Accept 62- and 63-character simple hostname labels

src/validators/hostname.py

@@ -24,10 +24,10 @@ def _port_regex():
 @lru_cache
 def _simple_hostname_regex():
     """Simple hostname validation regex."""
-    # {0,59} because two characters are already matched at
-    # the beginning and at the end, making the range {1, 61}
+    # RFC 1035 limits each label to 63 octets. The first and last
+    # characters leave room for up to 61 characters in between.
     return re.compile(
-        r"^(?!-)[a-z0-9](?:[a-z0-9-]{0,59}[a-z0-9])?(?<!-)$", re.IGNORECASE | re.ASCII
+        r"^(?!-)[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?(?<!-)$", re.IGNORECASE | re.ASCII
     )
 
 

tests/test_hostname.py

@@ -171,3 +171,16 @@ def test_returns_true_on_valid_top_level_domain_hostname(value: str):
 def test_returns_failed_validation_on_invalid_top_level_domain_hostname(value: str):
     """Test returns failed validation on hostname with a TLD not allowed by IANA."""
     assert isinstance(hostname(value, consider_tld=True), ValidationError)
+
+
+@pytest.mark.parametrize("length", [1, 61, 62, 63, 64])
+@pytest.mark.parametrize("port", ["", ":8080"])
+@pytest.mark.parametrize("rfc_1034", [False, True])
+def test_simple_hostname_label_length(length: int, port: str, rfc_1034: bool):
+    """Allow single labels up to 63 characters, with optional dots and ports."""
+    value = "a" * length + ("." if rfc_1034 else "") + port
+    result = hostname(value, rfc_1034=rfc_1034)
+    if length <= 63:
+        assert result is True
+    else:
+        assert isinstance(result, ValidationError)

tests/test_url.py

@@ -299,3 +299,14 @@ def test_returns_true_on_valid_top_level_domain_url(value: str):
 def test_returns_failed_validation_on_invalid_top_level_domain_url(value: str):
     """Test returns failed validation on url with a TLD not allowed by IANA."""
     assert isinstance(url(value, consider_tld=True), ValidationError)
+
+
+@pytest.mark.parametrize("length", [61, 62, 63, 64])
+@pytest.mark.parametrize("port", ["", ":8080"])
+def test_url_simple_hostname_label_length(length: int, port: str):
+    """Apply the 63-character label limit to URLs allowing simple hosts."""
+    result = url("http://" + "a" * length + port + "/", simple_host=True)
+    if length <= 63:
+        assert result is True
+    else:
+        assert isinstance(result, ValidationError)