CachedInstanceLoader defaults to empty when import_id is missing (#1225)

AUTHORS

@@ -115,3 +115,4 @@ The following is a list of much appreciated contributors:
 * kjpc-tech (Kyle)
 * Matthew Hegarty
 * jinmay (jinmyeong Cho)
+* DonQueso89 (Kees van Ekeren)

import_export/instance_loaders.py

@@ -50,15 +50,21 @@ def __init__(self, *args, **kwargs):
         pk_field_name = self.resource.get_import_id_fields()[0]
         self.pk_field = self.resource.fields[pk_field_name]
 
-        ids = [self.pk_field.clean(row) for row in self.dataset.dict]
-        qs = self.get_queryset().filter(**{
-            "%s__in" % self.pk_field.attribute: ids
-            })
+        # If the pk field is missing, all instances in dataset are new
+        # and cache is empty.
+        self.all_instances = {}
+        if self.dataset.dict and self.pk_field.column_name in self.dataset.dict[0]:
+            ids = [self.pk_field.clean(row) for row in self.dataset.dict]
+            qs = self.get_queryset().filter(**{
+                "%s__in" % self.pk_field.attribute: ids
+                })
 
-        self.all_instances = {
-            self.pk_field.get_value(instance): instance
-            for instance in qs
-        }
+            self.all_instances = {
+                self.pk_field.get_value(instance): instance
+                for instance in qs
+            }
 
     def get_instance(self, row):
-        return self.all_instances.get(self.pk_field.clean(row))
+        if self.all_instances:
+            return self.all_instances.get(self.pk_field.clean(row))
+        return None

tests/core/tests/test_instance_loaders.py

@@ -26,3 +26,28 @@ def test_all_instances(self):
     def test_get_instance(self):
         obj = self.instance_loader.get_instance(self.dataset.dict[0])
         self.assertEqual(obj, self.book)
+
+
+
+class CachedInstanceLoaderWithAbsentImportIdFieldTest(TestCase):
+    """Ensure that the cache is empty when the PK field is absent
+    in the inbound dataset.
+    """
+
+    def setUp(self):
+        self.resource = resources.modelresource_factory(Book)()
+        self.dataset = tablib.Dataset(headers=['name', 'author_email'])
+        self.book = Book.objects.create(name="Some book")
+        self.book2 = Book.objects.create(name="Some other book")
+        row = ['Some book', 'test@example.com']
+        self.dataset.append(row)
+        self.instance_loader = instance_loaders.CachedInstanceLoader(
+            self.resource, self.dataset)
+
+    def test_all_instances(self):
+        self.assertEqual(self.instance_loader.all_instances, {})
+        self.assertEqual(len(self.instance_loader.all_instances), 0)
+
+    def test_get_instance(self):
+        obj = self.instance_loader.get_instance(self.dataset.dict[0])
+        self.assertEqual(obj, None)