Repository: scrapy/scrapy (python)

Issue:
Simplify create_instance calls
Calling https://github.com/scrapy/scrapy/blob/bbfa185664cef79299b48cb0ae22065439bb07fc/scrapy/utils/misc.py#L144 with a crawler is needlessly verbose:

```python
create_instance(objclass, settings=None, crawler=crawler)
create_instance(objclass, settings=crawler.settings, crawler=crawler)  # functionally identical
```

It would be great if we could support a shorter alternative:

```python
create_instance(objclass, crawler=crawler)
```

It is not trivial to do in a backward-compatible way, given the function signature.

It may be also a good idea to log deprecation warnings when `settings` and `crawler` are used as positional arguments, as well as when `objcls` is used as a named parameter, so that we can eventually stop supporting that and move to a better signature:

```python
def create_instance(objcls, /, *args, crawler=None, settings=None, **kwargs): 
```

Although, looking at it now, I realize that such a signature would cause `settings` and `crawler` to be after `*args`, which could be confusing. Maybe it would be best to go for separate functions:

```python
def build_from_crawler(objcls, crawler, /, *args, **kwargs):
def build_from_settings(objcls, settings, /, *args, **kwargs):
```



Pull request:
Converting create_instance to 2 separate functions
Converted `create_instance` to 2 separate functions (`build_from_crawler` and `build_from_settings`).
Changed other calls to `create_instance` in other files.
Added tests for the new functions.

Fixes #5523, closes #5884, closes #6162.


Patch:
diff --git a/scrapy/addons.py b/scrapy/addons.py
index 9060d4f3f..65d7a0310 100644
--- a/scrapy/addons.py
+++ b/scrapy/addons.py
@@ -4,7 +4,7 @@ from typing import TYPE_CHECKING, Any, List
 from scrapy.exceptions import NotConfigured
 from scrapy.settings import Settings
 from scrapy.utils.conf import build_component_list
-from scrapy.utils.misc import create_instance, load_object
+from scrapy.utils.misc import build_from_crawler, load_object
 
 if TYPE_CHECKING:
     from scrapy.crawler import Crawler
@@ -32,9 +32,7 @@ class AddonManager:
         for clspath in build_component_list(settings["ADDONS"]):
             try:
                 addoncls = load_object(clspath)
-                addon = create_instance(
-                    addoncls, settings=settings, crawler=self.crawler
-                )
+                addon = build_from_crawler(addoncls, self.crawler)
                 addon.update_settings(settings)
                 self.addons.append(addon)
             except NotConfigured as e:
diff --git a/scrapy/core/downloader/contextfactory.py b/scrapy/core/downloader/contextfactory.py
index 909cc273f..dba4d8cdc 100644
--- a/scrapy/core/downloader/contextfactory.py
+++ b/scrapy/core/downloader/contextfactory.py
@@ -20,7 +20,7 @@ from scrapy.core.downloader.tls import (
     openssl_methods,
 )
 from scrapy.settings import BaseSettings
-from scrapy.utils.misc import create_instance, load_object
+from scrapy.utils.misc import build_from_crawler, load_object
 
 if TYPE_CHECKING:
     from twisted.internet._sslverify import ClientTLSOptions
@@ -165,18 +165,16 @@ def load_context_factory_from_settings(settings, crawler):
     context_factory_cls = load_object(settings["DOWNLOADER_CLIENTCONTEXTFACTORY"])
     # try method-aware context factory
     try:
-        context_factory = create_instance(
-            objcls=context_factory_cls,
-            settings=settings,
-            crawler=crawler,
+        context_factory = build_from_crawler(
+            context_factory_cls,
+            crawler,
             method=ssl_method,
         )
     except TypeError:
         # use context factory defaults
-        context_factory = create_instance(
-            objcls=context_factory_cls,
-            settings=settings,
-            crawler=crawler,
+        context_factory = build_from_crawler(
+            context_factory_cls,
+            crawler,
         )
         msg = (
             f"{settings['DOWNLOADER_CLIENTCONTEXTFACTORY']} does not accept "
diff --git a/scrapy/core/downloader/handlers/__init__.py b/scrapy/core/downloader/handlers/__init__.py
index 6a211aafa..416669b7f 100644
--- a/scrapy/core/downloader/handlers/__init__.py
+++ b/scrapy/core/downloader/handlers/__init__.py
@@ -9,7 +9,7 @@ from twisted.internet.defer import Deferred
 from scrapy import Request, Spider, signals
 from scrapy.exceptions import NotConfigured, NotSupported
 from scrapy.utils.httpobj import urlparse_cached
-from scrapy.utils.misc import create_instance, load_object
+from scrapy.utils.misc import build_from_crawler, load_object
 from scrapy.utils.python import without_none_values
 
 if TYPE_CHECKING:
@@ -55,10 +55,9 @@ class DownloadHandlers:
             dhcls = load_object(path)
             if skip_lazy and getattr(dhcls, "lazy", True):
                 return None
-            dh = create_instance(
-                objcls=dhcls,
-                settings=self._crawler.settings,
-                crawler=self._crawler,
+            dh = build_from_crawler(
+                dhcls,
+                self._crawler,
             )
         except NotConfigured as ex:
             self._notconfigured[scheme] = str(ex)
diff --git a/scrapy/core/downloader/handlers/http10.py b/scrapy/core/downloader/handlers/http10.py
index 6c1dac4a5..b6ac7a251 100644
--- a/scrapy/core/downloader/handlers/http10.py
+++ b/scrapy/core/downloader/handlers/http10.py
@@ -1,6 +1,6 @@
 """Download handlers for http and https schemes
 """
-from scrapy.utils.misc import create_instance, load_object
+from scrapy.utils.misc import build_from_crawler, load_object
 from scrapy.utils.python import to_unicode
 
 
@@ -30,10 +30,9 @@ class HTTP10DownloadHandler:
 
         host, port = to_unicode(factory.host), factory.port
         if factory.scheme == b"https":
-            client_context_factory = create_instance(
-                objcls=self.ClientContextFactory,
-                settings=self._settings,
-                crawler=self._crawler,
+            client_context_factory = build_from_crawler(
+                self.ClientContextFactory,
+                self._crawler,
             )
             return reactor.connectSSL(host, port, factory, client_context_factory)
         return reactor.connectTCP(host, port, factory)
diff --git a/scrapy/core/downloader/handlers/s3.py b/scrapy/core/downloader/handlers/s3.py
index 81d8e8115..1f7533759 100644
--- a/scrapy/core/downloader/handlers/s3.py
+++ b/scrapy/core/downloader/handlers/s3.py
@@ -2,7 +2,7 @@ from scrapy.core.downloader.handlers.http import HTTPDownloadHandler
 from scrapy.exceptions import NotConfigured
 from scrapy.utils.boto import is_botocore_available
 from scrapy.utils.httpobj import urlparse_cached
-from scrapy.utils.misc import create_instance
+from scrapy.utils.misc import build_from_crawler
 
 
 class S3DownloadHandler:
@@ -50,10 +50,9 @@ class S3DownloadHandler:
                 )
             )
 
-        _http_handler = create_instance(
-            objcls=httpdownloadhandler,
-            settings=settings,
-            crawler=crawler,
+        _http_handler = build_from_crawler(
+            httpdownloadhandler,
+            crawler,
         )
         self._download_http = _http_handler.download_request
 
diff --git a/scrapy/core/engine.py b/scrapy/core/engine.py
index dd1f56f8c..545cd401f 100644
--- a/scrapy/core/engine.py
+++ b/scrapy/core/engine.py
@@ -34,7 +34,7 @@ from scrapy.settings import BaseSettings, Settings
 from scrapy.signalmanager import SignalManager
 from scrapy.spiders import Spider
 from scrapy.utils.log import failure_to_exc_info, logformatter_adapter
-from scrapy.utils.misc import create_instance, load_object
+from scrapy.utils.misc import build_from_crawler, load_object
 from scrapy.utils.reactor import CallLaterOnce
 
