Warn when attempting to set a value to a readonly field

lib/capybara.rb

@@ -15,6 +15,7 @@ module Capybara
   class InfiniteRedirectError < CapybaraError; end
   class ScopeError < CapybaraError; end
   class WindowError < CapybaraError; end
+  class ReadOnlyElementError < CapybaraError; end
 
   class << self
     attr_accessor :asset_host, :app_host, :run_server, :default_host, :always_include_port

lib/capybara/rack_test/node.rb

@@ -27,7 +27,11 @@ class Capybara::RackTest::Node < Capybara::Driver::Node
     elsif input_field?
       set_input(value)
     elsif textarea?
-      native.content = value.to_s unless self[:readonly]
+      if self[:readonly]
+        warn "Attempt to set readonly element with value: #{value} \n * This will raise an exception in a future version of Capybara"
+      else
+        native.content = value.to_s
+      end
     end
   end
 
@@ -165,7 +169,11 @@ private
       end
       native.remove
     else
-      native['value'] = value.to_s unless self[:readonly]
+      if self[:readonly]
+        warn "Attempt to set readonly element with value: #{value} \n *This will raise an exception in a future version of Capybara"
+      else
+        native['value'] = value.to_s
+      end
     end
   end
 

lib/capybara/selenium/node.rb

@@ -37,11 +37,13 @@ class Capybara::Selenium::Node < Capybara::Driver::Node
       path_names = value.to_s.empty? ? [] : value
       native.send_keys(*path_names)
     elsif tag_name == 'textarea' or tag_name == 'input'
-      if value.to_s.empty?
+      if self[:readonly]
+        warn "Attempt to set readonly element with value: #{value} \n *This will raise an exception in a future version of Capybara"
+      elsif value.to_s.empty?
         native.clear
       else
         #script can change a readonly element which user input cannot, so dont execute if readonly
-        driver.browser.execute_script "arguments[0].value = ''", native unless self[:readonly]
+        driver.browser.execute_script "arguments[0].value = ''", native
         native.send_keys(value.to_s)
       end
     elsif native.attribute('isContentEditable')

lib/capybara/spec/session/node_spec.rb

@@ -97,6 +97,10 @@ Capybara::SpecHelper.spec "node" do
       @session.first('//input[@readonly]').set('changed')
       expect(@session.first('//input[@readonly]').value).to eq('should not change')
     end
+    
+    it "should raise if the text field is readonly" do
+      expect(@session.first('//input[@readonly]').set('changed')).to raise_error(Capybara::ReadOnlyElementError)
+    end if Capybara::VERSION.to_f > 3.0
 
     it "should not set if the textarea is readonly" do
       expect(@session.first('//textarea[@readonly]').value).to eq('textarea should not change')
@@ -104,6 +108,10 @@ Capybara::SpecHelper.spec "node" do
       expect(@session.first('//textarea[@readonly]').value).to eq('textarea should not change')
     end
 
+    it "should raise if the text field is readonly" do
+      expect(@session.first('//textarea[@readonly]').set('changed')).to raise_error(Capybara::ReadOnlyElementError)
+    end if Capybara::VERSION.to_f > 3.0
+
     it 'should allow me to change the contents of a contenteditable element', :requires => [:js] do
       @session.visit('/with_js')
       @session.find(:css,'#existing_content_editable').set('WYSIWYG')