Don't try to close ExecutionEngine.downloader when it doesn't exist. (#6867)

scrapy/core/engine.py

@@ -170,7 +170,8 @@ class ExecutionEngine:
             return self.close_spider(
                 self.spider, reason="shutdown"
             )  # will also close downloader
-        self.downloader.close()
+        if hasattr(self, "downloader"):
+            self.downloader.close()
         return succeed(None)
 
     def pause(self) -> None:

tests/test_engine.py

@@ -22,6 +22,7 @@ from unittest.mock import Mock
 from urllib.parse import urlparse
 
 import attr
+import pytest
 from itemadapter import ItemAdapter
 from pydispatch import dispatcher
 from twisted.internet import defer, reactor
@@ -431,6 +432,19 @@ class TestEngine(TestEngineBase):
         e = ExecutionEngine(get_crawler(MySpider), lambda _: None)
         yield e.close()
 
+    def test_close_without_downloader(self):
+        class CustomException(Exception):
+            pass
+
+        class BadDownloader:
+            def __init__(self, crawler):
+                raise CustomException
+
+        with pytest.raises(CustomException):
+            ExecutionEngine(
+                get_crawler(MySpider, {"DOWNLOADER": BadDownloader}), lambda _: None
+            )
+
     @defer.inlineCallbacks
     def test_start_already_running_exception(self):
         e = ExecutionEngine(get_crawler(MySpider), lambda _: None)