('afil')  # => ['fail']

Disabling `did_you_mean`

Occasionally, you may want to disable the did_you_mean gem for e.g. debugging issues in the error object itself. You can disable it entirely by specifying --disable-did_you_mean option to the ruby command:

$ ruby --disable-did_you_mean -e "1.zeor?"
-e:1:in `<main>': undefined method `zeor?' for 1:Integer (NameError)

When you do not have direct access to the ruby command (e.g. rails console, irb), you could applyoptions using the RUBYOPT environment variable:

$ RUBYOPT='--disable-did_you_mean' irb
irb:0> 1.zeor?
# => NoMethodError (undefined method `zeor?' for 1:Integer)

Getting the original error message

Sometimes, you do not want to disable the gem entirely, but need to get the original error message without suggestions (e.g. testing). In this case, you could use the #original_message method on the error object:

no_method_error = begin
                    1.zeor?
                  rescue NoMethodError => error
                    error
                  end

no_method_error.message
# => NoMethodError (undefined method `zeor?' for 1:Integer)
#    Did you mean?  zero?

no_method_error.original_message
# => NoMethodError (undefined method `zeor?' for 1:Integer)

Benchmarking

Performance is very important as the did_you_mean gem attempts to find the closest matches on the fly right after an exception is thrown. You could use the following rake tasks to get insights into how the gem performs:

bundle exec rake benchmark:ips:jaro
bundle exec rake benchmark:ips:levenshtein
bundle exec rake benchmark:memory
bundle exec rake benchmark:memory:jaro
bundle exec rake benchmark:memory:levenshtein

Be sure to always use bundle exec otherwise it will activate the pre-installed version of the did_you_mean gem rather than using what's in the lib/.

You could also use the benchmark-driver gem to know how each Ruby performs differently.

bundle exec benchmark-driver benchmark/speed.yml --rbenv '2.6.0 --jit;2.6.0;2.5.3;truffleruby-1.0.0-rc10' --run-duration 30

Contributing

Fork it (https://github.com/ruby/did_you_mean/fork)
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Make sure all tests pass (bundle exec rake)
Push to the branch (git push origin my-new-feature)
Create new Pull Request