fix: validate port range and reject empty hosts in _parse_address

Ports outside TCP range 1-65535 (including 0, negative, >65535) were
silently accepted, producing confusing OS-level errors downstream.
Empty hostnames (":9001") were also accepted. Additionally, unbracketed
IPv6 addresses like "fe80::1:9001" were ambiguously misparsed.

Add port range validation, empty hostname rejection, and a heuristic
that detects unbracketed IPv6 (host contains multiple colons) and
directs users to use bracket notation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqliteclient/connection.py

@@ -43,6 +43,15 @@ def _parse_address(address: str) -> tuple[str, int]:
             f"Invalid port in address {address!r}: {port_str!r} is not a number"
         ) from None
 
+    if not (1 <= port <= 65535):
+        raise ValueError(f"Invalid port in address {address!r}: {port} is not in range 1-65535")
+    if not host:
+        raise ValueError(f"Invalid address format: empty hostname in {address!r}")
+    if host.count(":") > 1 and not address.startswith("["):
+        raise ValueError(
+            f"IPv6 addresses must be bracketed: use '[{host}]:{port}' instead of {address!r}"
+        )
+
     return host, port
 
 

tests/test_connection.py

@@ -47,6 +47,46 @@ def test_ipv6_no_port_raises(self) -> None:
         with pytest.raises(ValueError, match="expected.*host.*port"):
             _parse_address("[::1]")
 
+    def test_port_zero_raises(self) -> None:
+        from dqliteclient.connection import _parse_address
+
+        with pytest.raises(ValueError, match="not in range"):
+            _parse_address("host:0")
+
+    def test_port_negative_raises(self) -> None:
+        from dqliteclient.connection import _parse_address
+
+        with pytest.raises(ValueError, match="not in range"):
+            _parse_address("host:-1")
+
+    def test_port_too_large_raises(self) -> None:
+        from dqliteclient.connection import _parse_address
+
+        with pytest.raises(ValueError, match="not in range"):
+            _parse_address("host:65536")
+
+    def test_empty_host_raises(self) -> None:
+        from dqliteclient.connection import _parse_address
+
+        with pytest.raises(ValueError, match="empty hostname"):
+            _parse_address(":9001")
+
+    def test_unbracketed_ipv6_raises(self) -> None:
+        from dqliteclient.connection import _parse_address
+
+        with pytest.raises(ValueError, match="must be bracketed"):
+            _parse_address("fe80::1:9001")
+
+    def test_max_valid_port(self) -> None:
+        from dqliteclient.connection import _parse_address
+
+        assert _parse_address("host:65535") == ("host", 65535)
+
+    def test_min_valid_port(self) -> None:
+        from dqliteclient.connection import _parse_address
+
+        assert _parse_address("host:1") == ("host", 1)
+
 
 class TestDqliteConnection:
     def test_zero_timeout_raises(self) -> None: