Greasemonkey: handle downloads that complete fast

When `@require`ing local files (with the `file://` scheme) the
greasemonkey manager was not catching the DownloadItem.finished signal
because it was being emitted before it had managed to connect.

I didn't see this happening while testing with files that should have
been in cache but I wouldn't be surprised.

I had to change the download mock to be able to give it the appearance
of asynchronicity. Now when using it one must set download.successful
appropriately before firing download.finished. I also added a list of
downloads to the stub so a test could enumerate them in case the
unit-under-test didn't have a reference to them.

qutebrowser/browser/greasemonkey.py

@@ -287,9 +287,12 @@ class GreasemonkeyManager(QObject):
                                             auto_remove=True)
             download.requested_url = url
             self._in_progress_dls.append(download)
-            download.finished.connect(
-                functools.partial(self._on_required_download_finished,
-                                  script, download))
+            if download.successful:
+                self._on_required_download_finished(script, download)
+            else:
+                download.finished.connect(
+                    functools.partial(self._on_required_download_finished,
+                                      script, download))
 
     def scripts_for(self, url):
         """Fetch scripts that are registered to run for url.

tests/helpers/fixtures.py

@@ -530,5 +530,5 @@ def download_stub(win_registry, tmpdir, stubs):
     """Register a FakeDownloadManager."""
     stub = stubs.FakeDownloadManager(tmpdir)
     objreg.register('qtnetwork-download-manager', stub)
-    yield
+    yield stub
     objreg.delete('qtnetwork-download-manager')

tests/helpers/stubs.py

@@ -572,7 +572,7 @@ class FakeDownloadItem(QObject):
         super().__init__(parent)
         self.fileobj = fileobj
         self.name = name
-        self.successful = True
+        self.successful = False
 
 
 class FakeDownloadManager:
@@ -581,6 +581,7 @@ class FakeDownloadManager:
 
     def __init__(self, tmpdir):
         self._tmpdir = tmpdir
+        self.downloads = []
 
     @contextlib.contextmanager
     def _open_fileobj(self, target):
@@ -603,4 +604,5 @@ class FakeDownloadManager:
             download_item = FakeDownloadItem(target.fileobj, name=url.path())
             with (self._tmpdir / url.path()).open('rb') as fake_url_file:
                 shutil.copyfileobj(fake_url_file, download_item.fileobj)
+        self.downloads.append(download_item)
         return download_item

tests/unit/browser/test_adblock.py

@@ -206,6 +206,7 @@ def test_disabled_blocking_update(basedir, config_stub, download_stub,
     while host_blocker._in_progress:
         current_download = host_blocker._in_progress[0]
         with caplog.at_level(logging.ERROR):
+            current_download.successful = True
             current_download.finished.emit()
     host_blocker.read_hosts()
     for str_url in URLS_TO_CHECK:
@@ -221,6 +222,8 @@ def test_no_blocklist_update(config_stub, download_stub,
     host_blocker = adblock.HostBlocker()
     host_blocker.adblock_update()
     host_blocker.read_hosts()
+    for dl in download_stub.downloads:
+        dl.successful = True
     for str_url in URLS_TO_CHECK:
         assert not host_blocker.is_blocked(QUrl(str_url))
 
@@ -238,6 +241,7 @@ def test_successful_update(config_stub, basedir, download_stub,
     while host_blocker._in_progress:
         current_download = host_blocker._in_progress[0]
         with caplog.at_level(logging.ERROR):
+            current_download.successful = True
             current_download.finished.emit()
     host_blocker.read_hosts()
     assert_urls(host_blocker, whitelisted=[])
@@ -265,6 +269,8 @@ def test_failed_dl_update(config_stub, basedir, download_stub,
         # if current download is the file we want to fail, make it fail
         if current_download.name == dl_fail_blocklist.path():
             current_download.successful = False
+        else:
+            current_download.successful = True
         with caplog.at_level(logging.ERROR):
             current_download.finished.emit()
     host_blocker.read_hosts()
@@ -294,16 +300,18 @@ def test_invalid_utf8(config_stub, download_stub, tmpdir, data_tmpdir,
 
     host_blocker = adblock.HostBlocker()
     host_blocker.adblock_update()
-    finished_signal = host_blocker._in_progress[0].finished
+    current_download = host_blocker._in_progress[0]
 
     if location == 'content':
         with caplog.at_level(logging.ERROR):
-            finished_signal.emit()
+            current_download.successful = True
+            current_download.finished.emit()
         expected = (r"Failed to decode: "
                     r"b'https://www.example.org/\xa0localhost")
         assert caplog.records[-2].message.startswith(expected)
     else:
-        finished_signal.emit()
+        current_download.successful = True
+        current_download.finished.emit()
 
     host_blocker.read_hosts()
     assert_urls(host_blocker, whitelisted=[])