Cherry-pick assoc names for model

lib/rom/factory/tuple_evaluator.rb

@@ -26,8 +26,8 @@ def initialize(attributes, relation, traits = {})
         @sequence = Sequences[relation]
       end
 
-      def model(traits)
-        @relation.combine(*assoc_names(traits)).mapper.model
+      def model(traits, combine: assoc_names(traits))
+        @relation.combine(*combine).mapper.model
       end
 
       # @api private
@@ -51,22 +51,25 @@ def struct(*traits, **attrs)
 
         attributes.merge!(materialized_callables)
 
-        associations = assoc_names(traits)
-          .reject { |name| attrs.key?(name) && attrs[name].nil? }
+        associations = attrs.slice(*assoc_names(traits)).merge(assoc_names(traits)
+          .select { |key|
+            build_assoc?(key, attributes)
+          }
           .map { |key|
-            if (assoc = @attributes[key]) && assoc.count.positive?
-              [key, build_assoc_attrs(key, attributes[relation.primary_key], attributes[key])]
-            end
+            [key, build_assoc_attrs(key, attributes[relation.primary_key], attributes[key])]
           }
-          .compact
-          .to_h
+          .to_h)
 
         attributes = relation.output_schema[attributes]
         attributes.update(associations)
 
         model(traits).new(attributes)
       end
 
+      def build_assoc?(key, attributes)
+        attributes.key?(key) && attributes[key] != [] && !attributes[key].nil?
+      end
+
       def build_assoc_attrs(key, fk, value)
         if value.is_a?(Array)
           value.map { |el| build_assoc_attrs(key, fk, el) }

spec/integration/rom/factory_spec.rb

@@ -54,6 +54,9 @@
         end
 
         factories.define(:user) do |f|
+          f.first_name "Jane"
+          f.last_name "Doe"
+          f.email "[email protected]"
           f.timestamps
           f.association(:tasks, count: 2)
         end
@@ -69,6 +72,18 @@
         expect(user_with_tasks.tasks).to all(have_attributes(user_id: user_with_tasks.id))
       end
 
+      it "sets a value explicitly" do
+        user = factories.structs[:user, tasks: []]
+
+        expect(user.tasks).to be_empty
+      end
+
+      it "sets a value explicitly when persisting" do
+        user = factories[:user, tasks: []]
+
+        expect(user.tasks).to be_empty
+      end
+
       it "does not create records when building child" do
         factories.structs[:task]
 
@@ -111,13 +126,13 @@
         it "does not build associated struct if it's set to nil explicitly" do
           task = factories.structs[:task, user: nil]
 
-          expect(task.user).to be_nil
+          expect(task.user).to be(nil)
         end
 
         it "does not persist associated struct if it's set to nil explicitly" do
           task = factories[:task, user: nil]
 
-          expect(task.user).to be_nil
+          expect(task.user).to be(nil)
         end
 
         it "creates the associated record with provided attributes" do