Accept trailing dot on simple hostnames with rfc_1034

hostname('ie', rfc_1034=True) is valid, but hostname('ie.', rfc_1034=True)
was rejected. The RFC 1034 trailing dot was only handled by domain() (for
dotted names); a simple, single-label hostname went through
_simple_hostname_regex(), which does not allow a trailing dot, so it failed.

Strip an optional trailing dot before the simple-hostname check when
rfc_1034 is set, so a single-label hostname behaves consistently with and
without the dot. The dot is still rejected when rfc_1034 is False.

Refs #442

Author: assinscreedFC

src/validators/hostname.py

@@ -113,16 +113,25 @@ def hostname(
     if not value:
         return False
 
+    def _matches_simple_hostname(host: str):
+        if not maybe_simple:
+            return False
+        # A trailing dot (RFC 1034) is also valid on a simple, single-label
+        # hostname, not only on the dotted names handled by `domain()`.
+        if rfc_1034 and host.endswith("."):
+            host = host[:-1]
+        return _simple_hostname_regex().match(host)
+
     if may_have_port and (host_seg := _port_validator(value)):
         return (
-            (_simple_hostname_regex().match(host_seg) if maybe_simple else False)
+            _matches_simple_hostname(host_seg)
             or domain(host_seg, consider_tld=consider_tld, rfc_1034=rfc_1034, rfc_2782=rfc_2782)
             or (False if skip_ipv4_addr else ipv4(host_seg, cidr=False, private=private))
             or (False if skip_ipv6_addr else ipv6(host_seg, cidr=False))
         )
 
     return (
-        (_simple_hostname_regex().match(value) if maybe_simple else False)
+        _matches_simple_hostname(value)
         or domain(value, consider_tld=consider_tld, rfc_1034=rfc_1034, rfc_2782=rfc_2782)
         or (False if skip_ipv4_addr else ipv4(value, cidr=False, private=private))
         or (False if skip_ipv6_addr else ipv6(value, cidr=False))

tests/test_hostname.py

@@ -15,6 +15,9 @@
         ("this-pc", False, False),
         ("lab-01a-notebook:404", False, False),
         ("4-oh-4", False, False),
+        # simple, single-label hostname w/ trailing dot (RFC 1034); see #442
+        ("this-pc.", True, False),
+        ("ie.", True, False),
         # hostname w/ optional ports
         ("example.com:4444", False, False),
         ("kräuter.com.", True, False),
@@ -45,6 +48,8 @@ def test_returns_true_on_valid_hostname(value: str, rfc_1034: bool, rfc_2782: bo
         ("this-pc-is-sh*t", False, False),
         ("lab-01a-note._com_.com:404", False, False),
         ("4-oh-4:@.com", False, False),
+        # trailing dot is only allowed with rfc_1034; see #442
+        ("this-pc.", False, False),
         # bad (hostname w/ optional ports)
         ("example.com:-4444", False, False),
         ("xn----gtbspbbmkef.xn--p1ai:65538", False, False),