From bb5a57bbdffebcc99cab67b609d5f0e17206a65d Mon Sep 17 00:00:00 2001
From: Victor Ruiz <victorruiz@zyte.com>
Date: Mon, 3 Jun 2024 08:56:58 +0200
Subject: [PATCH] Fix assert onempty nested selectors

---
 itemloaders/__init__.py     | 10 +++++-----
 tests/test_nested_loader.py | 10 ++++++++++
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/itemloaders/__init__.py b/itemloaders/__init__.py
index f13bd77..d90d5f4 100644
--- a/itemloaders/__init__.py
+++ b/itemloaders/__init__.py
@@ -163,7 +163,7 @@ def nested_xpath(self, xpath: str, **context: Any) -> Self:
         :meth:`add_value`, :meth:`replace_value`, etc. will behave as expected.
         """
         self._check_selector_method()
-        assert self.selector
+        assert self.selector is not None
         selector = self.selector.xpath(xpath)
         context.update(selector=selector)
         subloader = self.__class__(item=self.item, parent=self, **context)
@@ -178,7 +178,7 @@ def nested_css(self, css: str, **context: Any) -> Self:
         :meth:`add_value`, :meth:`replace_value`, etc. will behave as expected.
         """
         self._check_selector_method()
-        assert self.selector
+        assert self.selector is not None
         selector = self.selector.css(css)
         context.update(selector=selector)
         subloader = self.__class__(item=self.item, parent=self, **context)
@@ -473,7 +473,7 @@ def _get_xpathvalues(
         self, xpaths: Union[str, Iterable[str]], **kw: Any
     ) -> List[Any]:
         self._check_selector_method()
-        assert self.selector
+        assert self.selector is not None
         xpaths = arg_to_iter(xpaths)
         return flatten(self.selector.xpath(xpath, **kw).getall() for xpath in xpaths)
 
@@ -558,7 +558,7 @@ def get_css(
 
     def _get_cssvalues(self, csss: Union[str, Iterable[str]]) -> List[Any]:
         self._check_selector_method()
-        assert self.selector
+        assert self.selector is not None
         csss = arg_to_iter(csss)
         return flatten(self.selector.css(css).getall() for css in csss)
 
@@ -641,7 +641,7 @@ def get_jmes(
 
     def _get_jmesvalues(self, jmess: Union[str, Iterable[str]]) -> List[Any]:
         self._check_selector_method()
-        assert self.selector
+        assert self.selector is not None
         jmess = arg_to_iter(jmess)
         if not hasattr(self.selector, "jmespath"):
             raise AttributeError(
diff --git a/tests/test_nested_loader.py b/tests/test_nested_loader.py
index 82d24f7..19e4bd3 100644
--- a/tests/test_nested_loader.py
+++ b/tests/test_nested_loader.py
@@ -117,3 +117,13 @@ def test_nested_load_item(self):
         self.assertEqual(item["name"], ["marta"])
         self.assertEqual(item["url"], ["http://www.scrapy.org"])
         self.assertEqual(item["image"], ["/images/logo.png"])
+
+    def test_nested_empty_selector(self):
+        loader = ItemLoader(selector=self.selector)
+        nested_xpath = loader.nested_xpath("//bar")
+        assert isinstance(nested_xpath, ItemLoader)
+        nested_xpath.add_xpath("foo", "./foo")
+
+        nested_css = loader.nested_css("bar")
+        assert isinstance(nested_css, ItemLoader)
+        nested_css.add_css("foo", "foo")