fix(presets): reject falsy non-mapping catalog config shapes

src/specify_cli/presets/__init__.py

@@ -4292,22 +4292,37 @@ def _load_catalog_config(self, config_path: Path) -> Optional[List[PresetCatalog
         if not config_path.exists():
             return None
         try:
-            data = yaml.safe_load(config_path.read_text(encoding="utf-8")) or {}
+            data = yaml.safe_load(config_path.read_text(encoding="utf-8"))
         except (yaml.YAMLError, OSError, UnicodeError) as e:
             raise PresetValidationError(
                 f"Failed to read catalog config {config_path}: {e}"
             )
+        # Do NOT coerce with ``or {}`` here: that also turns a FALSY
+        # non-mapping top level (``[]``, ``false``, ``0``, ``''``) into ``{}``
+        # and silently swallows it, while a TRUTHY non-mapping (``5``, a bare
+        # list) correctly raises below. Only an empty document/explicit
+        # ``null`` means "no document".
+        if data is None:
+            return None
         if not isinstance(data, dict):
             raise PresetValidationError(
                 f"Invalid catalog config {config_path}: expected a mapping at root, got {type(data).__name__}"
             )
-        catalogs_data = data.get("catalogs", [])
-        if not catalogs_data:
+        # Same asymmetry one nesting level down: the shape check has to run
+        # BEFORE the emptiness check, or a FALSY non-list ``catalogs`` value
+        # (``{}``, ``''``, ``0``, ``false``) is silently swallowed as "no
+        # catalogs" while a TRUTHY non-list (``catalogs: "not-a-list"``)
+        # correctly raises. An absent key or an explicit ``catalogs: null``
+        # both keep their existing "nothing configured here" behavior.
+        catalogs_data = data.get("catalogs")
+        if catalogs_data is None:
             return None
         if not isinstance(catalogs_data, list):
             raise PresetValidationError(
                 f"Invalid catalog config: 'catalogs' must be a list, got {type(catalogs_data).__name__}"
             )
+        if not catalogs_data:
+            return None
         entries: List[PresetCatalogEntry] = []
         for idx, item in enumerate(catalogs_data):
             if not isinstance(item, dict):

tests/test_presets.py

@@ -3412,6 +3412,31 @@ def test_load_catalog_config_not_a_list(self, project_dir):
         with pytest.raises(PresetValidationError, match="must be a list"):
             catalog._load_catalog_config(config_path)
 
+    @pytest.mark.parametrize("body", ["[]\n", "false\n", "0\n", "''\n"])
+    def test_load_catalog_config_rejects_falsy_non_mapping_root(self, project_dir, body):
+        """A FALSY non-mapping top-level config ([], false, 0, '') must raise,
+        like a truthy non-mapping (a bare string) already does. The previous
+        ``yaml.safe_load(...) or {}`` coerced these to {} and silently
+        swallowed them, diverging from the truthy case."""
+        config_path = project_dir / ".specify" / "preset-catalogs.yml"
+        config_path.write_text(body, encoding="utf-8")
+
+        catalog = PresetCatalog(project_dir)
+        with pytest.raises(PresetValidationError, match="expected a mapping"):
+            catalog._load_catalog_config(config_path)
+
+    @pytest.mark.parametrize("body", ["catalogs: {}\n", "catalogs: ''\n", "catalogs: 0\n", "catalogs: false\n"])
+    def test_load_catalog_config_rejects_falsy_non_list_catalogs(self, project_dir, body):
+        """A FALSY non-list ``catalogs:`` value must raise, like a truthy one
+        (``catalogs: "not-a-list"``) already does. The shape check sat behind
+        the emptiness check, so these were silently swallowed as "no catalogs"."""
+        config_path = project_dir / ".specify" / "preset-catalogs.yml"
+        config_path.write_text(body, encoding="utf-8")
+
+        catalog = PresetCatalog(project_dir)
+        with pytest.raises(PresetValidationError, match="must be a list"):
+            catalog._load_catalog_config(config_path)
+
     def test_load_catalog_config_invalid_entry(self, project_dir):
         """Test that non-dict entry raises error."""
         config_path = project_dir / ".specify" / "preset-catalogs.yml"