mistral[patch]: translate tool call IDs to mistral compatible format (#24668)

Mistral appears to have added validation for the format of its tool call
IDs:

`{"object":"error","message":"Tool call id was abc123 but must be a-z,
A-Z, 0-9, with a length of
9.","type":"invalid_request_error","param":null,"code":null}`

This breaks compatibility of messages from other providers. Here we add
a function that converts any string to a Mistral-valid tool call ID, and
apply it to incoming messages.

libs/partners/mistralai/langchain_mistralai/chat_models.py

@@ -1,7 +1,9 @@
 from __future__ import annotations
 
+import hashlib
 import json
 import logging
+import re
 import uuid
 from operator import itemgetter
 from typing import (
@@ -77,6 +79,9 @@ from langchain_core.utils.pydantic import is_basemodel_subclass
 
 logger = logging.getLogger(__name__)
 
+# Mistral enforces a specific pattern for tool call IDs
+TOOL_CALL_ID_PATTERN = re.compile(r"^[a-zA-Z0-9]{9}$")
+
 
 def _create_retry_decorator(
     llm: ChatMistralAI,
@@ -92,6 +97,39 @@ def _create_retry_decorator(
     )
 
 
+def _is_valid_mistral_tool_call_id(tool_call_id: str) -> bool:
+    """Check if tool call ID is nine character string consisting of a-z, A-Z, 0-9"""
+    return bool(TOOL_CALL_ID_PATTERN.match(tool_call_id))
+
+
+def _base62_encode(num: int) -> str:
+    """Encodes a number in base62 and ensures result is of a specified length."""
+    base62 = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+    if num == 0:
+        return base62[0]
+    arr = []
+    base = len(base62)
+    while num:
+        num, rem = divmod(num, base)
+        arr.append(base62[rem])
+    arr.reverse()
+    return "".join(arr)
+
+
+def _convert_tool_call_id_to_mistral_compatible(tool_call_id: str) -> str:
+    """Convert a tool call ID to a Mistral-compatible format"""
+    if _is_valid_mistral_tool_call_id(tool_call_id):
+        return tool_call_id
+    else:
+        hash_bytes = hashlib.sha256(tool_call_id.encode()).digest()
+        hash_int = int.from_bytes(hash_bytes, byteorder="big")
+        base62_str = _base62_encode(hash_int)
+        if len(base62_str) >= 9:
+            return base62_str[:9]
+        else:
+            return base62_str.rjust(9, "0")
+
+
 def _convert_mistral_chat_message_to_message(
     _message: Dict,
 ) -> BaseMessage:
@@ -246,7 +284,7 @@ def _format_tool_call_for_mistral(tool_call: ToolCall) -> dict:
         }
     }
     if _id := tool_call.get("id"):
-        result["id"] = _id
+        result["id"] = _convert_tool_call_id_to_mistral_compatible(_id)
 
     return result
 
@@ -260,7 +298,7 @@ def _format_invalid_tool_call_for_mistral(invalid_tool_call: InvalidToolCall) ->
         }
     }
     if _id := invalid_tool_call.get("id"):
-        result["id"] = _id
+        result["id"] = _convert_tool_call_id_to_mistral_compatible(_id)
 
     return result