Add change reactor test to CrawlerRunner

.flake8

@@ -9,6 +9,7 @@ exclude =
 per-file-ignores =
 # Exclude files that are meant to provide top-level imports
 # E402: Module level import not at top of file
+    tests/CrawlerRunner/change_reactor.py:E402
 # F401: Module imported but unused
     scrapy/__init__.py:E402
     scrapy/core/downloader/handlers/http.py:F401

scrapy/crawler.py

@@ -129,6 +129,8 @@ class Crawler:
             if is_asyncio_reactor_installed() and event_loop:
                 verify_installed_asyncio_event_loop(event_loop)
 
+            log_reactor_info()
+
         self.extensions = ExtensionManager.from_crawler(self)
         self.settings.freeze()
 

tests/CrawlerRunner/change_reactor.py

@@ -0,0 +1,31 @@
+from scrapy import Spider
+from scrapy.crawler import CrawlerRunner
+from scrapy.utils.log import configure_logging
+
+
+class NoRequestsSpider(Spider):
+    name = "no_request"
+
+    custom_settings = {
+        "TWISTED_REACTOR": "twisted.internet.asyncioreactor.AsyncioSelectorReactor",
+    }
+
+    def start_requests(self):
+        return []
+
+
+configure_logging({"LOG_FORMAT": "%(levelname)s: %(message)s", "LOG_LEVEL": "DEBUG"})
+
+
+from scrapy.utils.reactor import install_reactor
+
+install_reactor("twisted.internet.asyncioreactor.AsyncioSelectorReactor")
+
+runner = CrawlerRunner()
+
+d = runner.crawl(NoRequestsSpider)
+
+from twisted.internet import reactor
+
+d.addBoth(callback=lambda _: reactor.stop())
+reactor.run()

tests/test_crawler.py

@@ -926,3 +926,11 @@ class CrawlerRunnerSubprocess(ScriptRunnerMixin, unittest.TestCase):
         self.assertIn("INFO: Host: not.a.real.domain", log)
         self.assertIn("INFO: Type: <class 'ipaddress.IPv4Address'>", log)
         self.assertIn("INFO: IP address: 127.0.0.1", log)
+
+    def test_change_default_reactor(self):
+        log = self.run_script("change_reactor.py")
+        self.assertIn(
+            "DEBUG: Using reactor: twisted.internet.asyncioreactor.AsyncioSelectorReactor",
+            log,
+        )
+        self.assertIn("DEBUG: Using asyncio event loop", log)