Only use the `_before_type_cast` in the form when from user input

While we don't want to change the form input when validations fail,
blindly using `_before_type_cast` will cause the input to display the
wrong data for any type which does additional work on database values.

1 files changed, 17 insertions, 0 deletions

diff --git a/actionview/test/template/form_helper_test.rb b/actionview/test/template/form_helper_test.rb
index fa8d11d08b..e4fd797924 100644
--- a/actionview/test/template/form_helper_test.rb
+++ b/actionview/test/template/form_helper_test.rb
@@ -101,6 +101,7 @@ class FormHelperTest < ActionView::TestCase
     def @post.to_key; [123]; end
     def @post.id; 0; end
     def @post.id_before_type_cast; "omg"; end
+    def @post.id_came_from_user?; true; end
     def @post.to_param; '123'; end
 
     @post.persisted   = true
@@ -908,6 +909,22 @@ class FormHelperTest < ActionView::TestCase
     )
   end
 
+  def test_inputs_dont_use_before_type_cast_when_value_did_not_come_from_user
+    def @post.id_came_from_user?; false; end
+    assert_dom_equal(
+      %{<textarea id="post_id" name="post[id]">\n0</textarea>},
+      text_area("post", "id")
+    )
+  end
+
+  def test_inputs_use_before_typecast_when_object_doesnt_respond_to_came_from_user
+    class << @post; undef id_came_from_user?; end
+    assert_dom_equal(
+      %{<textarea id="post_id" name="post[id]">\nomg</textarea>},
+      text_area("post", "id")
+    )
+  end
+
   def test_text_area_with_html_entities
     @post.body = "The HTML Entity for & is &amp;"
     assert_dom_equal(