scrapy/tests/test_downloadermiddleware_httpcache.py

from __future__ import annotations

import email.utils
import gc
import logging
import shutil
import tempfile
import time
from contextlib import contextmanager
from pathlib import Path
from typing import TYPE_CHECKING, Any
from unittest import mock

import pytest
from twisted.internet.defer import Deferred

from scrapy import signals
from scrapy.core.downloader.middleware import DownloaderMiddlewareManager
from scrapy.downloadermiddlewares.httpcache import HttpCacheMiddleware
from scrapy.exceptions import IgnoreRequest
from scrapy.extensions.httpcache import DummyPolicy
from scrapy.http import HtmlResponse, Request, Response
from scrapy.spiders import Spider
from scrapy.utils.defer import (
    _defer_sleep_async,
    deferred_from_coro,
    maybe_deferred_to_future,
)
from scrapy.utils.test import get_crawler
from tests.utils.decorators import coroutine_test

if TYPE_CHECKING:
    from collections.abc import Callable, Generator

    from scrapy.crawler import Crawler


class AlwaysStalePolicy(DummyPolicy):
    """:class:`~scrapy.extensions.httpcache.DummyPolicy` that always
    revalidates cached responses."""

    def is_cached_response_fresh(self, cachedresponse, request):
        return False


class TestBase:
    """Base class with common setup and helper methods."""

    policy_class: str
    storage_class: str

    def setup_method(self):
        self.yesterday = email.utils.formatdate(time.time() - 86400)
        self.today = email.utils.formatdate()
        self.tomorrow = email.utils.formatdate(time.time() + 86400)
        self.tmpdir = tempfile.mkdtemp()
        self.request = Request("http://www.example.com", headers={"User-Agent": "test"})
        self.response = Response(
            "http://www.example.com",
            headers={"Content-Type": "text/html"},
            body=b"test body",
            status=202,
        )

    def teardown_method(self):
        shutil.rmtree(self.tmpdir)

    def _get_settings(self, **new_settings: Any) -> dict[str, Any]:
        settings = {
            "HTTPCACHE_ENABLED": True,
            "HTTPCACHE_DIR": self.tmpdir,
            "HTTPCACHE_IGNORE_HTTP_CODES": [],
            "HTTPCACHE_POLICY": self.policy_class,
            "HTTPCACHE_STORAGE": self.storage_class,
        }
        settings.update(new_settings)
        return settings

    @contextmanager
    def _get_crawler(self, **new_settings: Any) -> Generator[Crawler]:
        settings = self._get_settings(**new_settings)
        crawler = get_crawler(Spider, settings)
        crawler.spider = crawler._create_spider("example.com")
        assert crawler.stats
        crawler.stats.open_spider()
        try:
            yield crawler
        finally:
            crawler.stats.close_spider()

    @contextmanager
    def _storage(self, **new_settings: Any):
        with self._middleware(**new_settings) as mw:
            yield mw.storage, mw.crawler

    @contextmanager
    def _middleware(self, **new_settings: Any) -> Generator[HttpCacheMiddleware]:
        with self._get_crawler(**new_settings) as crawler:
            assert crawler.spider
            mw = HttpCacheMiddleware.from_crawler(crawler)
            mw.spider_opened(crawler.spider)
            try:
                yield mw
            finally:
                mw.spider_closed(crawler.spider)

    def assertEqualResponse(self, response1: Response, response2: Response) -> None:
        assert response1.url == response2.url
        assert response1.status == response2.status
        assert response1.headers == response2.headers
        assert response1.body == response2.body


class StorageTestMixin(TestBase):
    """Mixin containing storage-specific test methods."""

    def _corrupt_cache_entry(
        self, storage: Any, spider: Spider, request: Request
    ) -> None:
        """Make the cache entry of *request* unreadable for *storage*."""
        raise NotImplementedError

    def test_storage(self):
        with self._storage(HTTPCACHE_EXPIRATION_SECS=1) as (storage, crawler):
            request2 = self.request.copy()
            assert storage.retrieve_response(crawler.spider, request2) is None

            storage.store_response(crawler.spider, self.request, self.response)
            response2 = storage.retrieve_response(crawler.spider, request2)
            assert isinstance(response2, HtmlResponse)  # content-type header
            self.assertEqualResponse(self.response, response2)

            expired = time.time() + storage.expiration_secs + 1
            with mock.patch("scrapy.extensions.httpcache.time", return_value=expired):
                assert storage.retrieve_response(crawler.spider, request2) is None

    def test_storage_never_expire(self):
        with self._storage(HTTPCACHE_EXPIRATION_SECS=0) as (storage, crawler):
            assert storage.retrieve_response(crawler.spider, self.request) is None
            storage.store_response(crawler.spider, self.request, self.response)
            future = time.time() + 10**6
            with mock.patch("scrapy.extensions.httpcache.time", return_value=future):
                assert storage.retrieve_response(crawler.spider, self.request)

    @coroutine_test
    async def test_corrupted_cache_entry_is_a_miss(self, caplog):
        with self._middleware() as mw:
            spider = mw.crawler.spider
            assert spider
            assert mw.crawler.stats
            mw.storage.store_response(spider, self.request, self.response)
            self._corrupt_cache_entry(mw.storage, spider, self.request)

            caplog.clear()
            with caplog.at_level(logging.WARNING):
                assert await mw.process_request(self.request) is None

            assert "treating it as a cache miss" in caplog.text
            assert mw.crawler.stats.get_value("httpcache/retrieve_error") == 1
            assert mw.crawler.stats.get_value("httpcache/miss") == 1

            # Storing the response again replaces the corrupted cache entry.
            mw.storage.store_response(spider, self.request, self.response)
            self.assertEqualResponse(
                self.response, mw.storage.retrieve_response(spider, self.request)
            )

    @coroutine_test
    async def test_corrupted_cache_entry_ignore_missing(self):
        with self._middleware(HTTPCACHE_IGNORE_MISSING=True) as mw:
            spider = mw.crawler.spider
            assert spider
            assert mw.crawler.stats
            mw.storage.store_response(spider, self.request, self.response)
            self._corrupt_cache_entry(mw.storage, spider, self.request)

            with pytest.raises(IgnoreRequest):
                await mw.process_request(self.request)

            assert mw.crawler.stats.get_value("httpcache/retrieve_error") == 1
            assert mw.crawler.stats.get_value("httpcache/ignore") == 1

    def test_storage_no_content_type_header(self):
        """Test that the response body is used to get the right response class
        even if there is no Content-Type header"""
        with self._storage() as (storage, crawler):
            assert storage.retrieve_response(crawler.spider, self.request) is None
            response = Response(
                "http://www.example.com",
                body=b"<!DOCTYPE html>\n<title>.</title>",
                status=202,
            )
            storage.store_response(crawler.spider, self.request, response)
            cached_response = storage.retrieve_response(crawler.spider, self.request)
            assert isinstance(cached_response, HtmlResponse)
            self.assertEqualResponse(response, cached_response)


class PolicyTestMixin(TestBase):
    """Mixin containing policy-specific test methods."""

    @coroutine_test
    async def test_dont_cache(self):
        with self._middleware() as mw:
            self.request.meta["dont_cache"] = True
            assert await mw.process_request(self.request) is None
            mw.process_response(self.request, self.response)
            assert mw.storage.retrieve_response(mw.crawler.spider, self.request) is None

        with self._middleware() as mw:
            self.request.meta["dont_cache"] = False
            mw.process_response(self.request, self.response)
            if mw.policy.should_cache_response(self.response, self.request):
                assert isinstance(
                    mw.storage.retrieve_response(mw.crawler.spider, self.request),
                    self.response.__class__,
                )


class DummyPolicyTestMixin(PolicyTestMixin):
    """Mixin containing dummy policy specific test methods."""

    @coroutine_test
    async def test_middleware(self):
        with self._middleware() as mw:
            assert await mw.process_request(self.request) is None
            mw.process_response(self.request, self.response)
            response = await mw.process_request(self.request)
            assert isinstance(response, HtmlResponse)
            self.assertEqualResponse(self.response, response)
            assert "cached" in response.flags

    @coroutine_test
    async def test_different_request_response_urls(self):
        with self._middleware() as mw:
            req = Request("http://host.com/path")
            res = Response("http://host2.net/test.html")
            assert await mw.process_request(req) is None
            mw.process_response(req, res)
            cached = await mw.process_request(req)
            assert isinstance(cached, Response)
            self.assertEqualResponse(res, cached)
            assert "cached" in cached.flags

    @coroutine_test
    async def test_middleware_ignore_missing(self):
        with self._middleware(HTTPCACHE_IGNORE_MISSING=True) as mw:
            with pytest.raises(IgnoreRequest):
                await mw.process_request(self.request)
            mw.process_response(self.request, self.response)
            response = await mw.process_request(self.request)
            assert isinstance(response, HtmlResponse)
            self.assertEqualResponse(self.response, response)
            assert "cached" in response.flags

    @coroutine_test
    async def test_middleware_ignore_schemes(self):
        # http responses are cached by default
        req, res = Request("http://test.com/"), Response("http://test.com/")
        with self._middleware() as mw:
            assert await mw.process_request(req) is None
            mw.process_response(req, res)

            cached = await mw.process_request(req)
            assert isinstance(cached, Response), type(cached)
            self.assertEqualResponse(res, cached)
            assert "cached" in cached.flags

        # file response is not cached by default
        req, res = Request("file:///tmp/t.txt"), Response("file:///tmp/t.txt")
        with self._middleware() as mw:
            assert await mw.process_request(req) is None
            mw.process_response(req, res)

            assert mw.storage.retrieve_response(mw.crawler.spider, req) is None
            assert await mw.process_request(req) is None