 if TYPE_CHECKING:
@@ -358,9 +358,7 @@ class ExecutionEngine:
             raise RuntimeError(f"No free spider slot when opening {spider.name!r}")
         logger.info("Spider opened", extra={"spider": spider})
         nextcall = CallLaterOnce(self._next_request)
-        scheduler = create_instance(
-            self.scheduler_cls, settings=None, crawler=self.crawler
-        )
+        scheduler = build_from_crawler(self.scheduler_cls, self.crawler)
         start_requests = yield self.scraper.spidermw.process_start_requests(
             start_requests, spider
         )
diff --git a/scrapy/core/scheduler.py b/scrapy/core/scheduler.py
index 17c95f1ea..f41b83a67 100644
--- a/scrapy/core/scheduler.py
+++ b/scrapy/core/scheduler.py
@@ -14,7 +14,7 @@ from scrapy.http.request import Request
 from scrapy.spiders import Spider
 from scrapy.statscollectors import StatsCollector
 from scrapy.utils.job import job_dir
-from scrapy.utils.misc import create_instance, load_object
+from scrapy.utils.misc import build_from_crawler, load_object
 
 if TYPE_CHECKING:
     # typing.Self requires Python 3.11
@@ -202,7 +202,7 @@ class Scheduler(BaseScheduler):
         """
         dupefilter_cls = load_object(crawler.settings["DUPEFILTER_CLASS"])
         return cls(
-            dupefilter=create_instance(dupefilter_cls, crawler.settings, crawler),
+            dupefilter=build_from_crawler(dupefilter_cls, crawler),
             jobdir=job_dir(crawler.settings),
             dqclass=load_object(crawler.settings["SCHEDULER_DISK_QUEUE"]),
             mqclass=load_object(crawler.settings["SCHEDULER_MEMORY_QUEUE"]),
@@ -322,10 +322,9 @@ class Scheduler(BaseScheduler):
 
     def _mq(self):
         """Create a new priority queue instance, with in-memory storage"""
-        return create_instance(
+        return build_from_crawler(
             self.pqclass,
-            settings=None,
-            crawler=self.crawler,
+            self.crawler,
             downstream_queue_cls=self.mqclass,
             key="",
         )
@@ -334,10 +333,9 @@ class Scheduler(BaseScheduler):
         """Create a new priority queue instance, with disk storage"""
         assert self.dqdir
         state = self._read_dqs_state(self.dqdir)
-        q = create_instance(
+        q = build_from_crawler(
             self.pqclass,
-            settings=None,
-            crawler=self.crawler,
+            self.crawler,
             downstream_queue_cls=self.dqclass,
             key=self.dqdir,
             startprios=state,
diff --git a/scrapy/crawler.py b/scrapy/crawler.py
index 1d3a11208..844d5f759 100644
--- a/scrapy/crawler.py
+++ b/scrapy/crawler.py
@@ -39,7 +39,7 @@ from scrapy.utils.log import (
     log_reactor_info,
     log_scrapy_info,
 )
-from scrapy.utils.misc import create_instance, load_object
+from scrapy.utils.misc import build_from_crawler, load_object
 from scrapy.utils.ossignal import install_shutdown_handlers, signal_names
 from scrapy.utils.reactor import (
     install_reactor,
@@ -109,10 +109,9 @@ class Crawler:
         lf_cls: Type[LogFormatter] = load_object(self.settings["LOG_FORMATTER"])
         self.logformatter = lf_cls.from_crawler(self)
 
-        self.request_fingerprinter = create_instance(
+        self.request_fingerprinter = build_from_crawler(
             load_object(self.settings["REQUEST_FINGERPRINTER_CLASS"]),
-            settings=self.settings,
-            crawler=self,
+            self,
         )
 
         reactor_class: str = self.settings["TWISTED_REACTOR"]
@@ -404,7 +403,7 @@ class CrawlerProcess(CrawlerRunner):
             d.addBoth(self._stop_reactor)
 
         resolver_class = load_object(self.settings["DNS_RESOLVER"])
-        resolver = create_instance(resolver_class, self.settings, self, reactor=reactor)
+        resolver = build_from_crawler(resolver_class, self, reactor=reactor)
         resolver.install_on_reactor()
         tp = reactor.getThreadPool()
         tp.adjustPoolsize(maxthreads=self.settings.getint("REACTOR_THREADPOOL_MAXSIZE"))
diff --git a/scrapy/extensions/feedexport.py b/scrapy/extensions/feedexport.py
index fadbbb582..e5e363b52 100644
--- a/scrapy/extensions/feedexport.py
+++ b/scrapy/extensions/feedexport.py
@@ -28,7 +28,7 @@ from scrapy.utils.defer import maybe_deferred_to_future
 from scrapy.utils.deprecate import create_deprecated_class
 from scrapy.utils.ftp import ftp_store_file
 from scrapy.utils.log import failure_to_exc_info
-from scrapy.utils.misc import create_instance, load_object
+from scrapy.utils.misc import build_from_crawler, load_object
 from scrapy.utils.python import without_none_values
 
 logger = logging.getLogger(__name__)
@@ -371,7 +371,7 @@ class FeedSlot:
             self._exporting = True
 
     def _get_instance(self, objcls, *args, **kwargs):
-        return create_instance(objcls, self.settings, self.crawler, *args, **kwargs)
+        return build_from_crawler(objcls, self.crawler, *args, **kwargs)
 
     def _get_exporter(self, file, format, *args, **kwargs):
         return self._get_instance(self.exporters[format], file, *args, **kwargs)
diff --git a/scrapy/middleware.py b/scrapy/middleware.py
index 090588130..f60c726f9 100644
--- a/scrapy/middleware.py
+++ b/scrapy/middleware.py
@@ -23,7 +23,7 @@ from scrapy import Spider
 from scrapy.exceptions import NotConfigured
 from scrapy.settings import Settings
 from scrapy.utils.defer import process_chain, process_parallel
-from scrapy.utils.misc import create_instance, load_object
+from scrapy.utils.misc import build_from_crawler, build_from_settings, load_object
 
 if TYPE_CHECKING:
     # typing.Self requires Python 3.11
@@ -64,7 +64,10 @@ class MiddlewareManager:
         for clspath in mwlist:
             try:
                 mwcls = load_object(clspath)
-                mw = create_instance(mwcls, settings, crawler)
+                if crawler is not None:
+                    mw = build_from_crawler(mwcls, crawler)
+                else:
+                    mw = build_from_settings(mwcls, settings)
                 middlewares.append(mw)
                 enabled.append(clspath)
             except NotConfigured as e:
diff --git a/scrapy/pqueues.py b/scrapy/pqueues.py
index 62a9af477..b62d2fe58 100644
--- a/scrapy/pqueues.py
+++ b/scrapy/pqueues.py
@@ -1,7 +1,7 @@
 import hashlib
 import logging
 
-from scrapy.utils.misc import create_instance
+from scrapy.utils.misc import build_from_crawler
 
 logger = logging.getLogger(__name__)
 
@@ -72,9 +72,8 @@ class ScrapyPriorityQueue:
         self.curprio = min(startprios)
 
     def qfactory(self, key):
-        return create_instance(
+        return build_from_crawler(
             self.downstream_queue_cls,
-            None,
             self.crawler,
             self.key + "/" + str(key),
         )
diff --git a/scrapy/utils/misc.py b/scrapy/utils/misc.py
index a9364bea2..b38190cb3 100644
--- a/scrapy/utils/misc.py
+++ b/scrapy/utils/misc.py
@@ -25,6 +25,7 @@ from typing import (
     cast,
 )
 
+from scrapy.exceptions import ScrapyDeprecationWarning
 from scrapy.item import Item
 from scrapy.utils.datatypes import LocalWeakReferencedCache
 
@@ -142,6 +143,13 @@ def create_instance(objcls, settings, crawler, *args, **kwargs):
        Raises ``TypeError`` if the resulting instance is ``None`` (e.g. if an
        extension has not been implemented correctly).
     """
+    warnings.warn(
+        "The create_instance() function is deprecated. "
+        "Please use build_from_crawler() or build_from_settings() instead.",
+        category=ScrapyDeprecationWarning,
+        stacklevel=2,
+    )
+
     if settings is None:
         if crawler is None:
             raise ValueError("Specify at least one of settings and crawler.")
@@ -160,6 +168,45 @@ def create_instance(objcls, settings, crawler, *args, **kwargs):
     return instance
 
