fix(client): add type guards for direction and max_depth in traverse()

Passing direction=None raised AttributeError; passing max_depth='2' or
max_depth=True raised TypeError. Both now raise ValueError consistently,
matching the documented intent of the validation block.

  - isinstance(direction, str) check before .lower() call
  - isinstance(max_depth, int) and not isinstance(max_depth, bool) before < 1
  - Three new unit tests cover None direction, str max_depth, bool max_depth

Addresses review thread #29.

Author: polaz

coordinode/coordinode/client.py

@@ -385,12 +385,16 @@ async def traverse(
         """
         # Validate pure string/int inputs before importing proto stubs — ensures ValueError
         # is raised even when proto stubs have not been generated yet.
+        # Type guards come first so that wrong types raise ValueError, not AttributeError/TypeError.
+        if not isinstance(direction, str):
+            raise ValueError(f"direction must be a str, got {type(direction).__name__!r}.")
         _valid_directions = {"outbound", "inbound", "both"}
         key = direction.lower()
         if key not in _valid_directions:
             raise ValueError(f"Invalid direction {direction!r}. Must be one of: 'outbound', 'inbound', 'both'.")
-        if max_depth < 1:
-            raise ValueError(f"max_depth must be >= 1, got {max_depth!r}.")
+        # bool is a subclass of int in Python, so `isinstance(True, int)` is True — exclude it.
+        if not isinstance(max_depth, int) or isinstance(max_depth, bool) or max_depth < 1:
+            raise ValueError(f"max_depth must be an integer >= 1, got {max_depth!r}.")
 
         from coordinode._proto.coordinode.v1.graph.graph_pb2 import (  # type: ignore[import]
             TraversalDirection,

tests/unit/test_schema_crud.py

@@ -221,7 +221,37 @@ def test_max_depth_below_one_raises(self):
 
         async def _inner() -> None:
             client = AsyncCoordinodeClient("localhost:0")
-            with pytest.raises(ValueError, match="max_depth must be >= 1"):
+            with pytest.raises(ValueError, match="max_depth must be"):
                 await client.traverse(1, "KNOWS", max_depth=0)
 
         asyncio.run(_inner())
+
+    def test_direction_none_raises_value_error(self):
+        """traverse() raises ValueError (not AttributeError) when direction is None."""
+
+        async def _inner() -> None:
+            client = AsyncCoordinodeClient("localhost:0")
+            with pytest.raises(ValueError, match="direction must be a str"):
+                await client.traverse(1, "KNOWS", direction=None)  # type: ignore[arg-type]
+
+        asyncio.run(_inner())
+
+    def test_max_depth_string_raises_value_error(self):
+        """traverse() raises ValueError (not TypeError) when max_depth is a string."""
+
+        async def _inner() -> None:
+            client = AsyncCoordinodeClient("localhost:0")
+            with pytest.raises(ValueError, match="max_depth must be an integer"):
+                await client.traverse(1, "KNOWS", max_depth="2")  # type: ignore[arg-type]
+
+        asyncio.run(_inner())
+
+    def test_max_depth_bool_raises_value_error(self):
+        """traverse() raises ValueError for bool max_depth (bool is a subclass of int in Python)."""
+
+        async def _inner() -> None:
+            client = AsyncCoordinodeClient("localhost:0")
+            with pytest.raises(ValueError, match="max_depth must be an integer"):
+                await client.traverse(1, "KNOWS", max_depth=True)  # type: ignore[arg-type]
+
+        asyncio.run(_inner())