Numericality validation of virtual attributes

Commit #18b2859d2522a4866c398b9a32ebc3de4ec79389 broke numericality
validation of virtual attributes in ActiveRecord models. This commit
added a `column_type` method that assumes if `columns_hash` is a thing
then our attribute would be present within it. This is not true for
virtual attributes and leads to:
```
     NoMethodError:
           undefined method `type' for nil:NilClass
         # /Users/bdmac/.gem/ruby/2.2.2/gems/shoulda-matchers-3.0.1/lib/shoulda/matchers/active_model/validate_numericality_of_matcher.rb:442:in
         # `column_type'
```

This adds a check to `column_type` to return nil instead of throwing an
exception if a specified attribute does not exist in the `columns_hash`
because it is virtual.

lib/shoulda/matchers/active_model/validate_numericality_of_matcher.rb

@@ -438,7 +438,8 @@ def given_numeric_column?
         private
 
         def column_type
-          if @subject.class.respond_to?(:columns_hash)
+          if @subject.class.respond_to?(:columns_hash) &&
+              @subject.class.columns_hash[@attribute.to_s]
             @subject.class.columns_hash[@attribute.to_s].type
           end
         end

spec/unit/shoulda/matchers/active_model/validate_numericality_of_matcher_spec.rb

@@ -127,6 +127,13 @@ def default_validation_values
         expect(record).to validate_numericality
       end
 
+      context 'when the attribute is a virtual' do
+        it 'accepts' do
+          record = build_record_validating_numericality_of_virtual_attribute
+          expect(record).to validate_virtual_attribute_numericality
+        end
+      end
+
       context 'when the column is an integer column' do
         it 'raises an IneffectiveTestError' do
           record = build_record_validating_numericality(
@@ -224,6 +231,15 @@ def default_validation_values
         expect(record).to validate_numericality.odd
       end
 
+      context 'when the attribute is a virtual' do
+        it 'accepts' do
+          record = build_record_validating_numericality_of_virtual_attribute(
+            odd: true,
+          )
+          expect(record).to validate_virtual_attribute_numericality.odd
+        end
+      end
+
       context 'when the column is an integer column' do
         it 'accepts (and does not raise an error)' do
           record = build_record_validating_numericality(
@@ -278,6 +294,15 @@ def default_validation_values
         expect(record).to validate_numericality.even
       end
 
+      context 'when the attribute is a virtual' do
+        it 'accepts' do
+          record = build_record_validating_numericality_of_virtual_attribute(
+            even: true,
+          )
+          expect(record).to validate_virtual_attribute_numericality.even
+        end
+      end
+
       context 'when the column is an integer column' do
         it 'accepts (and does not raise an error)' do
           record = build_record_validating_numericality(
@@ -332,6 +357,16 @@ def default_validation_values
         expect(record).to validate_numericality.is_less_than_or_equal_to(18)
       end
 
+      context 'when the attribute is a virtual' do
+        it 'accepts' do
+          record = build_record_validating_numericality_of_virtual_attribute(
+            less_than_or_equal_to: 18,
+          )
+          expect(record).to validate_virtual_attribute_numericality.
+            is_less_than_or_equal_to(18)
+        end
+      end
+
       context 'when the column is an integer column' do
         it 'accepts (and does not raise an error)' do
           record = build_record_validating_numericality(
@@ -390,6 +425,16 @@ def default_validation_values
           is_less_than(18)
       end
 
+      context 'when the attribute is a virtual' do
+        it 'accepts' do
+          record = build_record_validating_numericality_of_virtual_attribute(
+            less_than: 18,
+          )
+          expect(record).to validate_virtual_attribute_numericality.
+            is_less_than(18)
+        end
+      end
+
       context 'when the column is an integer column' do
         it 'accepts (and does not raise an error)' do
           record = build_record_validating_numericality(
@@ -446,6 +491,16 @@ def default_validation_values
         expect(record).to validate_numericality.is_equal_to(18)
       end
 
+      context 'when the attribute is a virtual' do
+        it 'accepts' do
+          record = build_record_validating_numericality_of_virtual_attribute(
+            equal_to: 18,
+          )
+          expect(record).to validate_virtual_attribute_numericality.
+            is_equal_to(18)
+        end
+      end
+
       context 'when the column is an integer column' do
         it 'accepts (and does not raise an error)' do
           record = build_record_validating_numericality(
@@ -504,6 +559,16 @@ def default_validation_values
           is_greater_than_or_equal_to(18)
       end
 
+      context 'when the attribute is a virtual' do
+        it 'accepts' do
+          record = build_record_validating_numericality_of_virtual_attribute(
+            greater_than_or_equal_to: 18,
+          )
+          expect(record).to validate_virtual_attribute_numericality.
+            is_greater_than_or_equal_to(18)
+        end
+      end
+
       context 'when the column is an integer column' do
         it 'accepts (and does not raise an error)' do
           record = build_record_validating_numericality(
@@ -568,6 +633,16 @@ def default_validation_values
           is_greater_than(18)
       end
 
+      context 'when the attribute is a virtual' do
+        it 'accepts' do
+          record = build_record_validating_numericality_of_virtual_attribute(
+            greater_than: 18,
+          )
+          expect(record).to validate_virtual_attribute_numericality.
+            is_greater_than(18)
+        end
+      end
+
       context 'when the column is an integer column' do
         it 'accepts (and does not raise an error)' do
           record = build_record_validating_numericality(
@@ -1141,6 +1216,21 @@ def define_model_validating_numericality(options = {})
     end
   end
 
+  def define_model_validating_numericality_of_virtual_attribute(options = {})
+    virtual_attr = options.delete(:virtual_attribute) do
+      virtual_attribute_name
+    end
+
+    define_model 'Example' do |model|
+      model.send(:attr_accessor, virtual_attr)
+      model.validates_numericality_of(virtual_attr, options)
+    end
+  end
+
+  def build_record_validating_numericality_of_virtual_attribute(options = {})
+    define_model_validating_numericality_of_virtual_attribute(options).new
+  end
+
   def build_record_validating_numericality(options = {})
     define_model_validating_numericality(options).new
   end
@@ -1157,7 +1247,15 @@ def validate_numericality
     validate_numericality_of(attribute_name)
   end
 
+  def validate_virtual_attribute_numericality
+    validate_numericality_of(virtual_attribute_name)
+  end
+
   def attribute_name
     :attr
   end
+
+  def virtual_attribute_name
+    :virtual_attr
+  end
 end