Patterns should be activated on demand.

lib/simple_form/helpers/pattern.rb

@@ -5,16 +5,19 @@ module SimpleForm
       private
       
       def add_pattern!
-        input_html_options[:pattern] ||= pattern_source if validate_pattern?
-      end
-
-      def validate_pattern?
-        has_validators? && SimpleForm.html5 &&
-          SimpleForm.browser_validations && pattern_validator.present?
+        input_html_options[:pattern] ||= pattern_source if options[:pattern]
       end
 
       def pattern_source
-        pattern_validator.options[:with].source
+        if options[:pattern] == true
+          if has_validators? && pattern_validator
+            pattern_validator.options[:with].source
+          else
+            raise "Could not find format validator for #{attribute_name}"
+          end
+        else
+          options[:pattern]
+        end
       end
 
       def pattern_validator

test/inputs_test.rb

@@ -335,11 +335,22 @@ class InputTest < ActionView::TestCase
     assert_select 'input[max=119]'
   end
 
-  test 'input should infer pattern from attributes when it is present' do
-    with_input_for @other_validating_user, :country, :string
+  test 'input should infer pattern from attributes when pattern is true' do
+    with_input_for @other_validating_user, :country, :string, :pattern => true
     assert_select 'input[pattern="\w+"]'
   end
 
+  test 'input should use given pattern from attributes' do
+    with_input_for @other_validating_user, :country, :string, :pattern => "\\d+"
+    assert_select 'input[pattern="\d+"]'
+  end
+
+  test 'input should fail if pattern is true but no pattern exists' do
+    assert_raise RuntimeError do
+      with_input_for @other_validating_user, :name, :string, :pattern => true
+    end
+  end
+
   test 'input should have step value of any except for integer attribute' do
     with_input_for @validating_user, :age, :float
     assert_select 'input[step="any"]'