Handle unknown filetypes with qute://help

doc/changelog.asciidoc

@@ -35,6 +35,7 @@ Fixed
 
 - More consistent sizing for favicons with vertical tabs.
 - Using `:home` on pinned tabs is now prevented.
+- Fix crash with unknown file types loaded via qute://help
 
 Deprecated
 ~~~~~~~~~~

qutebrowser/browser/qutescheme.py

@@ -29,8 +29,9 @@ import os
 import time
 import urllib.parse
 import textwrap
-import pkg_resources
+import mimetypes
 
+import pkg_resources
 from PyQt5.QtCore import QUrlQuery, QUrl
 
 import qutebrowser
@@ -323,8 +324,10 @@ def qute_help(url):
                       "scripts/asciidoc2html.py.")
 
     path = 'html/doc/{}'.format(urlpath)
-    if urlpath.endswith('.png'):
+    if not urlpath.endswith('.html'):
-        return 'image/png', utils.read_file(path, binary=True)
+        mimetype, _encoding = mimetypes.guess_type(urlpath)
+        assert mimetype is not None, url
+        return mimetype, utils.read_file(path, binary=True)
 
     try:
         data = utils.read_file(path)

tests/unit/browser/test_qutescheme.py

@@ -146,3 +146,26 @@ class TestHistoryHandler:
         url = QUrl("qute://history/data?start_time={}".format(now))
         _mimetype, data = benchmark(qutescheme.qute_history, url)
         assert len(json.loads(data)) > 1
+
+
+class TestHelpHandler:
+
+    """Tests for qute://help."""
+
+    @pytest.fixture
+    def data_patcher(self, monkeypatch):
+        def _patch(path, data):
+            def _read_file(name, binary=False):
+                assert path == name
+                if binary:
+                    return data
+                return data.decode('utf-8')
+
+            monkeypatch.setattr(qutescheme.utils, 'read_file', _read_file)
+        return _patch
+
+    def test_unknown_file_type(self, data_patcher):
+        data_patcher('html/doc/foo.bin', b'\xff')
+        mimetype, data = qutescheme.qute_help(QUrl('qute://help/foo.bin'))
+        assert mimetype == 'application/octet-stream'
+        assert data == b'\xff'