mypy: Upgrade to PyQt5-stubs 5.15.6.0

For some unknown reason, those new stubs cause a *lot* of things now to be
checked by mypy which formerly probably got skipped due to Any being implied
somewhere.

The stubs themselves mainly improved, with a couple of regressions too.

In total, there were some 337 (!) new mypy errors. This commit fixes almost all
of them, and the next commit improves a fix to get things down to 0 errors
again.

Overview of the changes:

==== qutebrowser/app.py

- Drop type ignore due to improved stubs.

==== qutebrowser/browser/browsertab.py

- Specify the type of _widget members more closely than just QWidget.
  This is debatable: I suppose the abstract stuff shouldn't need to know
  anything about the concrete backends at all. But it seems like we cut some
  corners when initially implementing things, and put some code in browsertab.py
  just because the APIs of both backends happened to be compatible. Perhaps
  something to reconsider once we drop QtWebKit and hopefully implement a dummy
  backend.

- Add an additional assertion in AbstractAction.run_string. This is already
  covered by the isinstance(member, self.action_base) above it, but that's too
  dynamic for mypy to understand.

- Fix the return type of AbstractScroller.pos_px, which is a QPoint (with x
  and y components), not a single int.

- Fix the return type of AbstractScroller.pos_perc, which is a Tuple (with x
  and y components), not a single int.

- Fix the argument types of AbstractScroller.to_perc, as it's possible to pass
  fractional percentages too.

- Specify the type for AbstractHistoryPrivate._history. See above (_widget) re
  this being debatable.

- Fix the return type of AbstractTabPrivate.event_target(), which can be None
  (see #3888).

- Fix the return type of AbstractTabPrivate.run_js_sync, which is Any (the JS
  return value), not None.

- Fix the argument type for AbstractTabPrivate.toggle_inspector: position can
  be None to use the last used position.

- Declare the type of sub-objects of AbstractTab.

- Fix the return value of AbstractTab.icon(), which is the QIcon, not None.

==== qutebrowser/browser/commands.py

- Make sure the active window is a MainWindow (with a .win_id attribute).

==== qutebrowser/browser/downloadview.py

- Add _model() which makes sure that self.model() is a DownloadModel, not None
  or any other model. This is needed because other methods access a variety of
  custom attributes on it, e.g. last_index().

==== qutebrowser/browser/greasemonkey.py

- Add an ignore for AbstractDownload.requested_url which we patch onto the
  downloads. Probably would be nicer to add it as a proper attribute which always
  gets set by the DownloadManager.

==== qutebrowser/browser/hints.py

- Remove type ignores for QUrl.toString().
- Add a new type ignore for combining different URL flags (which works, but is
  not exactly type safe... still probably a regression in the stubs).
- Make sure the things we get back from self._get_keyparser are what we actually
  expect. Probably should introduce a TypedDict (and/or overloads for
  _get_keyparser with typing.Literal) to teach mypy about the exact return value.
  See #7098.
  This is needed because we access Hint/NormalKeyParser-specific attributes such
  as .set_inhibited_timout() or .update_bindings().

==== qutebrowser/browser/inspector.py

- Similar changes than in browsertab.py to make some types where we share API
  (e.g. .setPage()) more concrete. Didn't work out unfortunately, see next
  commit.

==== qutebrowser/browser/network/pac.py

- Remove now unneeded type ignore for signal.

==== qutebrowser/browser/qtnetworkdownloads.py

- Make sure that downloads is a qtnetworkdownloads.DownloadItem (rather than an
  AbstractDownload), so that we can call ._uses_nam() on it.

==== qutebrowser/browser/qutescheme.py

- Remove now unneeded type ignore for QUrl flags.

==== qutebrowser/browser/urlmarks.py

- Specify the type of UrlMarkManager._lineparser, as those only get initialized
  in _init_lineparser of subclasses, so mypy doesn't know it's supposed to exist.

==== qutebrowser/browser/webelem.py

- New casts to turn single KeyboardModifier (enum) entries into
  KeyboardModifiers (flags). Might not be needed anymore with Qt 6.
- With that, casting the final value is now unneeded.

==== qutebrowser/browser/webengine/notification.py

- Remove now unneeded type ignore for signal.
- Make sure the self.sender() we get in HerbeNotificationAdapter._on_finished()
  is a QProcess, not just any QObject.

==== qutebrowser/browser/webengine/webenginedownloads.py

- Remove now unneeded type ignores for signals.

==== qutebrowser/browser/webengine/webengineelem.py

- Specify the type of WebEngineElement._tab.
- Remove now unneeded type ignore for mixed flags.

==== qutebrowser/browser/webengine/webengineinspector.py

- See changes to inspector.py and next commit.
- Remove now unneeded type ignore for signal.

==== qutebrowser/browser/webengine/webenginequtescheme.py

- Remove now unneeded type ignore for mixed flags.

==== qutebrowser/browser/webengine/webenginesettings.py

- Ignore access of .setter attribute which we patch onto QWebEngineProfile.
  Would be nice to have a subclass or wrapper-class instead.

