Add allow_nil option to validate_numericality_of

NEWS.md

@@ -30,6 +30,9 @@
 * Additionally, we now manage Appraisals using the `appraisal` executable that
   is coming in Appraisal 1.0.0 (we're using the beta for now).
 
+* Add `allow_nil` option to `validate_numericality_of` so that you can validate
+  that numeric values are validated only if a value is supplied.
+
 # v 2.5.0
 
 * Fix Rails/Test::Unit integration to ensure that the test case classes we are

README.md

@@ -448,6 +448,7 @@ class Person < ActiveRecord::Base
   validates_numericality_of :birth_year, less_than_or_equal_to: 1987
   validates_numericality_of :birth_day, odd: true
   validates_numericality_of :birth_month, even: true
+  validates_numericality_of :rank, less_than_or_equal_to: 10, allow_nil: true
 
   validates_numericality_of :number_of_dependents,
     message: 'Number of dependents must be a number'

lib/shoulda/matchers/active_model/validate_numericality_of_matcher.rb

@@ -10,12 +10,14 @@ module Shoulda # :nodoc:
       # * <tt>only_integer</tt> - allows only integer values
       # * <tt>odd</tt> - Specifies the value must be an odd number.
       # * <tt>even</tt> - Specifies the value must be an even number.
+      # * <tt>allow_nil</tt> - allows nil values
       #
       # Examples:
       #   it { should validate_numericality_of(:price) }
       #   it { should validate_numericality_of(:age).only_integer }
       #   it { should validate_numericality_of(:frequency).odd }
       #   it { should validate_numericality_of(:frequency).even }
+      #   it { should validate_numericality_of(:rank).less_than_or_equal_to(10).allow_nil }
       #
       def validate_numericality_of(attr)
         ValidateNumericalityOfMatcher.new(attr)
@@ -37,6 +39,11 @@ module Shoulda # :nodoc:
           self
         end
 
+        def allow_nil
+          add_submatcher(AllowValueMatcher.new(nil).for(@attribute).with_message(:not_a_number))
+          self
+        end
+
         def is_greater_than(value)
           add_submatcher(NumericalityMatchers::ComparisonMatcher.new(value, :>).for(@attribute))
           self

spec/shoulda/matchers/active_model/validate_numericality_of_matcher_spec.rb

@@ -47,6 +47,19 @@ describe Shoulda::Matchers::ActiveModel::ValidateNumericalityOfMatcher do
     end
   end
 
+  context 'with the allow_nil option' do
+    it 'allows nil values for that attribute' do
+      expect(validating_numericality(allow_nil: true)).to matcher.allow_nil
+    end
+
+    it 'rejects when the model does not allow nil' do
+      the_matcher = matcher.allow_nil
+      expect {
+        expect(validating_numericality).to the_matcher
+      }.to fail_with_message_including('Did not expect errors to include "is not a number"')
+    end
+  end
+
   context 'with the only_integer option' do
     it 'allows integer values for that attribute' do
       expect(validating_numericality(only_integer: true)).to matcher.only_integer