Fix #2441: get_default_cube_config crashes with UnboundLocalError on invalid text_mem_type

src/memos/mem_os/utils/default_config.py

@@ -14,6 +14,28 @@
 
 logger = logging.getLogger(__name__)
 
+# Text-memory backends that the default-config helpers know how to wire up.
+# Keep in sync with the Literal type hint on text_mem_type below.
+_SUPPORTED_TEXT_MEM_TYPES: tuple[str, ...] = ("tree_text", "general_text")
+
+
+def _validate_text_mem_type(text_mem_type: str) -> None:
+    """Reject unknown text_mem_type values with a clear ValueError.
+
+    The default-config helpers only wire up a handful of text-memory backends
+    (``tree_text`` and ``general_text``). Historically the helper fell through
+    silently when the caller passed anything else — for example a typo like
+    ``"tree-text"`` coming through the ``MOS_TEXT_MEM_TYPE`` env var or the
+    MCP ``create_cube`` path — and crashed with a bare ``UnboundLocalError``.
+
+    See issue #2441.
+    """
+    if text_mem_type not in _SUPPORTED_TEXT_MEM_TYPES:
+        supported = ", ".join(repr(t) for t in _SUPPORTED_TEXT_MEM_TYPES)
+        raise ValueError(
+            f"Unsupported text_mem_type={text_mem_type!r}. Expected one of: {supported}."
+        )
+
 
 def get_default_config(
     openai_api_key: str,
@@ -45,6 +67,10 @@ def get_default_config(
         mos = MOS(config)
         ```
     """
+    # Validate up front so both MOS and MemCube helpers fail with the same
+    # clear error when the caller (or an env var like MOS_TEXT_MEM_TYPE) hands
+    # in a typo. See issue #2441.
+    _validate_text_mem_type(text_mem_type)
 
     # Base OpenAI configuration
     openai_config = {
@@ -148,6 +174,9 @@ def get_default_cube_config(
     Returns:
         GeneralMemCubeConfig: Complete MemCube configuration object
     """
+    # Fail fast on invalid backends so the caller sees a clear error instead of
+    # an UnboundLocalError deeper in the function (issue #2441).
+    _validate_text_mem_type(text_mem_type)
 
     # Base OpenAI configuration
     openai_config = {
@@ -230,6 +259,14 @@ def get_default_cube_config(
                 "embedder": embedder_config,
             },
         }
+    else:
+        # Defensive: _validate_text_mem_type above rejects anything else, but
+        # keep an explicit branch so future refactors cannot silently reintroduce
+        # the UnboundLocalError this file used to raise (issue #2441).
+        raise ValueError(
+            f"Unsupported text_mem_type={text_mem_type!r}. "
+            f"Expected one of: {', '.join(repr(t) for t in _SUPPORTED_TEXT_MEM_TYPES)}."
+        )
 
     # Configure activation memory if enabled.
     # KV cache activation memory requires a local HuggingFace/vLLM model (it

tests/mem_os/utils/test_default_config.py

@@ -0,0 +1,102 @@
+"""Test suite for src/memos/mem_os/utils/default_config.py.
+
+Focus: get_default_cube_config / get_default_config defensive behavior
+when the caller passes an unknown text_mem_type value.
+
+Related issue: #2441.
+"""
+
+import pytest
+
+from memos.mem_os.utils.default_config import (
+    get_default_config,
+    get_default_cube_config,
+)
+
+
+class TestGetDefaultCubeConfigInvalidTextMemType:
+    """`get_default_cube_config` must raise a clear ValueError, not UnboundLocalError."""
+
+    def test_invalid_text_mem_type_raises_value_error(self):
+        """Passing a typo like 'tree-text' must raise ValueError (issue #2441)."""
+        with pytest.raises(ValueError) as exc_info:
+            get_default_cube_config(
+                openai_api_key="sk-test",
+                text_mem_type="tree-text",  # typo, should not crash silently
+            )
+
+        message = str(exc_info.value)
+        # Error must name the offending value so operators can find their typo fast.
+        assert "tree-text" in message
+        # Error must list the accepted values so callers know what to use.
+        assert "tree_text" in message
+        assert "general_text" in message
+
+    def test_invalid_text_mem_type_does_not_leak_unbound_local(self):
+        """The old bug (issue #2441) raised UnboundLocalError; guard against regression."""
+        with pytest.raises(ValueError):
+            get_default_cube_config(
+                openai_api_key="sk-test",
+                text_mem_type="totally_unknown_backend",
+            )
+
+    def test_empty_text_mem_type_raises_value_error(self):
+        """Empty string should also fail loudly, not fall through to UnboundLocalError."""
+        with pytest.raises(ValueError):
+            get_default_cube_config(
+                openai_api_key="sk-test",
+                text_mem_type="",  # type: ignore[arg-type]
+            )
+
+
+class TestGetDefaultConfigInvalidTextMemType:
+    """`get_default_config` accepts the same text_mem_type parameter and should
+    validate it symmetrically so both entry points fail with the same clear error
+    when they receive garbage input.
+
+    ``get_default_config`` and ``get_default_cube_config`` each call
+    ``_validate_text_mem_type`` independently (they do not share a delegation
+    path), so we mirror the same three regression cases here — a typo, an
+    unknown backend name, and the empty string — to keep coverage symmetric
+    across both entry points for issue #2441.
+    """
+
+    def test_invalid_text_mem_type_raises_value_error(self):
+        with pytest.raises(ValueError) as exc_info:
+            get_default_config(
+                openai_api_key="sk-test",
+                text_mem_type="tree-text",
+            )
+
+        message = str(exc_info.value)
+        assert "tree-text" in message
+        assert "tree_text" in message
+        assert "general_text" in message
+
+    def test_invalid_text_mem_type_does_not_leak_unbound_local(self):
+        """Unknown backend names must fail with ValueError, not UnboundLocalError."""
+        with pytest.raises(ValueError):
+            get_default_config(
+                openai_api_key="sk-test",
+                text_mem_type="totally_unknown_backend",
+            )
+
+    def test_empty_text_mem_type_raises_value_error(self):
+        """Empty string should also fail loudly, symmetric with the cube helper."""
+        with pytest.raises(ValueError):
+            get_default_config(
+                openai_api_key="sk-test",
+                text_mem_type="",  # type: ignore[arg-type]
+            )
+
+
+class TestGetDefaultCubeConfigValidTextMemType:
+    """Valid values continue to build a MemCube config end-to-end."""
+
+    def test_general_text_still_builds(self):
+        cfg = get_default_cube_config(
+            openai_api_key="sk-test",
+            text_mem_type="general_text",
+            user_id="issue2441_user",
+        )
+        assert cfg.text_mem.backend == "general_text"