Do nothing when the same block is included again.

If the same block is included multiple times, we no longer raise an exception
or overwrite the included block instance variable.

Fixes #14802.

[Mark J. Titorenko + Vlad Bokov]

activesupport/CHANGELOG.md

+*   If the same block is `included` multiple times for a Concern, an exception is no longer raised.
+
+    *Mark J. Titorenko*, *Vlad Bokov*
+
 *   Fix bug where `#to_options` for `ActiveSupport::HashWithIndifferentAccess`
     would not act as alias for `#symbolize_keys`.
 

activesupport/lib/active_support/concern.rb

@@ -125,9 +125,13 @@ def append_features(base)
 
     def included(base = nil, &block)
       if base.nil?
-        raise MultipleIncludedBlocks if instance_variable_defined?(:@_included_block)
-
-        @_included_block = block
+        if instance_variable_defined?(:@_included_block)
+          if @_included_block.source_location != block.source_location
+            raise MultipleIncludedBlocks
+          end
+        else
+          @_included_block = block
+        end
       else
         super
       end

activesupport/test/concern_test.rb

@@ -128,4 +128,12 @@ def test_raise_on_multiple_included_calls
       end
     end
   end
+
+  def test_no_raise_on_same_included_call
+    assert_nothing_raised do
+      2.times do
+        load File.expand_path("../fixtures/concern/some_concern.rb", __FILE__)
+      end
+    end
+  end
 end

activesupport/test/fixtures/concern/some_concern.rb

+# frozen_string_literal: true
+
+require "active_support/concern"
+
+module SomeConcern
+  extend ActiveSupport::Concern
+
+  included do
+    # shouldn't raise when module is loaded more than once
+  end
+end