 
+def build_from_crawler(objcls, crawler, /, *args, **kwargs):
+    """Construct a class instance using its ``from_crawler`` constructor.
+
+    ``*args`` and ``**kwargs`` are forwarded to the constructor.
+
+    Raises ``TypeError`` if the resulting instance is ``None``.
+    """
+    if hasattr(objcls, "from_crawler"):
+        instance = objcls.from_crawler(crawler, *args, **kwargs)
+        method_name = "from_crawler"
+    elif hasattr(objcls, "from_settings"):
+        instance = objcls.from_settings(crawler.settings, *args, **kwargs)
+        method_name = "from_settings"
+    else:
+        instance = objcls(*args, **kwargs)
+        method_name = "__new__"
+    if instance is None:
+        raise TypeError(f"{objcls.__qualname__}.{method_name} returned None")
+    return instance
+
+
+def build_from_settings(objcls, settings, /, *args, **kwargs):
+    """Construct a class instance using its ``from_settings`` constructor.
+
+    ``*args`` and ``**kwargs`` are forwarded to the constructor.
+
+    Raises ``TypeError`` if the resulting instance is ``None``.
+    """
+    if hasattr(objcls, "from_settings"):
+        instance = objcls.from_settings(settings, *args, **kwargs)
+        method_name = "from_settings"
+    else:
+        instance = objcls(*args, **kwargs)
+        method_name = "__new__"
+    if instance is None:
+        raise TypeError(f"{objcls.__qualname__}.{method_name} returned None")
+    return instance
+
+
 @contextmanager
 def set_environ(**kwargs: str) -> Generator[None, Any, None]:
     """Temporarily set environment variables inside the context manager and


Test patch:
diff --git a/tests/test_addons.py b/tests/test_addons.py
index 0f4f2e5b8..f1b01bc5c 100644
--- a/tests/test_addons.py
+++ b/tests/test_addons.py
@@ -89,7 +89,7 @@ class AddonManagerTest(unittest.TestCase):
             self.assertEqual([a.number for a in manager.addons], expected_order)
             self.assertEqual(crawler.settings.getint("KEY1"), expected_order[-1])
 
-    def test_create_instance(self):
+    def test_build_from_crawler(self):
         settings_dict = {
             "ADDONS": {"tests.test_addons.CreateInstanceAddon": 0},
             "MYADDON": {"MYADDON_KEY": "val"},
@@ -167,12 +167,12 @@ class AddonManagerTest(unittest.TestCase):
                 pass
 
         with patch("scrapy.addons.logger") as logger_mock:
-            with patch("scrapy.addons.create_instance") as create_instance_mock:
+            with patch("scrapy.addons.build_from_crawler") as build_from_crawler_mock:
                 settings_dict = {
                     "ADDONS": {LoggedAddon: 1},
                 }
                 addon = LoggedAddon()
-                create_instance_mock.return_value = addon
+                build_from_crawler_mock.return_value = addon
                 crawler = get_crawler(settings_dict=settings_dict)
                 logger_mock.info.assert_called_once_with(
                     "Enabled addons:\n%(addons)s",
diff --git a/tests/test_downloader_handlers.py b/tests/test_downloader_handlers.py
index 924ece6f9..dd07d33f1 100644
--- a/tests/test_downloader_handlers.py
+++ b/tests/test_downloader_handlers.py
@@ -29,7 +29,7 @@ from scrapy.http import Headers, HtmlResponse, Request
 from scrapy.http.response.text import TextResponse
 from scrapy.responsetypes import responsetypes
 from scrapy.spiders import Spider
-from scrapy.utils.misc import create_instance
+from scrapy.utils.misc import build_from_crawler
 from scrapy.utils.python import to_bytes
 from scrapy.utils.test import get_crawler, skip_if_no_boto
 from tests import NON_EXISTING_RESOLVABLE
@@ -109,7 +109,7 @@ class FileTestCase(unittest.TestCase):
         # add a special char to check that they are handled correctly
         self.tmpname = Path(self.mktemp() + "^")
         Path(self.tmpname).write_text("0123456789", encoding="utf-8")
-        handler = create_instance(FileDownloadHandler, None, get_crawler())
+        handler = build_from_crawler(FileDownloadHandler, get_crawler())
         self.download_request = handler.download_request
 
     def tearDown(self):
@@ -257,8 +257,8 @@ class HttpTestCase(unittest.TestCase):
         else:
             self.port = reactor.listenTCP(0, self.wrapper, interface=self.host)
         self.portno = self.port.getHost().port
-        self.download_handler = create_instance(
-            self.download_handler_cls, None, get_crawler()
+        self.download_handler = build_from_crawler(
+            self.download_handler_cls, get_crawler()
         )
         self.download_request = self.download_handler.download_request
 
@@ -557,7 +557,7 @@ class Http11TestCase(HttpTestCase):
 
     def test_download_broken_content_allow_data_loss_via_setting(self, url="broken"):
         crawler = get_crawler(settings_dict={"DOWNLOAD_FAIL_ON_DATALOSS": False})
-        download_handler = create_instance(self.download_handler_cls, None, crawler)
+        download_handler = build_from_crawler(self.download_handler_cls, crawler)
         request = Request(self.getURL(url))
         d = download_handler.download_request(request, Spider("foo"))
         d.addCallback(lambda r: r.flags)
@@ -590,7 +590,7 @@ class Https11TestCase(Http11TestCase):
         crawler = get_crawler(
             settings_dict={"DOWNLOADER_CLIENT_TLS_VERBOSE_LOGGING": True}
         )
-        download_handler = create_instance(self.download_handler_cls, None, crawler)
+        download_handler = build_from_crawler(self.download_handler_cls, crawler)
         try:
             with LogCapture() as log_capture:
                 request = Request(self.getURL("file"))
@@ -669,9 +669,7 @@ class Https11CustomCiphers(unittest.TestCase):
         crawler = get_crawler(
             settings_dict={"DOWNLOADER_CLIENT_TLS_CIPHERS": "CAMELLIA256-SHA"}
         )
-        self.download_handler = create_instance(
-            self.download_handler_cls, None, crawler
-        )
+        self.download_handler = build_from_crawler(self.download_handler_cls, crawler)
         self.download_request = self.download_handler.download_request
 
     @defer.inlineCallbacks
@@ -751,8 +749,8 @@ class HttpProxyTestCase(unittest.TestCase):
         wrapper = WrappingFactory(site)
         self.port = reactor.listenTCP(0, wrapper, interface="127.0.0.1")
         self.portno = self.port.getHost().port
-        self.download_handler = create_instance(
-            self.download_handler_cls, None, get_crawler()
+        self.download_handler = build_from_crawler(
+            self.download_handler_cls, get_crawler()
         )
         self.download_request = self.download_handler.download_request
 
@@ -830,10 +828,9 @@ class S3AnonTestCase(unittest.TestCase):
     def setUp(self):
         skip_if_no_boto()
         crawler = get_crawler()
-        self.s3reqh = create_instance(
-            objcls=S3DownloadHandler,
-            settings=None,
-            crawler=crawler,
+        self.s3reqh = build_from_crawler(
+            S3DownloadHandler,
+            crawler,
             httpdownloadhandler=HttpDownloadHandlerMock,
             # anon=True, # implicit
         )
@@ -861,10 +858,9 @@ class S3TestCase(unittest.TestCase):
     def setUp(self):
         skip_if_no_boto()
         crawler = get_crawler()
-        s3reqh = create_instance(
-            objcls=S3DownloadHandler,
-            settings=None,
-            crawler=crawler,
+        s3reqh = build_from_crawler(
+            S3DownloadHandler,
+            crawler,
             aws_access_key_id=self.AWS_ACCESS_KEY_ID,
             aws_secret_access_key=self.AWS_SECRET_ACCESS_KEY,
             httpdownloadhandler=HttpDownloadHandlerMock,
@@ -889,10 +885,9 @@ class S3TestCase(unittest.TestCase):
     def test_extra_kw(self):
         try:
             crawler = get_crawler()
-            create_instance(
-                objcls=S3DownloadHandler,
-                settings=None,
-                crawler=crawler,
+            build_from_crawler(
+                S3DownloadHandler,
+                crawler,
                 extra_kw=True,
             )
         except Exception as e:
@@ -1039,9 +1034,7 @@ class BaseFTPTestCase(unittest.TestCase):
         self.port = reactor.listenTCP(0, self.factory, interface="127.0.0.1")
         self.portNum = self.port.getHost().port
         crawler = get_crawler()
-        self.download_handler = create_instance(
-            FTPDownloadHandler, crawler.settings, crawler
-        )
+        self.download_handler = build_from_crawler(FTPDownloadHandler, crawler)
         self.addCleanup(self.port.stopListening)
 
     def tearDown(self):
@@ -1185,9 +1178,7 @@ class AnonymousFTPTestCase(BaseFTPTestCase):
         self.port = reactor.listenTCP(0, self.factory, interface="127.0.0.1")
         self.portNum = self.port.getHost().port
         crawler = get_crawler()
-        self.download_handler = create_instance(
-            FTPDownloadHandler, crawler.settings, crawler
-        )
+        self.download_handler = build_from_crawler(FTPDownloadHandler, crawler)
         self.addCleanup(self.port.stopListening)
 
