refactor: introduce common 'ResourceNotFoundError' exception (#3032)

# What does this PR do?
1. Introduce new base custom exception class `ResourceNotFoundError`
2. All other "not found" exception classes now inherit from
`ResourceNotFoundError`

Closes #3030

Signed-off-by: Nathan Weinberg <nweinber@redhat.com>

llama_stack/apis/common/errors.py

@@ -10,6 +10,16 @@
 #   3. All classes should propogate the inherited __init__ function otherwise via 'super().__init__(message)'
 
 
+class ResourceNotFoundError(ValueError):
+    """generic exception for a missing Llama Stack resource"""
+
+    def __init__(self, resource_name: str, resource_type: str, client_list: str) -> None:
+        message = (
+            f"{resource_type} '{resource_name}' not found. Use '{client_list}' to list available {resource_type}s."
+        )
+        super().__init__(message)
+
+
 class UnsupportedModelError(ValueError):
     """raised when model is not present in the list of supported models"""
 
@@ -18,38 +28,32 @@ class UnsupportedModelError(ValueError):
         super().__init__(message)
 
 
-class ModelNotFoundError(ValueError):
+class ModelNotFoundError(ResourceNotFoundError):
     """raised when Llama Stack cannot find a referenced model"""
 
     def __init__(self, model_name: str) -> None:
-        message = f"Model '{model_name}' not found. Use client.models.list() to list available models."
+        super().__init__(model_name, "Model", "client.models.list()")
-        super().__init__(message)
 
 
-class VectorStoreNotFoundError(ValueError):
+class VectorStoreNotFoundError(ResourceNotFoundError):
     """raised when Llama Stack cannot find a referenced vector store"""
 
     def __init__(self, vector_store_name: str) -> None:
-        message = f"Vector store '{vector_store_name}' not found. Use client.vector_dbs.list() to list available vector stores."
+        super().__init__(vector_store_name, "Vector Store", "client.vector_dbs.list()")
-        super().__init__(message)
 
 
-class DatasetNotFoundError(ValueError):
+class DatasetNotFoundError(ResourceNotFoundError):
     """raised when Llama Stack cannot find a referenced dataset"""
 
     def __init__(self, dataset_name: str) -> None:
-        message = f"Dataset '{dataset_name}' not found. Use client.datasets.list() to list available datasets."
+        super().__init__(dataset_name, "Dataset", "client.datasets.list()")
-        super().__init__(message)
 
 
-class ToolGroupNotFoundError(ValueError):
+class ToolGroupNotFoundError(ResourceNotFoundError):
     """raised when Llama Stack cannot find a referenced tool group"""
 
     def __init__(self, toolgroup_name: str) -> None:
-        message = (
+        super().__init__(toolgroup_name, "Tool Group", "client.toolgroups.list()")
-            f"Tool group '{toolgroup_name}' not found. Use client.toolgroups.list() to list available tool groups."
-        )
-        super().__init__(message)
 
 
 class SessionNotFoundError(ValueError):

tests/integration/tool_runtime/test_registration.py

@@ -4,9 +4,12 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
+import re
+
 import pytest
 
 from llama_stack import LlamaStackAsLibraryClient
+from llama_stack.apis.common.errors import ToolGroupNotFoundError
 from tests.common.mcp import MCP_TOOLGROUP_ID, make_mcp_server
 
 
@@ -48,8 +51,18 @@ def test_register_and_unregister_toolgroup(llama_stack_client):
         llama_stack_client.toolgroups.unregister(toolgroup_id=test_toolgroup_id)
 
         # Verify it is unregistered
-        with pytest.raises(Exception, match=f"Tool group '{test_toolgroup_id}' not found"):
+        with pytest.raises(
+            ToolGroupNotFoundError,
+            match=re.escape(
+                f"Tool Group '{test_toolgroup_id}' not found. Use 'client.toolgroups.list()' to list available Tool Groups."
+            ),
+        ):
             llama_stack_client.toolgroups.get(toolgroup_id=test_toolgroup_id)
 
-        with pytest.raises(Exception, match=f"Tool group '{test_toolgroup_id}' not found"):
+        with pytest.raises(
+            ToolGroupNotFoundError,
+            match=re.escape(
+                f"Tool Group '{test_toolgroup_id}' not found. Use 'client.toolgroups.list()' to list available Tool Groups."
+            ),
+        ):
             llama_stack_client.tools.list(toolgroup_id=test_toolgroup_id)