2 files changed, 22 insertions, 6 deletions
diff --git a/activemodel/lib/active_model/attribute_methods.rb b/activemodel/lib/active_model/attribute_methods.rb
index b1724c277a..c5f7a21d3f 100644
--- a/activemodel/lib/active_model/attribute_methods.rb
+++ b/activemodel/lib/active_model/attribute_methods.rb
@@ -1,5 +1,6 @@
 require 'active_support/core_ext/hash/keys'
 require 'active_support/core_ext/class/attribute'
+require 'active_support/deprecation'
 
 module ActiveModel
   class MissingAttributeError < NoMethodError
@@ -365,6 +366,16 @@ module ActiveModel
 
           def initialize(options = {})
             options.symbolize_keys!
+
+            if options[:prefix] == '' || options[:suffix] == ''
+              ActiveSupport::Deprecation.warn(
+                "Specifying an empty prefix/suffix for an attribute method is no longer " \
+                "necessary. If the un-prefixed/suffixed version of the method has not been " \
+                "defined when `define_attribute_methods` is called, it will be defined " \
+                "automatically."
+              )
+            end
+
             @prefix, @suffix = options[:prefix] || '', options[:suffix] || ''
             @regex = /^(#{Regexp.escape(@prefix)})(.+?)(#{Regexp.escape(@suffix)})$/
             @method_missing_target = "#{@prefix}attribute#{@suffix}"
diff --git a/activemodel/test/cases/attribute_methods_test.rb b/activemodel/test/cases/attribute_methods_test.rb
index 95a7098ba4..61ff5fca7a 100644
--- a/activemodel/test/cases/attribute_methods_test.rb
+++ b/activemodel/test/cases/attribute_methods_test.rb
@@ -3,8 +3,6 @@ require 'cases/helper'
 class ModelWithAttributes
   include ActiveModel::AttributeMethods
 
-  attribute_method_suffix ''
-
   class << self
     define_method(:bar) do
       'original bar'
@@ -39,8 +37,6 @@ end
 class ModelWithAttributesWithSpaces
   include ActiveModel::AttributeMethods
 
-  attribute_method_suffix ''
-
   def attributes
     { :'foo bar' => 'value of foo bar'}
   end
@@ -54,8 +50,6 @@ end
 class ModelWithWeirdNamesAttributes
   include ActiveModel::AttributeMethods
 
-  attribute_method_suffix ''
-
   class << self
     define_method(:'c?d') do
       'original c?d'
@@ -146,4 +140,15 @@ class AttributeMethodsTest < ActiveModel::TestCase
     assert_equal 'bar', m.foo
     assert_equal 'bar', m.foo_test
   end
+
+  test 'explicitly specifying an empty prefix/suffix is deprecated' do
+    klass = Class.new(ModelWithAttributes)
+
+    assert_deprecated { klass.attribute_method_suffix '' }
+    assert_deprecated { klass.attribute_method_prefix '' }
+
+    klass.define_attribute_methods([:foo])
+
+    assert_equal 'value of foo', klass.new.foo
+  end
 end