        # s3 scheme response is cached by default
        req, res = Request("s3://bucket/key"), Response("s3://bucket/key")
        with self._middleware() as mw:
            assert await mw.process_request(req) is None
            mw.process_response(req, res)

            cached = await mw.process_request(req)
            assert isinstance(cached, Response), type(cached)
            self.assertEqualResponse(res, cached)
            assert "cached" in cached.flags

        # ignore s3 scheme
        req, res = Request("s3://bucket/key2"), Response("s3://bucket/key2")
        with self._middleware(HTTPCACHE_IGNORE_SCHEMES=["s3"]) as mw:
            assert await mw.process_request(req) is None
            mw.process_response(req, res)

            assert mw.storage.retrieve_response(mw.crawler.spider, req) is None
            assert await mw.process_request(req) is None

    @coroutine_test
    async def test_middleware_ignore_http_codes(self):
        # test response is not cached
        with self._middleware(HTTPCACHE_IGNORE_HTTP_CODES=[202]) as mw:
            assert await mw.process_request(self.request) is None
            mw.process_response(self.request, self.response)

            assert mw.storage.retrieve_response(mw.crawler.spider, self.request) is None
            assert await mw.process_request(self.request) is None

        # test response is cached
        with self._middleware(HTTPCACHE_IGNORE_HTTP_CODES=[203]) as mw:
            mw.process_response(self.request, self.response)
            response = await mw.process_request(self.request)
            assert isinstance(response, HtmlResponse)
            self.assertEqualResponse(self.response, response)
            assert "cached" in response.flags

    @coroutine_test
    async def test_revalidation_keeps_cached_response(self):
        # The dummy policy considers every cached response valid, so a policy
        # that subclasses it to force revalidation always gets the cached
        # response back, whatever the new response is.
        with self._middleware(HTTPCACHE_POLICY=AlwaysStalePolicy) as mw:
            assert await mw.process_request(self.request) is None
            mw.process_response(self.request, self.response)

            assert await mw.process_request(self.request) is None
            fresh_response = self.response.replace(body=b"new body")
            response = mw.process_response(self.request, fresh_response)
            assert isinstance(response, Response)
            self.assertEqualResponse(self.response, response)
            assert "cached" in response.flags
            assert mw.stats.get_value("httpcache/revalidate") == 1


class RFC2616PolicyTestMixin(PolicyTestMixin):
    """Mixin containing RFC2616 policy specific test methods."""

    @staticmethod
    async def _process_requestresponse(
        mw: HttpCacheMiddleware, request: Request, response: Response | None
    ) -> Response:
        result: Request | Response | None = None
        try:
            result = await mw.process_request(request)
            if result:
                assert isinstance(result, Response)
                return result
            assert response is not None
            result = mw.process_response(request, response)
            assert isinstance(result, Response)
            return result
        except Exception:
            print("Request", request)
            print("Response", response)
            print("Result", result)
            raise

    @coroutine_test
    async def test_request_cacheability(self):
        res0 = Response(
            self.request.url, status=200, headers={"Expires": self.tomorrow}
        )
        req0 = Request("http://example.com")
        req1 = req0.replace(headers={"Cache-Control": "no-store"})
        req2 = req0.replace(headers={"Cache-Control": "no-cache"})
        with self._middleware() as mw:
            # response for a request with no-store must not be cached
            res1 = await self._process_requestresponse(mw, req1, res0)
            self.assertEqualResponse(res1, res0)
            assert mw.storage.retrieve_response(mw.crawler.spider, req1) is None
            # Re-do request without no-store and expect it to be cached
            res2 = await self._process_requestresponse(mw, req0, res0)
            assert "cached" not in res2.flags
            res3 = await mw.process_request(req0)
            assert isinstance(res3, Response)
            assert "cached" in res3.flags
            self.assertEqualResponse(res2, res3)
            # request with no-cache directive must not return cached response
            # but it allows new response to be stored
            res0b = res0.replace(body=b"foo")
            res4 = await self._process_requestresponse(mw, req2, res0b)
            self.assertEqualResponse(res4, res0b)
            assert "cached" not in res4.flags
            res5 = await self._process_requestresponse(mw, req0, None)
            self.assertEqualResponse(res5, res0b)
            assert "cached" in res5.flags

