fix: handle corrupted registry in list() methods

- Add defensive handling to list() when presets/extensions is not a dict
- Return empty dict instead of crashing on corrupted registry
- Apply same fix to both PresetRegistry and ExtensionRegistry for parity
- Add tests for corrupted registry handling

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: iamaeroplane

src/specify_cli/extensions.py

@@ -340,9 +340,12 @@ def list(self) -> Dict[str, dict]:
         from accidentally mutating nested internal registry state.
 
         Returns:
-            Dictionary of extension_id -> metadata (deep copies)
+            Dictionary of extension_id -> metadata (deep copies), empty dict if corrupted
         """
-        return copy.deepcopy(self.data["extensions"])
+        extensions = self.data.get("extensions", {}) or {}
+        if not isinstance(extensions, dict):
+            return {}
+        return copy.deepcopy(extensions)
 
     def is_installed(self, extension_id: str) -> bool:
         """Check if extension is installed.

src/specify_cli/presets.py

@@ -350,9 +350,12 @@ def list(self) -> Dict[str, dict]:
         from accidentally mutating nested internal registry state.
 
         Returns:
-            Dictionary of pack_id -> metadata (deep copies)
+            Dictionary of pack_id -> metadata (deep copies), empty dict if corrupted
         """
-        return copy.deepcopy(self.data["presets"])
+        packs = self.data.get("presets", {}) or {}
+        if not isinstance(packs, dict):
+            return {}
+        return copy.deepcopy(packs)
 
     def list_by_priority(self, include_disabled: bool = False) -> List[tuple]:
         """Get all installed presets sorted by priority.

tests/test_extensions.py

@@ -520,6 +520,20 @@ def test_list_returns_deep_copy(self, temp_dir):
         internal = registry.data["extensions"]["test-ext"]
         assert internal["registered_commands"] == {"claude": ["cmd1"]}
 
+    def test_list_returns_empty_dict_for_corrupted_registry(self, temp_dir):
+        """Test that list() returns empty dict when extensions is not a dict."""
+        extensions_dir = temp_dir / "extensions"
+        extensions_dir.mkdir()
+        registry = ExtensionRegistry(extensions_dir)
+
+        # Corrupt the registry - extensions is a list instead of dict
+        registry.data["extensions"] = ["not", "a", "dict"]
+        registry._save()
+
+        # list() should return empty dict, not crash
+        result = registry.list()
+        assert result == {}
+
 
 # ===== ExtensionManager Tests =====
 

tests/test_presets.py

@@ -487,6 +487,20 @@ def test_list_returns_deep_copy(self, temp_dir):
         assert fresh["version"] == "1.0.0"
         assert fresh["nested"]["key"] == "original"
 
+    def test_list_returns_empty_dict_for_corrupted_registry(self, temp_dir):
+        """Test that list() returns empty dict when presets is not a dict."""
+        packs_dir = temp_dir / "packs"
+        packs_dir.mkdir()
+        registry = PresetRegistry(packs_dir)
+
+        # Corrupt the registry - presets is a list instead of dict
+        registry.data["presets"] = ["not", "a", "dict"]
+        registry._save()
+
+        # list() should return empty dict, not crash
+        result = registry.list()
+        assert result == {}
+
     def test_list_by_priority_excludes_disabled(self, temp_dir):
         """Test that list_by_priority excludes disabled presets by default."""
         packs_dir = temp_dir / "packs"