Honour --no-err-windows in more places

Fixes #3053

qutebrowser/misc/backendproblem.py

@@ -52,22 +52,20 @@ class _Button:
     default = attr.ib(default=False)
 
 
-class _Dialog(QDialog):
+def _other_backend(backend):
+    """Get the other backend enum/setting for a given backend."""
+    other_backend = {
+        usertypes.Backend.QtWebKit: usertypes.Backend.QtWebEngine,
+        usertypes.Backend.QtWebEngine: usertypes.Backend.QtWebKit,
+    }[backend]
+    other_setting = other_backend.name.lower()[2:]
+    return (other_backend, other_setting)
 
-    """A dialog which gets shown if there are issues with the backend."""
 
-    def __init__(self, because, text, backend, buttons=None, parent=None):
-        super().__init__(parent)
-        vbox = QVBoxLayout(self)
-
-        other_backend = {
-            usertypes.Backend.QtWebKit: usertypes.Backend.QtWebEngine,
-            usertypes.Backend.QtWebEngine: usertypes.Backend.QtWebKit,
-        }[backend]
-        other_setting = other_backend.name.lower()[2:]
-
-        label = QLabel(
-            "<b>Failed to start with the {backend} backend!</b>"
+def _error_text(because, text, backend):
+    """Get an error text for the given information."""
+    other_backend, other_setting = _other_backend(backend)
+    return ("<b>Failed to start with the {backend} backend!</b>"
             "<p>qutebrowser tried to start with the {backend} backend but "
             "failed because {because}.</p>{text}"
             "<p><b>Forcing the {other_backend.name} backend</b></p>"
@@ -76,8 +74,21 @@ class _Dialog(QDialog):
             "(if you have a <i>config.py</i> file, you'll need to set "
             "this manually).</p>".format(
                 backend=backend.name, because=because, text=text,
-                other_backend=other_backend, other_setting=other_setting),
-            wordWrap=True)
+                other_backend=other_backend, other_setting=other_setting))
+
+
+class _Dialog(QDialog):
+
+    """A dialog which gets shown if there are issues with the backend."""
+
+    def __init__(self, because, text, backend, buttons=None, parent=None):
+        super().__init__(parent)
+        vbox = QVBoxLayout(self)
+
+        other_backend, other_setting = _other_backend(backend)
+        text = _error_text(because, text, backend)
+
+        label = QLabel(text, wordWrap=True)
         label.setTextFormat(Qt.RichText)
         vbox.addWidget(label)
 
@@ -118,6 +129,12 @@ class _Dialog(QDialog):
 
 def _show_dialog(*args, **kwargs):
     """Show a dialog for a backend problem."""
+    cmd_args = objreg.get('args')
+    if cmd_args.no_err_windows:
+        text = _error_text(*args, **kwargs)
+        print(text, file=sys.stderr)
+        sys.exit(usertypes.Exit.err_init)
+
     dialog = _Dialog(*args, **kwargs)
 
     status = dialog.exec_()

qutebrowser/misc/msgbox.py

@@ -19,10 +19,21 @@
 
 """Convenience functions to show message boxes."""
 
+import sys
 
 from PyQt5.QtCore import Qt
 from PyQt5.QtWidgets import QMessageBox
 
+from qutebrowser.utils import objreg
+
+
+class DummyBox:
+
+    """A dummy QMessageBox returned when --no-err-windows is used."""
+
+    def exec_(self):
+        pass
+
 
 def msgbox(parent, title, text, *, icon, buttons=QMessageBox.Ok,
            on_finished=None, plain_text=None):
@@ -40,6 +51,11 @@ def msgbox(parent, title, text, *, icon, buttons=QMessageBox.Ok,
     Return:
         A new QMessageBox.
     """
+    args = objreg.get('args')
+    if args.no_err_windows:
+        print('Message box: {}; {}'.format(title, text), file=sys.stderr)
+        return DummyBox()
+
     box = QMessageBox(parent)
     box.setAttribute(Qt.WA_DeleteOnClose)
     box.setIcon(icon)

tests/unit/misc/test_msgbox.py

@@ -27,6 +27,11 @@ from PyQt5.QtCore import Qt
 from PyQt5.QtWidgets import QMessageBox, QWidget
 
 
+@pytest.fixture(autouse=True)
+def patch_args(fake_args):
+    fake_args.no_err_windows = False
+
+
 def test_attributes(qtbot):
     """Test basic QMessageBox attributes."""
     title = 'title'
@@ -85,3 +90,12 @@ def test_information(qtbot):
         assert box.windowTitle() == 'foo'
     assert box.text() == 'bar'
     assert box.icon() == QMessageBox.Information
+
+
+def test_no_err_windows(fake_args, capsys):
+    fake_args.no_err_windows = True
+    box = msgbox.information(parent=None, title='foo', text='bar')
+    box.exec_()  # should do nothing
+    out, err = capsys.readouterr()
+    assert not out
+    assert err == 'Message box: foo; bar\n'