Merge pull request rails#49080 from gmcgibbon/generate_correct_cpk_param

Fix to_param id generation for partial composite keys

Author: eileencodes

actionview/test/template/url_helper_test.rb

@@ -1302,7 +1302,7 @@ def setup
     @routes = WorkshopsController::ROUTES
   end
 
-  def test_new_resource
+  def test_index_resource
     @controller = WorkshopsController.new
 
     get :index
@@ -1316,6 +1316,13 @@ def test_existing_resource
     assert_equal %{/workshops/1\n<a href="/workshops/1">Workshop</a>}, @response.body
   end
 
+  def test_existing_cpk_resource
+    @controller = WorkshopsController.new
+
+    get :show, params: { id: "1-27" }
+    assert_equal %{/workshops/1-27\n<a href="/workshops/1-27">Workshop</a>}, @response.body
+  end
+
   def test_current_page_when_options_does_not_respond_to_to_hash
     @controller = WorkshopsController.new
 

activemodel/lib/active_model/conversion.rb

@@ -88,7 +88,7 @@ def to_key
     #   person = Person.new(1)
     #   person.to_param # => "1"
     def to_param
-      (persisted? && key = to_key) ? key.join(self.class.param_delimiter) : nil
+      (persisted? && (key = to_key) && key.all?) ? key.join(self.class.param_delimiter) : nil
     end
 
     # Returns a +string+ identifying the path associated with the object.

activemodel/test/cases/conversion_test.rb

@@ -34,6 +34,10 @@ class ConversionTest < ActiveModel::TestCase
     assert_equal "abc-xyz", Contact.new(id: ["abc", "xyz"]).to_param
   end
 
+  test "to_param returns nil if composite id is incomplete" do
+    assert_nil Contact.new(id: [1, nil]).to_param
+  end
+
   test "to_param returns nil if to_key is nil" do
     klass = Class.new(Contact) do
       def persisted?