From b587b0043945b76640a572786bcb636a4a566163 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Adri=C3=A1n=20Chaves?= <adrian@chaves.io>
Date: Sat, 15 Mar 2025 00:26:24 +0100
Subject: [PATCH] Complete text coverage for exception scenarios of
 Spider.yield_seeds

---
 scrapy/core/engine.py            |  8 ++--
 tests/test_spider_yield_seeds.py | 63 ++++++++++++++++++++++++++------
 2 files changed, 56 insertions(+), 15 deletions(-)

diff --git a/scrapy/core/engine.py b/scrapy/core/engine.py
index ef18afb6f..ef3d91606 100644
--- a/scrapy/core/engine.py
+++ b/scrapy/core/engine.py
@@ -9,6 +9,7 @@ from __future__ import annotations
 
 import logging
 from time import time
+from traceback import format_exc
 from typing import TYPE_CHECKING, Any, TypeVar, cast
 
 from twisted.internet.defer import Deferred, inlineCallbacks, succeed
@@ -196,12 +197,11 @@ class ExecutionEngine:
         except CloseSpider:
             self._seeds = None
             raise
-        except Exception:
+        except Exception as exception:
             self._seeds = None
+            exception_traceback = format_exc()
             logger.error(
-                "Error while reading seeds",
-                exc_info=True,
-                extra={"spider": self.spider},
+                f"Error while reading seeds: {exception}.\n{exception_traceback}"
             )
         else:
             if isinstance(seed, Request):
diff --git a/tests/test_spider_yield_seeds.py b/tests/test_spider_yield_seeds.py
index f7fd7beed..d214ad45f 100644
--- a/tests/test_spider_yield_seeds.py
+++ b/tests/test_spider_yield_seeds.py
@@ -136,18 +136,59 @@ class MainTestCase(TestCase):
 
         await self._test_yield_seeds(yield_seeds, [ITEM_A])
 
-    # Exceptions
+    # Bad definitions.
 
     @deferred_f_from_coro_f
-    async def test_non_generator_async_def(self):
-        class TestSpider(Spider):
-            name = "test"
+    async def test_async_function(self):
+        async def yield_seeds(spider):
+            return
 
-            async def yield_seeds(self):
-                return
-
-        crawler = get_crawler(TestSpider)
         with LogCapture() as log:
-            await maybe_deferred_to_future(crawler.crawl())
-        assert crawler.stats.get_value("finish_reason") == "finished"
-        assert "TestSpider.yield_seeds must be an async generator function" in str(log)
+            await self._test_yield_seeds(yield_seeds, [])
+
+        assert ".yield_seeds must be an async generator function" in str(log)
+
+    @deferred_f_from_coro_f
+    async def test_sync_function(self):
+        def yield_seeds(spider):
+            return []
+
+        with LogCapture() as log:
+            await self._test_yield_seeds(yield_seeds, [])
+
+        assert ".yield_seeds must be an async generator function" in str(log)
+
+    @deferred_f_from_coro_f
+    async def test_sync_generator(self):
+        def yield_seeds(spider):
+            return
+            yield
+
+        with LogCapture() as log:
+            await self._test_yield_seeds(yield_seeds, [])
+
+        assert ".yield_seeds must be an async generator function" in str(log)
+
+    # Exceptions during iteration.
+
+    @deferred_f_from_coro_f
+    async def test_exception_before_yield(self):
+        async def yield_seeds(spider):
+            raise RuntimeError
+            yield
+
+        with LogCapture() as log:
+            await self._test_yield_seeds(yield_seeds, [])
+
+        assert "in yield_seeds\n    raise RuntimeError" in str(log), log
+
+    @deferred_f_from_coro_f
+    async def test_exception_after_yield(self):
+        async def yield_seeds(spider):
+            yield ITEM_A
+            raise RuntimeError
+
+        with LogCapture() as log:
+            await self._test_yield_seeds(yield_seeds, [ITEM_A])
+
+        assert "in yield_seeds\n    raise RuntimeError" in str(log), log