Added support for ignoring_interference_by_writer to validate_uniqueness_of

lib/shoulda/matchers/active_model/validation_matcher.rb

@@ -8,6 +8,7 @@ class ValidationMatcher
         def initialize(attribute)
           @attribute = attribute
           @strict = false
+          @ignoring_interference_by_writer = false
           @failure_message = nil
           @failure_message_when_negated = nil
         end
@@ -22,6 +23,11 @@ def strict
           self
         end
 
+        def ignoring_interference_by_writer
+          @ignoring_interference_by_writer = true
+          self
+        end
+
         def failure_message_when_negated
           @failure_message_when_negated || @failure_message
         end
@@ -71,6 +77,10 @@ def allow_value_matcher(value, message)
             matcher.strict
           end
 
+          if ignoring_interference_by_writer?
+            matcher.ignoring_interference_by_writer
+          end
+
           matcher
         end
 
@@ -86,12 +96,20 @@ def disallow_value_matcher(value, message)
             matcher.strict
           end
 
+          if ignoring_interference_by_writer?
+            matcher.ignoring_interference_by_writer
+          end
+
           matcher
         end
 
         def strict?
           @strict
         end
+
+        def ignoring_interference_by_writer?
+          @ignoring_interference_by_writer
+        end
       end
     end
   end

spec/unit/shoulda/matchers/active_record/validate_uniqueness_of_matcher_spec.rb

@@ -502,6 +502,51 @@
     end
   end
 
+  context 'when the model maps all values to upcase' do
+    let(:add_attribute_upcase_normalization) do
+      lambda do |m|
+        setter_name = "#{attribute_name}=".to_sym
+        attr_name = attribute_name
+        m.class_eval do
+          define_method(setter_name) do |value|
+            upcase_value = value.respond_to?(:upcase) ? value.upcase : value
+            write_attribute(attr_name, upcase_value)
+          end
+        end
+      end
+    end
+
+    context 'when ignoring_interference_by_writer is not specified' do
+      it 'raises a CouldNotSetAttributeError' do
+        record = build_record_validating_uniqueness(
+          attribute_type: :string,
+          validation_options: { case_sensitive: false },
+          &add_attribute_upcase_normalization
+        )
+        running_matcher = lambda do
+          validate_uniqueness.case_insensitive.matches?(record)
+        end
+
+        avm_class = Shoulda::Matchers::ActiveModel::AllowValueMatcher
+        expect(&running_matcher).
+          to raise_error(avm_class::CouldNotSetAttributeError)
+      end
+    end
+
+    context 'when ignoring_interference_by_writer is specified' do
+      it 'accepts' do
+        record = build_record_validating_uniqueness(
+          attribute_type: :string,
+          validation_options: { case_sensitive: false },
+          &add_attribute_upcase_normalization
+        )
+
+        expect(record).to validate_uniqueness.
+          case_insensitive.ignoring_interference_by_writer
+      end
+    end
+  end
+
   context 'when the validation is declared with allow_nil' do
     context 'given a new record whose attribute is nil' do
       it 'accepts' do