    @coroutine_test
    async def test_response_cacheability(self):
        responses = [
            # 304 is not cacheable no matter what servers sends
            (False, 304, {}),
            (False, 304, {"Last-Modified": self.yesterday}),
            (False, 304, {"Expires": self.tomorrow}),
            (False, 304, {"Etag": "bar"}),
            (False, 304, {"Cache-Control": "max-age=3600"}),
            # Always obey no-store cache control
            (False, 200, {"Cache-Control": "no-store"}),
            (False, 200, {"Cache-Control": "no-store, max-age=300"}),  # invalid
            (
                False,
                200,
                {"Cache-Control": "no-store", "Expires": self.tomorrow},
            ),  # invalid
            # Ignore responses missing expiration and/or validation headers
            (False, 200, {}),
            (False, 302, {}),
            (False, 307, {}),
            (False, 404, {}),
            # Cache responses with expiration and/or validation headers
            (True, 200, {"Last-Modified": self.yesterday}),
            (True, 203, {"Last-Modified": self.yesterday}),
            (True, 300, {"Last-Modified": self.yesterday}),
            (True, 301, {"Last-Modified": self.yesterday}),
            (True, 308, {"Last-Modified": self.yesterday}),
            (True, 401, {"Last-Modified": self.yesterday}),
            (True, 404, {"Cache-Control": "public, max-age=600"}),
            (True, 302, {"Expires": self.tomorrow}),
            (True, 200, {"Etag": "foo"}),
        ]
        with self._middleware() as mw:
            for idx, (shouldcache, status, headers) in enumerate(responses):
                req0 = Request(f"http://example-{idx}.com")
                res0 = Response(req0.url, status=status, headers=headers)
                res1 = await self._process_requestresponse(mw, req0, res0)
                res304 = res0.replace(status=304)
                res2 = await self._process_requestresponse(
                    mw, req0, res304 if shouldcache else res0
                )
                self.assertEqualResponse(res1, res0)
                self.assertEqualResponse(res2, res0)
                resc = mw.storage.retrieve_response(mw.crawler.spider, req0)
                if shouldcache:
                    self.assertEqualResponse(resc, res1)
                    assert "cached" in res2.flags
                    assert res2.status != 304
                else:
                    assert not resc
                    assert "cached" not in res2.flags

        # cache unconditionally unless response contains no-store or is a 304
        with self._middleware(HTTPCACHE_ALWAYS_STORE=True) as mw:
            for idx, (_, status, headers) in enumerate(responses):
                shouldcache = (
                    "no-store" not in headers.get("Cache-Control", "") and status != 304
                )
                req0 = Request(f"http://example2-{idx}.com")
                res0 = Response(req0.url, status=status, headers=headers)
                res1 = await self._process_requestresponse(mw, req0, res0)
                res304 = res0.replace(status=304)
                res2 = await self._process_requestresponse(
                    mw, req0, res304 if shouldcache else res0
                )
                self.assertEqualResponse(res1, res0)
                self.assertEqualResponse(res2, res0)
                resc = mw.storage.retrieve_response(mw.crawler.spider, req0)
                if shouldcache:
                    self.assertEqualResponse(resc, res1)
                    assert "cached" in res2.flags
                    assert res2.status != 304
                else:
                    assert not resc
                    assert "cached" not in res2.flags

    @coroutine_test
    async def test_cached_and_fresh(self):
        sampledata = [
            (200, {"Date": self.yesterday, "Expires": self.tomorrow}),
            (200, {"Date": self.yesterday, "Cache-Control": "max-age=86405"}),
            (200, {"Age": "299", "Cache-Control": "max-age=300"}),
            # Obey max-age if present over any others
            (
                200,
                {
                    "Date": self.today,
                    "Age": "86405",
                    "Cache-Control": "max-age=" + str(86400 * 3),
                    "Expires": self.yesterday,
                    "Last-Modified": self.yesterday,
                },
            ),
            # obey Expires if max-age is not present
            (
                200,
                {
                    "Date": self.yesterday,
                    "Age": "86400",
                    "Cache-Control": "public",
                    "Expires": self.tomorrow,
                    "Last-Modified": self.yesterday,
                },
            ),
            # Default missing Date header to right now
            (200, {"Expires": self.tomorrow}),
            # Firefox - Expires if age is greater than 10% of (Date - Last-Modified)
            (
                200,
                {
                    "Date": self.today,
                    "Last-Modified": self.yesterday,
                    "Age": str(86400 / 10 - 1),
                },
            ),
            # Firefox - Set one year maxage to permanent redirects missing expiration info
            (300, {}),
            (301, {}),
            (308, {}),
        ]
        with self._middleware() as mw:
            for idx, (status, headers) in enumerate(sampledata):
                req0 = Request(f"http://example-{idx}.com")
                res0 = Response(req0.url, status=status, headers=headers)
                # cache fresh response
                res1 = await self._process_requestresponse(mw, req0, res0)
                self.assertEqualResponse(res1, res0)
                assert "cached" not in res1.flags
                # return fresh cached response without network interaction
                res2 = await self._process_requestresponse(mw, req0, None)
                self.assertEqualResponse(res1, res2)
                assert "cached" in res2.flags
                # validate cached response if request max-age set as 0
                req1 = req0.replace(headers={"Cache-Control": "max-age=0"})
                res304 = res0.replace(status=304)
                assert await mw.process_request(req1) is None
                res3 = await self._process_requestresponse(mw, req1, res304)
                self.assertEqualResponse(res1, res3)
                assert "cached" in res3.flags

