raise TypeError on invalid header assignment, fix #1562

netlib/http/headers.py

@@ -14,6 +14,7 @@ if six.PY2:  # pragma: no cover
         return x
 
     def _always_bytes(x):
+        strutils.always_bytes(x, "utf-8", "replace")  # raises a TypeError if x != str/bytes/None.
         return x
 else:
     # While headers _should_ be ASCII, it's not uncommon for certain headers to be utf-8 encoded.

netlib/strutils.py

@@ -8,7 +8,10 @@ import six
 def always_bytes(unicode_or_bytes, *encode_args):
     if isinstance(unicode_or_bytes, six.text_type):
         return unicode_or_bytes.encode(*encode_args)
+    elif isinstance(unicode_or_bytes, bytes) or unicode_or_bytes is None:
         return unicode_or_bytes
+    else:
+        raise TypeError("Expected str or bytes, but got {}.".format(type(unicode_or_bytes).__name__))
 
 
 def native(s, *encoding_opts):

test/netlib/http/test_headers.py

@@ -43,6 +43,15 @@ class TestHeaders(object):
         with raises(TypeError):
             Headers([[b"Host", u"not-bytes"]])
 
+    def test_set(self):
+        headers = Headers()
+        headers[u"foo"] = u"1"
+        headers[b"bar"] = b"2"
+        headers["baz"] = b"3"
+        with raises(TypeError):
+            headers["foobar"] = 42
+        assert len(headers) == 3
+
     def test_bytes(self):
         headers = Headers(Host="example.com")
         assert bytes(headers) == b"Host: example.com\r\n"

test/netlib/test_strutils.py

@@ -8,6 +8,8 @@ def test_always_bytes():
     assert strutils.always_bytes("foo") == b"foo"
     with tutils.raises(ValueError):
         strutils.always_bytes(u"\u2605", "ascii")
+    with tutils.raises(TypeError):
+        strutils.always_bytes(42, "ascii")
 
 
 def test_native():