validate_absence_of: cast @attribute to String

ActiveRecord.columns_hash returns Hash with String keys.
This is why `it { expect(offer).to validate_absence_of(:expired_at) }`
is not working.

NEWS.md

@@ -24,6 +24,9 @@
   the record had to be persisted in order for the matcher to work. Now this is
   no longer the case and the record can remain unpersisted.
 
+* Fix `validate_absence_of`: it required that a string be passed as the
+  attribute name rather than a symbol (which is the usual and documented usage).
+
 ### Improvements
 
 * `have_and_belongs_to_many` now checks to make sure that the join table
@@ -140,7 +143,7 @@
 * Change `validate_uniqueness_of(...)` so that it provides default values for
   non-nullable attributes.
 
-* Running `rake` now installs Appraisals before running the test suite. 
+* Running `rake` now installs Appraisals before running the test suite.
   (Additionally, we now manage Appraisals using the `appraisal` executable in
   Appraisal 1.0.0.)
 

lib/shoulda/matchers/active_model/validate_absence_of_matcher.rb

@@ -82,8 +82,10 @@ module Shoulda
             else
               obj
             end
-          elsif attribute_class == Fixnum
+          elsif [Fixnum, Float].include?(attribute_class)
             1
+          elsif attribute_class == BigDecimal
+            BigDecimal.new(1, 0)
           elsif !attribute_class || attribute_class == String
             'an arbitrary value'
           else
@@ -93,8 +95,8 @@ module Shoulda
 
         def attribute_class
           @subject.class.respond_to?(:columns_hash) &&
-            @subject.class.columns_hash[@attribute].respond_to?(:klass) &&
-            @subject.class.columns_hash[@attribute].klass
+            @subject.class.columns_hash[@attribute.to_s].respond_to?(:klass) &&
+            @subject.class.columns_hash[@attribute.to_s].klass
         end
 
         def collection?

spec/shoulda/matchers/active_model/validate_absence_of_matcher_spec.rb

@@ -2,6 +2,21 @@ require 'spec_helper'
 
 describe Shoulda::Matchers::ActiveModel::ValidateAbsenceOfMatcher do
   if active_model_4_0?
+    def self.available_column_types
+      [
+        :string,
+        :text,
+        :integer,
+        :float,
+        :decimal,
+        :datetime,
+        :timestamp,
+        :time,
+        :date,
+        :binary
+      ]
+    end
+
     context 'a model with an absence validation' do
       it 'accepts' do
         expect(validating_absence_of(:attr)).to validate_absence_of(:attr)
@@ -10,6 +25,15 @@ describe Shoulda::Matchers::ActiveModel::ValidateAbsenceOfMatcher do
       it 'does not override the default message with a present' do
         expect(validating_absence_of(:attr)).to validate_absence_of(:attr).with_message(nil)
       end
+
+      available_column_types.each do |type|
+        context "when column is of type #{type}" do
+          it "accepts" do
+            expect(validating_absence_of(:attr, {}, type: type)).
+              to validate_absence_of(:attr)
+          end
+        end
+      end
     end
 
     context 'a model without an absence validation' do
@@ -95,9 +119,12 @@ describe Shoulda::Matchers::ActiveModel::ValidateAbsenceOfMatcher do
       end
     end
 
-    def validating_absence_of(attr, options = {})
-      define_model :example, attr => :string do
-        validates_absence_of attr, options
+    def validating_absence_of(attr, validation_options = {}, given_column_options = {})
+      default_column_options = { type: :string, options: {} }
+      column_options = default_column_options.merge(given_column_options)
+
+      define_model :example, attr => column_options do
+        validates_absence_of attr, validation_options
       end.new
     end