    @coroutine_test
    async def test_cached_and_stale(self):
        sampledata = [
            (200, {"Date": self.today, "Expires": self.yesterday}),
            (
                200,
                {
                    "Date": self.today,
                    "Expires": self.yesterday,
                    "Last-Modified": self.yesterday,
                },
            ),
            (200, {"Expires": self.yesterday}),
            (200, {"Expires": self.yesterday, "ETag": "foo"}),
            (200, {"Expires": self.yesterday, "Last-Modified": self.yesterday}),
            (200, {"Expires": self.tomorrow, "Age": "86405"}),
            (200, {"Cache-Control": "max-age=86400", "Age": "86405"}),
            # no-cache forces expiration, also revalidation if validators exists
            (200, {"Cache-Control": "no-cache"}),
            (200, {"Cache-Control": "no-cache", "ETag": "foo"}),
            (200, {"Cache-Control": "no-cache", "Last-Modified": self.yesterday}),
            (
                200,
                {
                    "Cache-Control": "no-cache,must-revalidate",
                    "Last-Modified": self.yesterday,
                },
            ),
            (
                200,
                {
                    "Cache-Control": "must-revalidate",
                    "Expires": self.yesterday,
                    "Last-Modified": self.yesterday,
                },
            ),
            (200, {"Cache-Control": "max-age=86400,must-revalidate", "Age": "86405"}),
        ]
        with self._middleware() as mw:
            for idx, (status, headers) in enumerate(sampledata):
                req0 = Request(f"http://example-{idx}.com")
                res0a = Response(req0.url, status=status, headers=headers)
                # cache expired response
                res1 = await self._process_requestresponse(mw, req0, res0a)
                self.assertEqualResponse(res1, res0a)
                assert "cached" not in res1.flags
                # Same request but as cached response is stale a new response must
                # be returned
                res0b = res0a.replace(body=b"bar")
                res2 = await self._process_requestresponse(mw, req0, res0b)
                self.assertEqualResponse(res2, res0b)
                assert "cached" not in res2.flags
                cc = headers.get("Cache-Control", "")
                # Previous response expired too, subsequent request to same
                # resource must revalidate and succeed on 304 if validators
                # are present
                if "ETag" in headers or "Last-Modified" in headers:
                    res0c = res0b.replace(status=304)
                    res3 = await self._process_requestresponse(mw, req0, res0c)
                    self.assertEqualResponse(res3, res0b)
                    assert "cached" in res3.flags
                    # get cached response on server errors unless must-revalidate
                    # in cached response
                    res0d = res0b.replace(status=500)
                    res4 = await self._process_requestresponse(mw, req0, res0d)
                    if "must-revalidate" in cc:
                        assert "cached" not in res4.flags
                        self.assertEqualResponse(res4, res0d)
                    else:
                        assert "cached" in res4.flags
                        self.assertEqualResponse(res4, res0b)
                # Requests with max-stale can fetch expired cached responses
                # unless cached response has must-revalidate
                req1 = req0.replace(headers={"Cache-Control": "max-stale"})
                res5 = await self._process_requestresponse(mw, req1, res0b)
                self.assertEqualResponse(res5, res0b)
                if "no-cache" in cc or "must-revalidate" in cc:
                    assert "cached" not in res5.flags
                else:
                    assert "cached" in res5.flags

    @coroutine_test
    async def test_middleware_ignore_schemes(self):
        # file responses are not cached by default
        req = Request("file:///tmp/t.txt")
        res = Response(req.url, headers={"Expires": self.tomorrow})
        with self._middleware() as mw:
            assert await mw.process_request(req) is None
            mw.process_response(req, res)

            assert mw.storage.retrieve_response(mw.crawler.spider, req) is None
            assert await mw.process_request(req) is None

    @coroutine_test
    async def test_max_stale_with_value(self):
        # A response that expired one day ago.
        headers = {"Date": self.yesterday, "Expires": self.yesterday}
        with self._middleware() as mw:
            req0 = Request("http://example.com")
            res0 = Response(req0.url, headers=headers)
            await self._process_requestresponse(mw, req0, res0)

            # max-stale greater than the staleness of the cached response
            req1 = req0.replace(headers={"Cache-Control": "max-stale=172800"})
            res1 = await mw.process_request(req1)
            assert isinstance(res1, Response)
            assert "cached" in res1.flags

            # max-stale lower than the staleness of the cached response
            req2 = req0.replace(headers={"Cache-Control": "max-stale=60"})
            assert await mw.process_request(req2) is None
            mw.process_exception(req2, IgnoreRequest())

            # a non-integer max-stale value is ignored
            req3 = req0.replace(headers={"Cache-Control": "max-stale=soon"})
            assert await mw.process_request(req3) is None

