[itemloader-errors] updated Compose and MapCompose messages and added tests

#3836

scrapy/loader/processors.py

@@ -28,10 +28,12 @@ class MapCompose(object):
                 try:
                     next_values += arg_to_iter(func(v))
                 except Exception as e:
+                    type_name = type(func).__name__
+                    _name = (func.__name__ if type_name == 'function'
+                             else type_name)
                     raise ValueError("Error in MapCompose with "
                                      "function %s value=%r error='%s: %s'" %
-                                     (func.__name__, value,
-                                      type(e).__name__, str(e)))
+                                     (_name, value, type(e).__name__, str(e)))
             values = next_values
         return values
 
@@ -55,10 +57,12 @@ class Compose(object):
             try:
                 value = func(value)
             except Exception as e:
+                type_name = type(func).__name__
+                _name = (func.__name__ if type_name == 'function' 
+                         else type_name)
                 raise ValueError("Error in Compose with "
                                  "function %s value=%r error='%s: %s'" %
-                                 (func.__name__, value,
-                                  type(e).__name__, str(e)))
+                                 (_name, value, type(e).__name__, str(e)))
         return value
 
 

tests/test_loader.py

@@ -456,6 +456,42 @@ class BasicItemLoaderTest(unittest.TestCase):
             'title': [u'Test item title 3', u'Test item 4'],
         })
 
+    def test_error_input_processor(self):
+        class TestItem(Item):
+            name = Field()
+
+        class TestItemLoader(ItemLoader):
+            default_item_class = TestItem
+            name_in = MapCompose(float)
+
+        il = TestItemLoader()
+        self.assertRaises(ValueError, il.add_value, 'name',
+                          [u'marta', u'other'])
+
+    def test_error_output_processor(self):
+        class TestItem(Item):
+            name = Field()
+
+        class TestItemLoader(ItemLoader):
+            default_item_class = TestItem
+            name_out = Compose(Join(), float)
+
+        il = TestItemLoader()
+        il.add_value('name', u'marta')
+        with self.assertRaises(ValueError):
+            il.load_item()
+
+    def test_error_processor_as_argument(self):
+        class TestItem(Item):
+            name = Field()
+
+        class TestItemLoader(ItemLoader):
+            default_item_class = TestItem
+
+        il = TestItemLoader()
+        self.assertRaises(ValueError, il.add_value, 'name',
+                          [u'marta', u'other'], Compose(float))
+
 
 class ProcessorsTest(unittest.TestCase):