Adjust filename suffix matching for Qt 5.12

https://codereview.qt-project.org/#/c/247517/
https://chromium-review.googlesource.com/c/chromium/src/+/1278137
https://cs.chromium.org/chromium/src/base/time/time_to_iso8601.cc

Fixes #4478
Fixes #4580

qutebrowser/browser/webengine/webenginedownloads.py

@@ -180,7 +180,21 @@ def _get_suggested_filename(path):
     See https://bugreports.qt.io/browse/QTBUG-56978
     """
     filename = os.path.basename(path)
-    filename = re.sub(r'\([0-9]+\)(?=\.|$)', '', filename)
+
+    suffix_re = re.compile(r"""
+      \ ?  # Optional space between filename and suffix
+      (
+        # Numerical suffix
+        \([0-9]+\)
+      |
+        # ISO-8601 suffix
+        # https://cs.chromium.org/chromium/src/base/time/time_to_iso8601.cc
+        \ -\ \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}.\d{3}Z
+      )
+      (?=\.|$)  # Begin of extension, or filename without extension
+    """, re.VERBOSE)
+
+    filename = suffix_re.sub('', filename)
     if not qtutils.version_check('5.9', compiled=False):
         # https://bugreports.qt.io/browse/QTBUG-58155
         filename = urllib.parse.unquote(filename)

tests/unit/browser/webengine/test_webenginedownloads.py

@@ -30,6 +30,8 @@ from helpers import utils
 @pytest.mark.parametrize('path, expected', [
     (os.path.join('subfolder', 'foo'), 'foo'),
     ('foo(1)', 'foo'),
+    ('foo (1)', 'foo'),
+    ('foo - 1970-01-01T00:00:00.000Z', 'foo'),
     ('foo(a)', 'foo(a)'),
     ('foo1', 'foo1'),
     pytest.param('foo%20bar', 'foo bar', marks=utils.qt58),