    @coroutine_test
    async def test_response_dated_in_the_future(self):
        # A Date header ahead of the local clock must not make the cached
        # response look aged.
        headers = {"Date": self.tomorrow, "Cache-Control": "max-age=10"}
        with self._middleware() as mw:
            req0 = Request("http://example.com")
            res0 = Response(req0.url, headers=headers)
            res1 = await self._process_requestresponse(mw, req0, res0)
            assert "cached" not in res1.flags

            res2 = await self._process_requestresponse(mw, req0, None)
            self.assertEqualResponse(res1, res2)
            assert "cached" in res2.flags

    @coroutine_test
    async def test_process_exception(self):
        with self._middleware() as mw:
            res0 = Response(self.request.url, headers={"Expires": self.yesterday})
            req0 = Request(self.request.url)
            await self._process_requestresponse(mw, req0, res0)
            for e in mw.DOWNLOAD_EXCEPTIONS:
                # Simulate encountering an error on download attempts
                assert await mw.process_request(req0) is None
                res1 = mw.process_exception(req0, e("foo"))
                # Use cached response as recovery
                assert isinstance(res1, Response)
                assert "cached" in res1.flags
                self.assertEqualResponse(res0, res1)
            # Do not use cached response for unhandled exceptions
            await mw.process_request(req0)
            assert mw.process_exception(req0, Exception("foo")) is None

    @coroutine_test
    async def test_ignore_response_cache_controls(self):
        sampledata = [
            (200, {"Date": self.yesterday, "Expires": self.tomorrow}),
            (200, {"Date": self.yesterday, "Cache-Control": "no-store,max-age=86405"}),
            (200, {"Age": "299", "Cache-Control": "max-age=300,no-cache"}),
            (300, {"Cache-Control": "no-cache"}),
            (200, {"Expires": self.tomorrow, "Cache-Control": "no-store"}),
        ]
        with self._middleware(
            HTTPCACHE_IGNORE_RESPONSE_CACHE_CONTROLS=["no-cache", "no-store"]
        ) as mw:
            for idx, (status, headers) in enumerate(sampledata):
                req0 = Request(f"http://example-{idx}.com")
                res0 = Response(req0.url, status=status, headers=headers)
                # cache fresh response
                res1 = await self._process_requestresponse(mw, req0, res0)
                self.assertEqualResponse(res1, res0)
                assert "cached" not in res1.flags
                # return fresh cached response without network interaction
                res2 = await self._process_requestresponse(mw, req0, None)
                self.assertEqualResponse(res1, res2)
                assert "cached" in res2.flags


# Concrete test classes that combine storage and policy mixins


class FilesystemStorageTestMixin(StorageTestMixin):
    storage_class = "scrapy.extensions.httpcache.FilesystemCacheStorage"

    def _corrupt_cache_entry(self, storage, spider, request) -> None:
        rpath = Path(storage._get_request_path(spider, request))
        (rpath / "response_body").unlink()


class DbmStorageTestMixin(StorageTestMixin):
    storage_class = "scrapy.extensions.httpcache.DbmCacheStorage"

    def _corrupt_cache_entry(self, storage, spider, request) -> None:
        key = storage._fingerprinter.fingerprint(request).hex()
        storage.db[f"{key}_data"] = b"not a pickle"


class TestFilesystemStorageWithDummyPolicy(
    FilesystemStorageTestMixin, DummyPolicyTestMixin
):
    policy_class = "scrapy.extensions.httpcache.DummyPolicy"


class TestFilesystemStorageWithRFC2616Policy(
    FilesystemStorageTestMixin, RFC2616PolicyTestMixin
):
    policy_class = "scrapy.extensions.httpcache.RFC2616Policy"


class TestDbmStorageWithDummyPolicy(DbmStorageTestMixin, DummyPolicyTestMixin):
    policy_class = "scrapy.extensions.httpcache.DummyPolicy"


class TestDbmStorageWithRFC2616Policy(DbmStorageTestMixin, RFC2616PolicyTestMixin):
    policy_class = "scrapy.extensions.httpcache.RFC2616Policy"


class TestDbmStorageWithCustomDbmModule(TestDbmStorageWithDummyPolicy):
    dbm_module = "tests.mocks.dummydbm"

    def _get_settings(self, **new_settings) -> dict[str, Any]:
        new_settings.setdefault("HTTPCACHE_DBM_MODULE", self.dbm_module)
        return super()._get_settings(**new_settings)

    def test_custom_dbm_module_loaded(self):
        # make sure our dbm module has been loaded
        with self._storage() as (storage, _):
            assert storage.dbmodule.__name__ == self.dbm_module


class TestFilesystemStorageGzipWithDummyPolicy(TestFilesystemStorageWithDummyPolicy):
    def _get_settings(self, **new_settings) -> dict[str, Any]:
        new_settings.setdefault("HTTPCACHE_GZIP", True)
        return super()._get_settings(**new_settings)

    def _corrupt_cache_entry(self, storage, spider, request) -> None:
        # A spider killed while writing a gzip file leaves it truncated.
        body_path = Path(storage._get_request_path(spider, request), "response_body")
        body_path.write_bytes(body_path.read_bytes()[:-5])


class _LateMiddleware:
    """Downloader middleware that runs after :class:`HttpCacheMiddleware`."""