==== qutebrowser/browser/webengine/webenginetab.py

- Specified the type of _widget members more closely than just QWidget.
  See browsertab.py changes for details.
- Remove some now-unneeded type ignores for creating FindFlags.
- Specify more concrete types for WebEngineTab members where we actually need to
  access WebEngine-specific attributes.
- Make sure the page we get is our custom WebEnginePage subclass, not just any
  QWebEnginePage. This is needed because we access custom attributes on it.

==== qutebrowser/browser/webengine/webview.py

- Make sure the page we get is our custom WebEnginePage subclass, not just any
  QWebEnginePage. This is needed because we access custom attributes on it.

==== qutebrowser/browser/webkit/network/networkreply.py

- Remove now unneeded type ignores for signals.

==== qutebrowser/browser/webkit/webkitinspector.py

- See changes to inspector.py and next commit.

==== qutebrowser/browser/webkit/webkittab.py

- Specify the type of _widget members more closely than just QWidget.
  See browsertab.py changes for details.
- Add a type ignore for WebKitAction because our workaround needs to
  treat them as ints (which is allowed by PyQt, even if not type-safe).
- Add new ignores for findText calls: The text is a QString and can be None; the
  flags are valid despite mypy thinking they aren't (stubs regression?).
- Specify the type for WebKitHistoryPrivate._history, because we access
  WebKit-specific attributes. See above (_widget) re this being debatable.
- Make mypy aware that .currentFrame() and .frameAt() can return None (stubs
  regression?).
- Make sure the .page() and .page().networkAccessManager() are our subclasses
  rather than the more generic QtWebKit objects, as we use custom attributes.
- Add new type ignores for signals (stubs regression!)

==== qutebrowser/browser/webkit/webpage.py

- Make sure the .networkAccessManager() is our subclass rather than the more
  generic QtWebKit object, as we use custom attributes.
- Replace a cast by a type ignore. The cast didn't work anymore.

==== qutebrowser/browser/webkit/webview.py

- Make sure the .page() is our subclass rather than the more generic QtWebKit
  object, as we use custom attributes.

==== qutebrowser/commands/userscripts.py

- Remove now unneeded type ignore for signal.

==== qutebrowser/completion/completer.py

- Add a new _completion() getter (which ensures it actually gets the completion
  view) rather than accessing the .parent() directly (which could be any QObject).

==== qutebrowser/completion/completiondelegate.py

- Make sure self.parent() is a CompletionView (no helper method as there is only
  one instance).
- Remove a now-unneeded type ignore for adding QSizes.

==== qutebrowser/completion/completionwidget.py

- Add a ._model() getter which ensures that we get a CompletionModel (with
  custom attributes) rather than Qt's .model() which can be any QAbstractItemModel
  (or None).
- Removed a now-unneeded type ignore for OR-ing flags.

==== qutebrowser/completion/models/completionmodel.py

- Remove now unneeded type ignores for signals.
- Ignore a complaint about .set_pattern() not being defined. Completion
  categories don't share any common parent class, so it would be good to introduce
  a typing.Protocol for this. See #7098.

==== qutebrowser/components/misccommands.py

- Removed a now-unneeded type ignore for OR-ing flags.

==== qutebrowser/components/readlinecommands.py

- Make sure QApplication.instance() is a QApplication (and not just a
  QCoreApplication). This includes the former "not None" check.

==== qutebrowser/components/scrollcommands.py

- Add basic annotation for "funcs" dict. Could have a callable protocol to
  specify it needs a count kwarg, see #7098.

==== qutebrowser/config/stylesheet.py

- Correctly specify that stylesheet apply to QWidgets, not any QObject.
- Ignore an attr-defined for obj.STYLESHEET. Perhaps could somehow teach mypy
  about this with overloads and protocols (stylesheet for set_register being None
  => STYLESHEET needs to be defined, otherwise anything goes), but perhaps not
  worth the troble. See #7098.

==== qutebrowser/keyinput/keyutils.py

- Remove some now-unneeded type ignores and add a cast for using a single enum
  value as flags. Might need to look at this again with Qt 6 support.

==== qutebrowser/keyinput/modeman.py

- Add a FIXME for using a TypedDict, see comments for hints.py above.

==== qutebrowser/mainwindow/mainwindow.py

- Remove now-unneeded type ignores for calling with OR-ed flags.
- Improve where we cast from WindowType to WindowFlags, no int needed
- Use new .tab_bar() getter, see below.

==== qutebrowser/mainwindow/prompt.py

- Remove now-unneeded type ignores for calling with OR-ed flags.

==== qutebrowser/mainwindow/statusbar/bar.py

- Adjust type ignores around @pyqtProperty. The fact one is still needed seems
  like a stub regression.

==== qutebrowser/mainwindow/statusbar/command.py

- Fix type for setText() override (from QLineEdit): text can be None
  (QString in C++).

==== qutebrowser/mainwindow/statusbar/url.py

- Adjust type ignores around @pyqtProperty. The fact one is still needed seems
  like a stub regression.

==== qutebrowser/mainwindow/tabbedbrowser.py

- Specify that TabDeque manages browser tabs, not any QWidgets. It accesses
  AbstractTab-specific attributes.
- Make sure that the .tabBar() we get is a tabwidget.TabBar, as we access
  .maybe_hide.
- Fix the annotations for stored marks: Scroll positions are a QPoint, not int.
- Add _current_tab() and _tab_by_idx() wrappers for .currentWidget() and
  .widget(), which ensures that the return values are valid AbstractTabs (or None
  for _tab_by_idx). This is needed because we access AbstractTab-specific
  attributes.
- For some places, where the tab can be None, continue using .currentTab() but
  add asserts.
- Remove some now-unneeded [unreachable] ignores, as mypy knows about the None
  possibility now.

==== qutebrowser/mainwindow/tabwidget.py

- Add new tab_bar() and _tab_by_idx() helpers which check that the .tabBar() and
  .widget() are of type TabBar and AbstractTab, respectively.
- Add additional assertions where we expect ._tab_by_idx() to never be None.
- Remove dead code in get_tab_fields for handling a None y scroll position. I
  was unable to find any place in the code where this could be set to None.
- Remove some now-unneeded type ignores and casts, as mypy now knows that
  _type_by_idx() could be None.
- Work around a strange instance where mypy complains about not being able to
  find the type of TabBar.drag_in_progress from TabWidget._toggle_visibility,
  despite it clearly being shown as a bool *inside* that class without any
  annotation.
- Add a ._tab_widget() getter in TabBar which ensures that the .parent() is in
  fact a TabWidget.

==== qutebrowser/misc/crashsignal.py

- Remove now unneeded type ignores for signals.

==== qutebrowser/misc/editor.py

- Remove now unneeded type ignores for signals.

==== qutebrowser/misc/ipc.py

- Remove now unneeded type ignores for signals.
- Add new type ignores for .error() which is both a signal and a getter
  (stub regression?). Won't be relevant for Qt 6 anymore, as the signal was
  renamed to errorOccurred in 5.15.

==== qutebrowser/misc/objects.py

- Make sure mypy knows that objects.app is our custom Application (with custom
  attributes) rather than any QApplication.

==== qutebrowser/utils/objreg.py

- Ignore attr-defined for .win_id attributes. Maybe could add a typing.Protocol,
  but ideally, the whole objreg stuff should die one day anyways.

==== tests/unit/completion/test_completer.py

- Make CompletionWidgetStub inherit from CompletionView so that it passes the
  new isinstance() asserts in completer.py (see above).

3 files changed, 5 insertions, 3 deletions

diff --git a/qutebrowser/components/misccommands.py b/qutebrowser/components/misccommands.py
index fe908b7d2..c20e8e290 100644
--- a/qutebrowser/components/misccommands.py
+++ b/qutebrowser/components/misccommands.py
@@ -83,7 +83,7 @@ def _print_preview(tab: apitypes.Tab) -> None:
     diag = QPrintPreviewDialog(tab)
     diag.setAttribute(Qt.WA_DeleteOnClose)
     diag.setWindowFlags(
-        diag.windowFlags() |  # type: ignore[operator, arg-type]
+        diag.windowFlags() |
         Qt.WindowMaximizeButtonHint |
         Qt.WindowMinimizeButtonHint)
     diag.paintRequested.connect(functools.partial(
diff --git a/qutebrowser/components/readlinecommands.py b/qutebrowser/components/readlinecommands.py
index 4ac03041c..37fa92127 100644
--- a/qutebrowser/components/readlinecommands.py
+++ b/qutebrowser/components/readlinecommands.py
@@ -42,7 +42,7 @@ class _ReadlineBridge:
         """Get the currently active QLineEdit."""
         # FIXME add this to api.utils or so
         qapp = QApplication.instance()
-        assert qapp is not None
+        assert isinstance(qapp, QApplication), qapp
         w = qapp.focusWidget()
 
         if isinstance(w, QLineEdit):
diff --git a/qutebrowser/components/scrollcommands.py b/qutebrowser/components/scrollcommands.py
index 757c23b2b..2287041d7 100644
--- a/qutebrowser/components/scrollcommands.py
+++ b/qutebrowser/components/scrollcommands.py
@@ -19,6 +19,7 @@
 
 """Scrolling-related commands."""
 
+from typing import Dict, Callable
 from qutebrowser.api import cmdutils, apitypes
 
 
@@ -54,7 +55,8 @@ def scroll(tab: apitypes.Tab, direction: str, count: int = 1) -> None:
                     (up/down/left/right/top/bottom).
         count: multiplier
     """
-    funcs = {
+    # FIXME:mypy Use a callback protocol to enforce having 'count'?
+    funcs: Dict[str, Callable[..., None]] = {
         'up': tab.scroller.up,
         'down': tab.scroller.down,
         'left': tab.scroller.left,