TypeError in convert_if_exist_pydantic_model with parameterized generic types

[tobert]

Description

When automatic function calling processes a function with a parameterized generic type annotation (e.g., set[str]), the SDK raises TypeError: isinstance() argument 2 cannot be a parameterized generic.

Note

Apologies, my agent posted before I got to review this, but it seems mostly fine.

Minimal Reproduction

from google.genai._extra_utils import convert_if_exist_pydantic_model

# Simulating what happens when Gemini returns a value for a set[str] parameter
result = convert_if_exist_pydantic_model(
    value=['a', 'b'],           # Gemini returns list (JSON array)
    annotation=set[str],        # But annotation is set[str]
    param_name='items',
    func_name='my_func'
)
# TypeError: isinstance() argument 2 cannot be a parameterized generic

Cause

In _extra_utils.py, the function convert_if_exist_pydantic_model() has two locations where isinstance() is called with an annotation that could be a GenericAlias:

Line 257 (inside Union handling):

or isinstance(value, arg)

Line 279 (final fallback):

if not isinstance(value, annotation):

In Python, isinstance(x, set[str]) raises TypeError because set[str] is a GenericAlias, not a type. The SDK correctly handles list[T] and dict[K,V] with special cases using get_origin(), but other parameterized generics fall through to the raw isinstance() call.

Affected Versions

• google-genai 1.60.0
• google-genai 1.61.0

Environment

• Python 3.12
• Linux

Proposed Fix

Add a helper function that safely handles parameterized generics:

def _safe_isinstance(value: Any, annotation: Any) -> bool:
    """Check isinstance, handling GenericAlias types like set[str]."""
    origin = get_origin(annotation)
    if origin is not None:
        return isinstance(value, origin)
    try:
        return isinstance(value, annotation)
    except TypeError:
        return False

Then replace:

• Line 257: isinstance(value, arg) → _safe_isinstance(value, arg)
• Line 279: isinstance(value, annotation) → _safe_isinstance(value, annotation)

This follows the same pattern already used for list[T] and dict[K,V] at lines 239 and 245.