Add assigned_attribute_names method to return the names of attributes last passed to assign_form_attributes method

Author: Intrepidd

lib/hyper_active_form/base.rb

@@ -19,6 +19,10 @@ class Base
 
     define_model_callbacks :assign_form_attributes, :submit
 
+    # The list of attribute names that have been passed to the form
+    # during the last call to `assign_form_attributes` or `submit`
+    attr_reader :assigned_attribute_names
+
     # Defines to which object the form should delegate the active model methods
     # This is useful so `form_for`/`form_with` can automatically deduce the url and method to use
     #
@@ -53,6 +57,7 @@ def assign_form_attributes(params)
           default_value = self.class._default_attributes[attribute]&.value_before_type_cast
           public_send(:"#{attribute}=", params&.dig(attribute) || default_value)
         end
+        @assigned_attribute_names = params.slice(*attribute_names).keys
       end
     end
 

spec/hyper_active_form/base_spec.rb

@@ -118,6 +118,33 @@ def perform
     end
   end
 
+  describe "#assigned_attribute_names" do
+    context "passing some attributes" do
+      it "returns the list of attributes" do
+        form = dummy_class.new(name: "John", age: 20)
+        form.submit(name: "Fred", age: 19)
+        expect(form.assigned_attribute_names).to eq(%w[name age])
+      end
+    end
+
+    context "passing all attributes" do
+      it "returns the list of attributes" do
+        form = dummy_class.new(name: "John", age: 20)
+        form.submit(name: "Fred", age: 19, hobbies: ["reading", "coding"])
+        expect(form.assigned_attribute_names).to eq(%w[name age hobbies])
+      end
+    end
+
+    context "multiple calls" do
+      it "returns the last list of attributes" do
+        form = dummy_class.new(name: "John", age: 20)
+        form.submit(name: "Fred", age: 19, hobbies: ["reading", "coding"])
+        form.submit(name: "John", age: 20)
+        expect(form.assigned_attribute_names).to eq(%w[name age])
+      end
+    end
+  end
+
   describe ".proxy_for" do
     let(:dummy_class) do
       Class.new(HyperActiveForm::Base) do