Changed call to label_text to always pass the new thrid parameter, and made the default a proc that ignores it. This is a breaking change.

lib/simple_form.rb

@@ -66,7 +66,7 @@ module SimpleForm
 
   # How the label text should be generated altogether with the required text.
   mattr_accessor :label_text
-  @@label_text = lambda { |label, required| "#{required} #{label}" }
+  @@label_text = proc { |label, required| "#{required} #{label}" }
 
   # You can define the class to be used on all labels. Defaults to none.
   mattr_accessor :label_class

lib/simple_form/components/labels.rb

@@ -30,11 +30,7 @@ module SimpleForm
       end
 
       def label_text
-        @label_text_extended ||= SimpleForm.label_text.parameters.size == 3
-        (@label_text_extended ?
-          SimpleForm.label_text.call(raw_label_text, required_label_text, options[:label].present?) :
-          SimpleForm.label_text.call(raw_label_text, required_label_text))
-        .strip.html_safe
+        SimpleForm.label_text.call(raw_label_text, required_label_text, options[:label].present?).strip.html_safe
       end
 
       def label_target

test/form_builder/label_test.rb

@@ -63,21 +63,21 @@ class LabelTest < ActionView::TestCase
   end
 
   test 'builder allows label order to be changed' do
-    swap SimpleForm, label_text: lambda { |l, r| "#{l}:" } do
+    swap SimpleForm, label_text: proc { |l, r| "#{l}:" } do
       with_label_for @user, :age
       assert_select 'label.integer[for=user_age]', "Age:"
     end
   end
 
   test 'builder should allow custom formatting when label is explicitly specified' do
-    swap SimpleForm, label_text: lambda {|l, r, explicit| explicit ? l : "#{l.titleize}:" } do
+    swap SimpleForm, label_text: proc {|l, r, explicit| explicit ? l : "#{l.titleize}:" } do
       with_label_for @user, :time_zone, 'What is your home time zone?'
       assert_select 'label[for=user_time_zone]', 'What is your home time zone?'
     end
   end
 
   test 'builder should allow custom formatting when label is generated' do
-    swap SimpleForm, label_text: lambda {|l, r, explicit| explicit ? l : "#{l.titleize}:" } do
+    swap SimpleForm, label_text: proc {|l, r, explicit| explicit ? l : "#{l.titleize}:" } do
       with_label_for @user, :time_zone
       assert_select 'label[for=user_time_zone]', 'Time Zone:'
     end