    priority = 950


class _IgnoreOnRequest(_LateMiddleware):
    def __init__(self) -> None:
        self.gate: Deferred[None] = Deferred()

    async def process_request(self, request: Request) -> None:
        await maybe_deferred_to_future(self.gate)
        raise IgnoreRequest


class _RaiseOnResponse(_LateMiddleware):
    def process_response(self, request: Request, response: Response) -> Response:
        raise ValueError("Late middleware failure")


class _RedirectOnResponse(_LateMiddleware):
    def process_response(self, request: Request, response: Response) -> Request:
        return Request("http://www.example.com/elsewhere")


class _Downloads:
    """Download function that records its calls and, until released, blocks."""

    def __init__(self, status: int = 200) -> None:
        self.urls: list[str] = []
        self.status = status
        self.blocking = True
        self._blocked: list[Deferred[None]] = []

    async def __call__(self, request: Request) -> Response:
        self.urls.append(request.url)
        if self.blocking:
            blocked: Deferred[None] = Deferred()
            self._blocked.append(blocked)
            await maybe_deferred_to_future(blocked)
        return Response(request.url, status=self.status, body=b"body")

    def release(self) -> None:
        self.blocking = False
        while self._blocked:
            self._blocked.pop(0).callback(None)


class TestConcurrentDownloads(TestBase):
    """Requests for a resource that a concurrent request is already
    downloading wait for that download and read its response from the
    cache."""

    policy_class = "scrapy.extensions.httpcache.DummyPolicy"
    storage_class = "scrapy.extensions.httpcache.FilesystemCacheStorage"
    url = "http://www.example.com"

    @contextmanager
    def _manager(
        self, *late_middlewares: type[_LateMiddleware], **new_settings: Any
    ) -> Generator[tuple[DownloaderMiddlewareManager, Crawler]]:
        new_settings.setdefault(
            "DOWNLOADER_MIDDLEWARES",
            {mw: mw.priority for mw in late_middlewares},
        )
        with self._get_crawler(**new_settings) as crawler:
            manager = DownloaderMiddlewareManager.from_crawler(crawler)
            crawler.signals.send_catch_log(signals.spider_opened, spider=crawler.spider)
            try:
                yield manager, crawler
            finally:
                crawler.signals.send_catch_log(
                    signals.spider_closed, spider=crawler.spider, reason="finished"
                )

    @staticmethod
    def _middleware_of(manager: DownloaderMiddlewareManager, base: type) -> Any:
        return next(mw for mw in manager.middlewares if isinstance(mw, base))

    @staticmethod
    async def _wait_until(condition: Callable[[], Any]) -> None:
        for _ in range(100):
            if condition():
                return
            await _defer_sleep_async()
        raise AssertionError("The expected state was never reached")

    async def _start(
        self,
        manager: DownloaderMiddlewareManager,
        download: _Downloads,
        crawler: Crawler,
    ) -> tuple[Request, Deferred[Any], Deferred[Any]]:
        """Start two concurrent requests for the same URL, the second one
        waiting for the first one.

        Return the first request, which callers must keep a reference to for
        as long as they do not want it garbage-collected, and the results of
        both requests.
        """
        request = Request(self.url)
        first = deferred_from_coro(manager.download_async(download, request))
        await self._wait_until(lambda: download.urls)
        second = deferred_from_coro(manager.download_async(download, Request(self.url)))
        stats = crawler.stats
        assert stats
        await self._wait_until(lambda: stats.get_value("httpcache/wait"))
        return request, first, second

    @coroutine_test
    async def test_cached(self):
        with self._manager() as (manager, crawler):
            download = _Downloads()
            _request, first, second = await self._start(manager, download, crawler)
            download.release()

            assert isinstance(await maybe_deferred_to_future(first), Response)
            response = await maybe_deferred_to_future(second)
            assert isinstance(response, Response)
            assert "cached" in response.flags
            assert response.body == b"body"
            assert download.urls == [self.url]

    @coroutine_test
    async def test_uncacheable_response(self):
        with self._manager(HTTPCACHE_IGNORE_HTTP_CODES=[404]) as (manager, crawler):
            download = _Downloads(status=404)
            _request, first, second = await self._start(manager, download, crawler)
            download.release()

            for result in (first, second):
                response = await maybe_deferred_to_future(result)
                assert isinstance(response, Response)
                assert "cached" not in response.flags
            assert download.urls == [self.url] * 2

