process_schema() fails for recursive schemas

[azaroth42]

Per https://github.com/googleapis/python-genai/blob/main/google/genai/_transformers.py#L397 the process_schema() function tries to inline all of the $defs in the schema. This generates an infinite recursion for recursive schemas.

Proposal: Provide a maximum_depth configurable parameter that will break out of any infinite loops like this at a certain point.

Environment details

• Programming language: Python
• OS: MacOS
• Language runtime version: 3.12.7
• Package version: github master at 2025-02-27

Steps to reproduce

1. Create a recursive schema in pydantic or json schema, as below
2. Set it as the response_schema in the config
3. Attempt to generate content and observe the infinite recursion error

Observed Behavior:

File "/Users/rs2668/Development/llm/python-genai/./test.py", line 58, in generate
    for chunk in client.models.generate_content_stream(
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/rs2668/Development/llm/python-genai/google/genai/models.py", line 4808, in generate_content_stream
    for chunk in response:
                 ^^^^^^^^
  File "/Users/rs2668/Development/llm/python-genai/google/genai/models.py", line 3864, in _generate_content_stream
    request_dict = _GenerateContentParameters_to_vertex(
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/rs2668/Development/llm/python-genai/google/genai/models.py", line 1190, in _GenerateContentParameters_to_vertex
    _GenerateContentConfig_to_vertex(
  File "/Users/rs2668/Development/llm/python-genai/google/genai/models.py", line 1037, in _GenerateContentConfig_to_vertex
    t.t_schema(api_client, getv(from_object, ['response_schema'])),
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/rs2668/Development/llm/python-genai/google/genai/_transformers.py", line 596, in t_schema
    process_schema(schema, client)
  File "/Users/rs2668/Development/llm/python-genai/google/genai/_transformers.py", line 471, in process_schema
    process_schema(sub_schema, client, defs)
  File "/Users/rs2668/Development/llm/python-genai/google/genai/_transformers.py", line 523, in process_schema
    process_schema(sub_schema, client, defs)
  File "/Users/rs2668/Development/llm/python-genai/google/genai/_transformers.py", line 547, in process_schema
    process_schema(ref, client, defs)
  File "/Users/rs2668/Development/llm/python-genai/google/genai/_transformers.py", line 523, in process_schema
    process_schema(sub_schema, client, defs)
  File "/Users/rs2668/Development/llm/python-genai/google/genai/_transformers.py", line 547, in process_schema
    process_schema(ref, client, defs)
...
RecursionError: maximum recursion depth exceeded

Expected Behavior:

That the schema would be processed

Test Case

Here is a minimal test case that produces the recursion error. I hope that it's clear.

from typing import List
from pydantic import BaseModel
from google import genai
from google.genai import types

class Node(BaseModel):
    name: str
    kids: List['Node']
Node.model_rebuild()

client = genai.Client(
      vertexai=True,
      project=" project name here ",
      location="us-central1",
)

textsi = """
You will be given a hierarchy in text. Please construct a tree of JSON objects.
Each JSON object has a "name" property for the name of the node in the hierarchy, and a "kids" property which is an array of JSON objects.
"""

generated_config = types.GenerateContentConfig(
    response_mime_type = "application/json",
    response_schema = Node,
    system_instruction=[types.Part.from_text(text=textsi)],
)

def generate(prompt):
  contents = [
    types.Content(
      role="user",
      parts=[types.Part.from_text(text=prompt)]
    )
  ]
  output = []
  for chunk in client.models.generate_content_stream(
    model = "gemini-2.0-flash-001",
    contents = contents,
    config = generated_config,
    ):
    output.append(chunk.text)
  return ''.join(output)


prompt = """
* Top
  * Materials
    * Metals
      * Gold
      * Silver
      * Bronze
    * Stone
      * Flint
      * Granite
      * Marble
"""

res = generate(prompt)

Thank you!