Bug: Multiple fields in in_fields configuration cause filter providers to malfunction

[SinoptikInc]

Description

Description

When configuring multiple fields in the in_fields array within create_service_dependencies(), only the last field in the array generates working filter providers. All previous fields fail to create proper CollectionFilter instances due to a closure variable capture issue in the loop.

Environment

• advanced-alchemy version: 1.4.5
• Python version: 3.12
• Framework: Litestar

Expected Behavior

All fields specified in in_fields should generate working filter providers that can be used via query parameters like fieldNameIn=value1,value2.

Actual Behavior

Only the last field in the in_fields array works correctly. Previous fields don't generate any CollectionFilter instances in the filters list, causing the filtering to be ignored.

Reproduction Steps

1. Configure a controller with multiple fields in in_fields:

dependencies = providers.create_service_dependencies(
    MyService,
    "my_service",
    filters={
        "in_fields": [
            providers.FieldNameType("type", str),
            providers.FieldNameType("status", str),
        ],
    },
)

2. Make a request with the first field filter: GET /api/endpoint?typeIn=value
3. Observe that no CollectionFilter is generated for the type field
4. Make a request with the last field filter: GET /api/endpoint?statusIn=value
5. Observe that CollectionFilter works correctly for the status field

Root Cause Analysis

The issue is located in providers.py around lines 516-520:

for field_def in in_fields:
    field_def = FieldNameType(name=field_def, type_hint=str) if isinstance(field_def, str) else field_def

    def create_in_filter_provider(
        field_name: FieldNameType,
    ) -> Callable[..., Optional[CollectionFilter[field_def.type_hint]]]:  # ← Problem here

The closure captures the loop variable field_def by reference, not by value. When the loop completes, all created functions reference the last value of field_def, causing previous fields to malfunction.

Workaround

Currently using manual providers for additional fields:

def status_filter_provider(statusIn: list[str] | None = None) -> filters.CollectionFilter:
    return filters.CollectionFilter(field_name="status", values=statusIn)

dependencies = providers.create_service_dependencies(
    MyService,
    "my_service", 
    filters={
        "in_fields": [
            providers.FieldNameType("type", str),  # Only one field works
        ],
    },
) | {
    "status_filter": status_filter_provider,  # Manual workaround
}

Suggested Fix

The closure should capture the loop variable by value, for example by passing it as a default parameter:

def create_in_filter_provider(
    field_name: FieldNameType = field_def,  # Capture by value
) -> Callable[..., Optional[CollectionFilter]]:

Or restructure the function creation to avoid the closure issue entirely.

Additional Notes

• The same issue likely affects not_in_fields configuration as well
• Single field in in_fields works correctly
• This is a classic Python closure gotcha that affects any loop creating functions with references to loop variables

URL to code causing the issue

No response

MCVE

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Logs

Package Version

advanced-alchemy version: 1.4.5

Platform

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