    @coroutine_test
    async def test_download_exception(self):
        with self._manager() as (manager, crawler):
            download = _Downloads()
            _request, first, second = await self._start(manager, download, crawler)
            download._blocked.pop(0).errback(ValueError("Download failure"))

            with pytest.raises(ValueError, match="Download failure"):
                await maybe_deferred_to_future(first)
            download.release()
            assert isinstance(await maybe_deferred_to_future(second), Response)
            assert download.urls == [self.url] * 2

    @coroutine_test
    async def test_ignored_by_a_later_middleware(self):
        with self._manager(_IgnoreOnRequest) as (manager, crawler):
            download = _Downloads()
            late = self._middleware_of(manager, _IgnoreOnRequest)
            middleware = self._middleware_of(manager, HttpCacheMiddleware)
            request = Request(self.url)
            first = deferred_from_coro(manager.download_async(download, request))
            await self._wait_until(lambda: middleware._downloading)
            second = deferred_from_coro(
                manager.download_async(download, Request(self.url))
            )
            stats = crawler.stats
            assert stats
            await self._wait_until(lambda: stats.get_value("httpcache/wait"))
            late.gate.callback(None)

            for result in (first, second):
                with pytest.raises(IgnoreRequest):
                    await maybe_deferred_to_future(result)
            assert not download.urls

    @coroutine_test
    async def test_response_replaced_by_a_later_middleware(self):
        # A middleware with a higher priority returning a request from
        # process_response() keeps HttpCacheMiddleware.process_response() from
        # running, so waiters are only woken up once the first request object
        # is garbage-collected.
        with self._manager(_RedirectOnResponse) as (manager, crawler):
            download = _Downloads()
            request, first, second = await self._start(manager, download, crawler)
            middleware = self._middleware_of(manager, HttpCacheMiddleware)
            download.release()

            assert isinstance(await maybe_deferred_to_future(first), Request)
            assert middleware._downloading

            def collected() -> bool:
                gc.collect()
                return not middleware._downloading

            del request
            await self._wait_until(collected)
            assert isinstance(await maybe_deferred_to_future(second), Request)
            assert download.urls == [self.url] * 2

    @coroutine_test
    async def test_response_error_in_a_later_middleware(self):
        # A middleware with a higher priority raising from process_response()
        # also keeps HttpCacheMiddleware.process_response() from running, but
        # here the resulting failure keeps the first request object alive, so
        # waiters block until the spider is closed.
        with self._manager(_RaiseOnResponse) as (manager, crawler):
            download = _Downloads()
            request, first, second = await self._start(manager, download, crawler)
            middleware = self._middleware_of(manager, HttpCacheMiddleware)
            download.release()

            with pytest.raises(ValueError, match="Late middleware failure"):
                await maybe_deferred_to_future(first)
            del request
            gc.collect()
            assert middleware._downloading
            assert not second.called

            middleware.spider_closed(crawler.spider)
            with pytest.raises(ValueError, match="Late middleware failure"):
                await maybe_deferred_to_future(second)
            assert download.urls == [self.url] * 2

    @coroutine_test
    async def test_cancelled_waiter(self):
        with self._manager() as (manager, crawler):
            download = _Downloads()
            _request, first, second = await self._start(manager, download, crawler)
            second.cancel()
            download.release()

            assert isinstance(await maybe_deferred_to_future(first), Response)
            assert download.urls == [self.url]
            assert not self._middleware_of(manager, HttpCacheMiddleware)._downloading


class TestInFlightTracking(TestBase):
    """Bookkeeping of requests that are being downloaded."""

    policy_class = "scrapy.extensions.httpcache.DummyPolicy"
    storage_class = "scrapy.extensions.httpcache.FilesystemCacheStorage"
    url = "http://www.example.com"

    @coroutine_test
    async def test_garbage_collected_request(self):
        with self._middleware() as mw:
            request = Request(self.url)
            assert await mw.process_request(request) is None
            assert mw._downloading

            del request
            gc.collect()
            assert not mw._downloading

    @coroutine_test
    async def test_same_request_twice(self):
        with self._middleware() as mw:
            request = Request(self.url)
            assert await mw.process_request(request) is None
            assert await mw.process_request(request) is None

    @coroutine_test
    async def test_spider_closed(self):
        with self._middleware() as mw:
            request = Request(self.url)
            assert await mw.process_request(request) is None
            waiting = deferred_from_coro(mw.process_request(Request(self.url)))
            assert mw.crawler.stats
            for _ in range(100):
                if mw.crawler.stats.get_value("httpcache/wait"):
                    break
                await _defer_sleep_async()
            assert not waiting.called

            fingerprint = mw._fingerprinter.fingerprint(request)
            waiters = mw._downloading[fingerprint]

            assert mw.crawler.spider
            mw.spider_closed(mw.crawler.spider)
            assert await maybe_deferred_to_future(waiting) is None
            # The woken request found no cache entry, so it took over as the
            # in-flight download, with a fresh list of waiters.
            assert not waiters
            assert mw._downloading.get(fingerprint) is not waiters