Fix JSON serialization error in Ollama models (#1129)

* fixing #1128

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* simplify impl and verify dict() requires no args

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: David L. Qiu <david@qiu.dev>

Author: 3 people

packages/jupyter-ai/jupyter_ai/callback_handlers/metadata.py

@@ -1,7 +1,31 @@
+import inspect
+import json
+
 from langchain_core.callbacks import BaseCallbackHandler
 from langchain_core.outputs import LLMResult
 
 
+def requires_no_arguments(func):
+    sig = inspect.signature(func)
+    for param in sig.parameters.values():
+        if param.default is param.empty and param.kind in (
+            param.POSITIONAL_ONLY,
+            param.POSITIONAL_OR_KEYWORD,
+            param.KEYWORD_ONLY,
+        ):
+            return False
+    return True
+
+
+def convert_to_serializable(obj):
+    """Convert an object to a JSON serializable format"""
+    if hasattr(obj, "dict") and callable(obj.dict) and requires_no_arguments(obj.dict):
+        return obj.dict()
+    if hasattr(obj, "__dict__"):
+        return obj.__dict__
+    return str(obj)
+
+
 class MetadataCallbackHandler(BaseCallbackHandler):
     """
     When passed as a callback handler, this stores the LLMResult's
@@ -23,4 +47,9 @@ def on_llm_end(self, response: LLMResult, **kwargs) -> None:
         if not (len(response.generations) and len(response.generations[0])):
             return
 
-        self.jai_metadata = response.generations[0][0].generation_info or {}
+        metadata = response.generations[0][0].generation_info or {}
+
+        # Convert any non-serializable objects in metadata
+        self.jai_metadata = json.loads(
+            json.dumps(metadata, default=convert_to_serializable)
+        )

packages/jupyter-ai/jupyter_ai/models.py

@@ -1,3 +1,4 @@
+import json
 from typing import Any, Dict, List, Literal, Optional, Union
 
 from jupyter_ai_magics import Persona
@@ -128,6 +129,15 @@ class AgentStreamChunkMessage(BaseModel):
     on `BaseAgentMessage.metadata` for information.
     """
 
+    @validator("metadata")
+    def validate_metadata(cls, v):
+        """Ensure metadata values are JSON serializable"""
+        try:
+            json.dumps(v)
+            return v
+        except TypeError as e:
+            raise ValueError(f"Metadata must be JSON serializable: {str(e)}")
+
 
 class HumanChatMessage(BaseModel):
     type: Literal["human"] = "human"