Validate schema parameter in params tuple encode/decode functions

encode_params_tuple and decode_params_tuple silently fell through to V0
encoding for any schema value other than 1 (e.g., 2, -1). Now raises
EncodeError/DecodeError for unsupported schema values.

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

Author: antoineleclair

src/dqlitewire/tuples.py

@@ -37,6 +37,9 @@ def encode_params_tuple(params: Sequence[Any], schema: int = 0, buffer_offset: i
             message body. Used to compute padding from the absolute position,
             matching Go's putNamedValues which pads based on m.Offset.
     """
+    if schema not in (0, 1):
+        raise EncodeError(f"Unsupported params tuple schema version: {schema} (expected 0 or 1)")
+
     if not params:
         # Go writes nothing for empty params
         return b""
@@ -98,6 +101,9 @@ def decode_params_tuple(
         buffer_offset: Absolute byte offset where this tuple starts in the
             message body. Used for padding calculation matching Go's behavior.
     """
+    if schema not in (0, 1):
+        raise DecodeError(f"Unsupported params tuple schema version: {schema} (expected 0 or 1)")
+
     # Go writes nothing for empty params
     if len(data) == 0:
         if count is not None and count > 0:

tests/test_tuples.py

@@ -386,6 +386,47 @@ def test_decode_invalid_type_code_raises_decode_error(self) -> None:
             decode_params_tuple(data)
 
 
+class TestParamsTupleSchemaValidation:
+    def test_encode_rejects_schema_2(self) -> None:
+        import pytest
+
+        from dqlitewire.exceptions import EncodeError
+
+        with pytest.raises(EncodeError, match="Unsupported params tuple schema"):
+            encode_params_tuple([42], schema=2)
+
+    def test_encode_rejects_negative_schema(self) -> None:
+        import pytest
+
+        from dqlitewire.exceptions import EncodeError
+
+        with pytest.raises(EncodeError, match="Unsupported params tuple schema"):
+            encode_params_tuple([42], schema=-1)
+
+    def test_decode_rejects_schema_2(self) -> None:
+        import pytest
+
+        from dqlitewire.exceptions import DecodeError
+
+        data = encode_params_tuple([42], schema=0)
+        with pytest.raises(DecodeError, match="Unsupported params tuple schema"):
+            decode_params_tuple(data, schema=2)
+
+    def test_decode_rejects_negative_schema(self) -> None:
+        import pytest
+
+        from dqlitewire.exceptions import DecodeError
+
+        data = encode_params_tuple([42], schema=0)
+        with pytest.raises(DecodeError, match="Unsupported params tuple schema"):
+            decode_params_tuple(data, schema=-1)
+
+    def test_encode_accepts_schema_0_and_1(self) -> None:
+        """Schema 0 and 1 should work normally."""
+        encode_params_tuple([42], schema=0)
+        encode_params_tuple([42], schema=1)
+
+
 class TestParamsTupleErrors:
     def test_decode_insufficient_data_for_header(self) -> None:
         """Data shorter than 8 bytes should raise DecodeError."""