     def tearDown(self):
@@ -1197,9 +1188,7 @@ class AnonymousFTPTestCase(BaseFTPTestCase):
 class DataURITestCase(unittest.TestCase):
     def setUp(self):
         crawler = get_crawler()
-        self.download_handler = create_instance(
-            DataURIDownloadHandler, crawler.settings, crawler
-        )
+        self.download_handler = build_from_crawler(DataURIDownloadHandler, crawler)
         self.download_request = self.download_handler.download_request
         self.spider = Spider("foo")
 
diff --git a/tests/test_downloader_handlers_http2.py b/tests/test_downloader_handlers_http2.py
index 31fa1430d..322075043 100644
--- a/tests/test_downloader_handlers_http2.py
+++ b/tests/test_downloader_handlers_http2.py
@@ -11,7 +11,7 @@ from twisted.web.http import H2_ENABLED
 
 from scrapy.http import Request
 from scrapy.spiders import Spider
-from scrapy.utils.misc import create_instance
+from scrapy.utils.misc import build_from_crawler
 from scrapy.utils.test import get_crawler
 from tests.mockserver import ssl_context_factory
 from tests.test_downloader_handlers import (
@@ -240,8 +240,8 @@ class Https2ProxyTestCase(Http11ProxyTestCase):
             interface=self.host,
         )
         self.portno = self.port.getHost().port
-        self.download_handler = create_instance(
-            self.download_handler_cls, None, get_crawler()
+        self.download_handler = build_from_crawler(
+            self.download_handler_cls, get_crawler()
         )
         self.download_request = self.download_handler.download_request
 
diff --git a/tests/test_settings/__init__.py b/tests/test_settings/__init__.py
index e7799737f..3fde5e8c5 100644
--- a/tests/test_settings/__init__.py
+++ b/tests/test_settings/__init__.py
@@ -440,7 +440,7 @@ class SettingsTest(unittest.TestCase):
 
     def test_passing_objects_as_values(self):
         from scrapy.core.downloader.handlers.file import FileDownloadHandler
-        from scrapy.utils.misc import create_instance
+        from scrapy.utils.misc import build_from_crawler
         from scrapy.utils.test import get_crawler
 
         class TestPipeline:
@@ -468,7 +468,7 @@ class SettingsTest(unittest.TestCase):
 
         myhandler = settings.getdict("DOWNLOAD_HANDLERS").pop("ftp")
         self.assertEqual(myhandler, FileDownloadHandler)
-        myhandler_instance = create_instance(myhandler, None, get_crawler())
+        myhandler_instance = build_from_crawler(myhandler, get_crawler())
         self.assertIsInstance(myhandler_instance, FileDownloadHandler)
         self.assertTrue(hasattr(myhandler_instance, "download_request"))
 
diff --git a/tests/test_utils_misc/__init__.py b/tests/test_utils_misc/__init__.py
index 69793ee75..ee3314d8e 100644
--- a/tests/test_utils_misc/__init__.py
+++ b/tests/test_utils_misc/__init__.py
@@ -7,6 +7,8 @@ from unittest import mock
 from scrapy.item import Field, Item
 from scrapy.utils.misc import (
     arg_to_iter,
+    build_from_crawler,
+    build_from_settings,
     create_instance,
     load_object,
     rel_has_nofollow,
@@ -153,6 +155,78 @@ class UtilsMiscTestCase(unittest.TestCase):
         with self.assertRaises(TypeError):
             create_instance(m, settings, None)
 
+    def test_build_from_crawler(self):
+        settings = mock.MagicMock()
+        crawler = mock.MagicMock(spec_set=["settings"])
+        args = (True, 100.0)
+        kwargs = {"key": "val"}
+
+        def _test_with_crawler(mock, settings, crawler):
+            build_from_crawler(mock, crawler, *args, **kwargs)
+            if hasattr(mock, "from_crawler"):
+                mock.from_crawler.assert_called_once_with(crawler, *args, **kwargs)
+                if hasattr(mock, "from_settings"):
+                    self.assertEqual(mock.from_settings.call_count, 0)
+                self.assertEqual(mock.call_count, 0)
+            elif hasattr(mock, "from_settings"):
+                mock.from_settings.assert_called_once_with(settings, *args, **kwargs)
+                self.assertEqual(mock.call_count, 0)
+            else:
+                mock.assert_called_once_with(*args, **kwargs)
+
+        # Check usage of correct constructor using three mocks:
+        #   1. with no alternative constructors
+        #   2. with from_crawler() constructor
+        #   3. with from_settings() and from_crawler() constructor
+        spec_sets = (
+            ["__qualname__"],
+            ["__qualname__", "from_crawler"],
+            ["__qualname__", "from_settings", "from_crawler"],
+        )
+        for specs in spec_sets:
+            m = mock.MagicMock(spec_set=specs)
+            _test_with_crawler(m, settings, crawler)
+            m.reset_mock()
+
+        # Check adoption of crawler
+        m = mock.MagicMock(spec_set=["__qualname__", "from_crawler"])
+        m.from_crawler.return_value = None
+        with self.assertRaises(TypeError):
+            build_from_crawler(m, crawler, *args, **kwargs)
+
+    def test_build_from_settings(self):
+        settings = mock.MagicMock()
+        args = (True, 100.0)
+        kwargs = {"key": "val"}
+
+        def _test_with_settings(mock, settings):
+            build_from_settings(mock, settings, *args, **kwargs)
+            if hasattr(mock, "from_settings"):
+                mock.from_settings.assert_called_once_with(settings, *args, **kwargs)
+                self.assertEqual(mock.call_count, 0)
+            else:
+                mock.assert_called_once_with(*args, **kwargs)
+
+        # Check usage of correct constructor using three mocks:
+        #   1. with no alternative constructors
+        #   2. with from_settings() constructor
+        #   3. with from_settings() and from_crawler() constructor
+        spec_sets = (
+            ["__qualname__"],
+            ["__qualname__", "from_settings"],
+            ["__qualname__", "from_settings", "from_crawler"],
+        )
+        for specs in spec_sets:
+            m = mock.MagicMock(spec_set=specs)
+            _test_with_settings(m, settings)
+            m.reset_mock()
+
+        # Check adoption of crawler settings
+        m = mock.MagicMock(spec_set=["__qualname__", "from_settings"])
+        m.from_settings.return_value = None
+        with self.assertRaises(TypeError):
+            build_from_settings(m, settings, *args, **kwargs)
+
     def test_set_environ(self):
         assert os.environ.get("some_test_environ") is None
         with set_environ(some_test_environ="test_value"):
diff --git a/tests/test_webclient.py b/tests/test_webclient.py
index 0042fe8f0..d4b6ba15b 100644
--- a/tests/test_webclient.py
+++ b/tests/test_webclient.py
@@ -24,7 +24,7 @@ from scrapy.core.downloader import webclient as client
 from scrapy.core.downloader.contextfactory import ScrapyClientContextFactory
 from scrapy.http import Headers, Request
 from scrapy.settings import Settings
-from scrapy.utils.misc import create_instance
+from scrapy.utils.misc import build_from_settings
 from scrapy.utils.python import to_bytes, to_unicode
 from tests.mockserver import (
     BrokenDownloadResource,
@@ -470,8 +470,8 @@ class WebClientCustomCiphersSSLTestCase(WebClientSSLTestCase):
     def testPayload(self):
         s = "0123456789" * 10
         settings = Settings({"DOWNLOADER_CLIENT_TLS_CIPHERS": self.custom_ciphers})
-        client_context_factory = create_instance(
-            ScrapyClientContextFactory, settings=settings, crawler=None
+        client_context_factory = build_from_settings(
+            ScrapyClientContextFactory, settings
         )
         return getPage(
             self.getURL("payload"), body=s, contextFactory=client_context_factory
@@ -482,8 +482,8 @@ class WebClientCustomCiphersSSLTestCase(WebClientSSLTestCase):
         settings = Settings(
             {"DOWNLOADER_CLIENT_TLS_CIPHERS": "ECDHE-RSA-AES256-GCM-SHA384"}
         )
-        client_context_factory = create_instance(
-            ScrapyClientContextFactory, settings=settings, crawler=None
+        client_context_factory = build_from_settings(
+            ScrapyClientContextFactory, settings
         )
         d = getPage(
             self.getURL("payload"), body=s, contextFactory=client_context_factory