Merge pull request rails#55376 from byroot/hwia_transform_keys_fix-2

Fix HashWithIndifferentAccess#transform_keys! to avoid collisions

Author: byroot

activesupport/lib/active_support/hash_with_indifferent_access.rb

@@ -354,21 +354,26 @@ def transform_values(&block)
     NOT_GIVEN = Object.new # :nodoc:
 
     def transform_keys(hash = NOT_GIVEN, &block)
-      return to_enum(:transform_keys) if NOT_GIVEN.equal?(hash) && !block_given?
-      dup.tap { |h| h.transform_keys!(hash, &block) }
+      if NOT_GIVEN.equal?(hash)
+        if block_given?
+          self.class.new(super(&block))
+        else
+          to_enum(:transform_keys)
+        end
+      else
+        self.class.new(super)
+      end
     end
 
     def transform_keys!(hash = NOT_GIVEN, &block)
-      return to_enum(:transform_keys!) if NOT_GIVEN.equal?(hash) && !block_given?
-
-      if hash.nil?
-        super
-      elsif NOT_GIVEN.equal?(hash)
-        keys.each { |key| self[yield(key)] = delete(key) }
-      elsif block_given?
-        keys.each { |key| self[hash[key] || yield(key)] = delete(key) }
+      if NOT_GIVEN.equal?(hash)
+        if block_given?
+          replace(transform_keys(&block))
+        else
+          return to_enum(:transform_keys!)
+        end
       else
-        keys.each { |key| self[hash[key] || key] = delete(key) }
+        replace(transform_keys(hash, &block))
       end
 
       self

activesupport/test/hash_with_indifferent_access_test.rb

@@ -473,6 +473,16 @@ def test_indifferent_transform_keys
     assert_equal(["A", "bbb"], hash.keys) # asserting that order of keys is unchanged
     assert_instance_of ActiveSupport::HashWithIndifferentAccess, hash
 
+    hash = ActiveSupport::HashWithIndifferentAccess.new(@integers).transform_keys { |k| k + 1 }
+
+    assert_equal([1, 2], hash.keys)
+
+    repeating_strings = { "a" => 1, "aa" => 2, "aaa" => 3 }
+
+    hash = ActiveSupport::HashWithIndifferentAccess.new(repeating_strings).transform_keys { |k| "#{k}a" }
+
+    assert_equal(%w[aa aaa aaaa], hash.keys)
+
     assert_raise TypeError do
       hash.transform_keys(nil)
     end