refactor(yield): use yield from syntax

scrapy/core/spidermw.py

@@ -103,8 +103,7 @@ class SpiderMiddlewareManager(MiddlewareManager):
     ) -> Union[Generator, AsyncGenerator]:
         def process_sync(iterable: Iterable) -> Generator:
             try:
-                for r in iterable:
-                    yield r
+                yield from iterable
             except Exception as ex:
                 exception_result = self._process_spider_exception(
                     response, spider, Failure(ex), exception_processor_index

scrapy/spiders/crawl.py

@@ -131,8 +131,7 @@ class CrawlSpider(Spider):
     def _handle_failure(self, failure, errback):
         if errback:
             results = errback(failure) or ()
-            for request_or_item in iterate_spider_output(results):
-                yield request_or_item
+            yield from iterate_spider_output(results)
 
     def _compile_rules(self):
         self._rules = []

scrapy/spiders/feed.py

@@ -58,8 +58,7 @@ class XMLFeedSpider(Spider):
 
         for selector in nodes:
             ret = iterate_spider_output(self.parse_node(response, selector))
-            for result_item in self.process_results(response, ret):
-                yield result_item
+            yield from self.process_results(response, ret)
 
     def _parse(self, response, **kwargs):
         if not hasattr(self, "parse_node"):
@@ -133,8 +132,7 @@ class CSVFeedSpider(Spider):
             response, self.delimiter, self.headers, quotechar=self.quotechar
         ):
             ret = iterate_spider_output(self.parse_row(response, row))
-            for result_item in self.process_results(response, ret):
-                yield result_item
+            yield from self.process_results(response, ret)
 
     def _parse(self, response, **kwargs):
         if not hasattr(self, "parse_row"):

scrapy/spiders/sitemap.py

@@ -33,8 +33,7 @@ class SitemapSpider(Spider):
         attributes, for example, you can filter locs with lastmod greater
         than a given date (see docs).
         """
-        for entry in entries:
-            yield entry
+        yield from entries
 
     def _parse_sitemap(self, response):
         if response.url.endswith("/robots.txt"):

scrapy/utils/python.py

@@ -57,8 +57,7 @@ def iflatten(x: Iterable) -> Iterable:
     Similar to ``.flatten()``, but returns iterator instead"""
     for el in x:
         if is_listlike(el):
-            for el_ in iflatten(el):
-                yield el_
+            yield from iflatten(el)
         else:
             yield el
 

scrapy/utils/request.py

@@ -44,8 +44,7 @@ def _serialize_headers(
     for header in headers:
         if header in request.headers:
             yield header
-            for value in request.headers.getlist(header):
-                yield value
+            yield from request.headers.getlist(header)
 
 
 def request_fingerprint(

tests/spiders.py

@@ -301,8 +301,7 @@ class BrokenStartRequestsSpider(FollowAllSpider):
 
     def parse(self, response):
         self.seedsseen.append(response.meta.get("seed"))
-        for req in super().parse(response):
-            yield req
+        yield from super().parse(response)
 
 
 class SingleRequestSpider(MetaSpider):

tests/test_feedexport.py

@@ -673,8 +673,7 @@ class FeedExportTestBase(ABC, unittest.TestCase):
             name = "testspider"
 
             def parse(self, response):
-                for item in items:
-                    yield item
+                yield from items
 
         data = yield self.run_and_export(TestSpider, settings)
         return data
@@ -2696,8 +2695,7 @@ class BatchDeliveriesTest(FeedExportTestBase):
             name = "testspider"
 
             def parse(self, response):
-                for item in items:
-                    yield item
+                yield from items
 
         with MockServer() as server:
             TestSpider.start_urls = [server.url("/")]

tests/test_spider.py

@@ -317,8 +317,7 @@ class CrawlSpiderTest(SpiderTest):
             rules = (Rule(LinkExtractor(), process_links="dummy_process_links"),)
 
             def dummy_process_links(self, links):
-                for link in links:
-                    yield link
+                yield from links
 
         spider = _CrawlSpider()
         output = list(spider._requests_to_follow(response))

tests/test_spidermiddleware.py

@@ -170,8 +170,7 @@ class BaseAsyncSpiderMiddlewareTestCase(SpiderMiddlewareTestCase):
 
 class ProcessSpiderOutputSimpleMiddleware:
     def process_spider_output(self, response, result, spider):
-        for r in result:
-            yield r
+        yield from result
 
 
 class ProcessSpiderOutputAsyncGenMiddleware:
@@ -182,8 +181,7 @@ class ProcessSpiderOutputAsyncGenMiddleware:
 
 class ProcessSpiderOutputUniversalMiddleware:
     def process_spider_output(self, response, result, spider):
-        for r in result:
-            yield r
+        yield from result
 
     async def process_spider_output_async(self, response, result, spider):
         async for r in result:
@@ -324,8 +322,7 @@ class ProcessSpiderOutputInvalidResult(BaseAsyncSpiderMiddlewareTestCase):
 
 class ProcessStartRequestsSimpleMiddleware:
     def process_start_requests(self, start_requests, spider):
-        for r in start_requests:
-            yield r
+        yield from start_requests
 
 
 class ProcessStartRequestsSimple(BaseAsyncSpiderMiddlewareTestCase):

tests/test_utils_defer.py

@@ -107,8 +107,7 @@ class DeferUtilsTest(unittest.TestCase):
 class IterErrbackTest(unittest.TestCase):
     def test_iter_errback_good(self):
         def itergood():
-            for x in range(10):
-                yield x
+            yield from range(10)
 
         errors = []
         out = list(iter_errback(itergood(), errors.append))