fix(context): harden description checks for bad MDL rows (#2616)

core/wren/src/wren/context.py

@@ -1117,6 +1117,29 @@ def validate_project(project_path: Path) -> list[ValidationError]:
                     )
                 )
 
+        props = model.get("properties")
+        if props is not None and not isinstance(props, dict):
+            errors.append(
+                ValidationError(
+                    "error",
+                    f"{src_path} > {name}",
+                    "properties must be a mapping",
+                )
+            )
+        for j, col in enumerate(columns):
+            if not isinstance(col, dict):
+                continue
+            col_props = col.get("properties")
+            if col_props is not None and not isinstance(col_props, dict):
+                col_name = col.get("name") or f"columns[{j}]"
+                errors.append(
+                    ValidationError(
+                        "error",
+                        f"{src_path} > {name} > {col_name}",
+                        "properties must be a mapping",
+                    )
+                )
+
     # v1 legacy views.yml may contain non-mapping entries (e.g. `- null`).
     # load_views() silently drops those (matching the other loaders), but
     # validate_project's job is to tell the user about hand-edited mistakes
@@ -1232,6 +1255,16 @@ def validate_project(project_path: Path) -> list[ValidationError]:
                     )
                 )
 
+        view_props = view.get("properties")
+        if view_props is not None and not isinstance(view_props, dict):
+            errors.append(
+                ValidationError(
+                    "error",
+                    f"views/{src_dir}",
+                    "properties must be a mapping",
+                )
+            )
+
     # Check relationships — walk the raw list when available so indices match
     # the file (filtered loader positions would renumber past dropped junk).
     all_entity_names = model_names | view_names
@@ -1644,7 +1677,10 @@ _VALID_LEVELS = frozenset({"error", "warning", "strict"})
 
 
 def _prop_description(item: dict) -> str | None:
-    return (item.get("properties") or {}).get("description")
+    props = item.get("properties") or {}
+    if not isinstance(props, dict):
+        return None
+    return props.get("description")
 
 
 def _check_descriptions(manifest: dict, *, strict: bool = False) -> list[str]:

core/wren/tests/unit/test_check_descriptions_guards.py

@@ -0,0 +1,60 @@
+"""Guards for non-mapping properties and safe description lookup."""
+
+from __future__ import annotations
+
+import textwrap
+from pathlib import Path
+
+from wren.context import _prop_description, validate_project
+
+
+def test_prop_description_non_mapping_returns_none():
+    assert _prop_description({"properties": "oops"}) is None
+    assert _prop_description({"properties": {"description": "ok"}}) == "ok"
+    assert _prop_description({}) is None
+
+
+def test_validate_project_reports_non_mapping_properties(tmp_path: Path):
+    (tmp_path / "wren_project.yml").write_text(
+        "name: demo\ndata_source: postgres\nschema_version: 2\n",
+        encoding="utf-8",
+    )
+    model_dir = tmp_path / "models" / "orders"
+    model_dir.mkdir(parents=True)
+    (model_dir / "metadata.yml").write_text(
+        textwrap.dedent(
+            """\
+            name: orders
+            table_reference:
+              table: orders
+            properties: oops
+            columns:
+              - name: id
+                type: INTEGER
+                properties: not-a-map
+            """
+        ),
+        encoding="utf-8",
+    )
+    view_dir = tmp_path / "views" / "v1"
+    view_dir.mkdir(parents=True)
+    (view_dir / "metadata.yml").write_text(
+        textwrap.dedent(
+            """\
+            name: v1
+            properties: []
+            """
+        ),
+        encoding="utf-8",
+    )
+    (view_dir / "sql.yml").write_text(
+        "statement: SELECT 1\n",
+        encoding="utf-8",
+    )
+
+    errors = validate_project(tmp_path)
+    messages = [f"{e.path}: {e.message}" for e in errors]
+    joined = "\n".join(messages)
+    assert "properties must be a mapping" in joined
+    # model + column + view
+    assert sum("properties must be a mapping" in m for m in messages) == 3