treat E: and E:\ the same when downloading

Fixes #2305

qutebrowser/browser/downloads.py

@@ -583,6 +583,8 @@ class AbstractDownloadItem(QObject):
         """
         global last_used_directory
         filename = os.path.expanduser(filename)
+        if sys.platform == "win32":
+            filename = utils.expand_windows_drive(filename)
         self._ensure_can_set_filename(filename)
 
         self._filename = create_full_filename(self.basename, filename)

qutebrowser/browser/webkit/mhtml.py

@@ -554,6 +554,8 @@ def start_download_checked(target, tab):
     dest = utils.force_encoding(target.filename, encoding)
 
     dest = os.path.expanduser(dest)
+    if sys.platform == "win32":
+        dest = utils.expand_windows_drive(dest)
 
     # See if we already have an absolute path
     path = downloads.create_full_filename(default_name, dest)

qutebrowser/utils/utils.py

@@ -20,6 +20,7 @@
 """Other utilities which don't fit anywhere else."""
 
 import io
+import re
 import sys
 import enum
 import json
@@ -845,3 +846,21 @@ def open_file(filename, cmdline=None):
 def unused(_arg):
     """Function which does nothing to avoid pylint complaining."""
     pass
+
+
+def expand_windows_drive(path):
+    r"""Expand a drive-path like E: into E:\.
+
+    Does nothing for other paths.
+
+    Args:
+        path: The path to expand.
+    """
+    # Usually, "E:" on Windows refers to the current working directory on drive
+    # E:\. The correct way to specifify drive E: is "E:\", but most users
+    # probably don't use the "multiple working directories" feature and expect
+    # "E:" and "E:\" to be equal.
+    if re.match(r'[A-Z]:$', path, re.IGNORECASE):
+        return path + "\\"
+    else:
+        return path

tests/unit/utils/test_utils.py

@@ -916,3 +916,16 @@ class TestOpenFile:
 
 def test_unused():
     utils.unused(None)
+
+
+@pytest.mark.parametrize('path, expected', [
+    ('E:', 'E:\\'),
+    ('e:', 'e:\\'),
+    ('E:foo', 'E:foo'),
+    ('E:\\', 'E:\\'),
+    ('E:\\foo', 'E:\\foo'),
+    ('foo:', 'foo:'),
+    ('foo:bar', 'foo:bar'),
+])
+def test_expand_windows_drive(path, expected):
+    assert utils.expand_windows_drive(path) == expected