String/Lambda support for conditional attributes/associations

test/serializers/associations_test.rb

@@ -239,27 +239,55 @@ module ActiveModel
           end
         end
 
+        # rubocop:disable Metrics/AbcSize
         def test_conditional_associations
-          serializer = Class.new(ActiveModel::Serializer) do
-            belongs_to :if_assoc_included, if: :true
-            belongs_to :if_assoc_excluded, if: :false
-            belongs_to :unless_assoc_included, unless: :false
-            belongs_to :unless_assoc_excluded, unless: :true
+          model = ::Model.new(true: true, false: false)
 
-            def true
-              true
+          scenarios = [
+            { options: { if:     :true  }, included: true  },
+            { options: { if:     :false }, included: false },
+            { options: { unless: :false }, included: true  },
+            { options: { unless: :true  }, included: false },
+            { options: { if:     'object.true'  }, included: true  },
+            { options: { if:     'object.false' }, included: false },
+            { options: { unless: 'object.false' }, included: true  },
+            { options: { unless: 'object.true'  }, included: false },
+            { options: { if:     -> { object.true }  }, included: true  },
+            { options: { if:     -> { object.false } }, included: false },
+            { options: { unless: -> { object.false } }, included: true  },
+            { options: { unless: -> { object.true }  }, included: false },
+            { options: { if:     -> (s) { s.object.true }  }, included: true  },
+            { options: { if:     -> (s) { s.object.false } }, included: false },
+            { options: { unless: -> (s) { s.object.false } }, included: true  },
+            { options: { unless: -> (s) { s.object.true }  }, included: false }
+          ]
+
+          scenarios.each do |s|
+            serializer = Class.new(ActiveModel::Serializer) do
+              belongs_to :association, s[:options]
+
+              def true
+                true
+              end
+
+              def false
+                false
+              end
             end
 
-            def false
-              false
+            hash = serializable(model, serializer: serializer).serializable_hash
+            assert_equal(s[:included], hash.key?(:association), "Error with #{s[:options]}")
+          end
+        end
+
+        def test_illegal_conditional_associations
+          exception = assert_raises(TypeError) do
+            Class.new(ActiveModel::Serializer) do
+              belongs_to :x, if: nil
             end
           end
 
-          model = ::Model.new
-          hash = serializable(model, serializer: serializer).serializable_hash
-          expected = { if_assoc_included: nil, unless_assoc_included: nil }
-
-          assert_equal(expected, hash)
+          assert_match(/:if should be a Symbol, String or Proc/, exception.message)
         end
       end
     end