Fix outdated organization_membership events

[mattgd]

Description

This PR addresses handling of custom_attributes in organization membership events. The field is now defaulted to an empty dict and undefined values from the API are coerced to empty dicts, maintaining type safety without requiring optional fields.

A new event test verifies that organization_membership events with null custom_attributes deserialize correctly.

Documentation

Does this require changes to the WorkOS Docs? E.g. the API Reference or code snippets need updates.

• Yes

[greptile-apps]

Greptile Summary

This PR fixes a deserialization issue where the WorkOS API can return custom_attributes: null in organization membership event payloads, which would cause a Pydantic validation error since the field was typed as Mapping[str, Any] without accepting None.

• Adds a field_validator on OrganizationMembership.custom_attributes to coerce None values to {} before validation, preventing runtime errors when processing events from the API.
• Sets the default value of custom_attributes to {}, making the field optional in the input payload while maintaining the non-optional Mapping[str, Any] type for consumers.
• Adds a targeted test that verifies organization_membership.created events with custom_attributes: None deserialize correctly as {}.

Confidence Score: 5/5

• This PR is safe to merge — it's a minimal, well-tested fix for a real API deserialization issue.
• The change is small, focused, and correct. The field_validator properly handles the None case before Pydantic validation, and the default = {} is safe in Pydantic (which copies defaults). The fix is consistent with how the codebase handles similar nullable fields (e.g., Profile.custom_attributes uses Optional, but OrganizationMembership intentionally avoids exposing None to consumers). The new test directly validates the fix. No security, performance, or correctness concerns.
• No files require special attention

Important Files Changed

Filename	Overview
src/workos/types/user_management/organization_membership.py	Adds a Pydantic field_validator to coerce null custom_attributes to {} and sets the default value to {}. Clean and correct implementation.
tests/test_events.py	Adds a fixture and test for organization membership events with null custom_attributes. Verifies deserialization works correctly and asserts the event type and coerced value.

Sequence Diagram

sequenceDiagram
    participant API as WorkOS API
    participant SDK as Python SDK
    participant Val as field_validator
    participant Model as OrganizationMembership

    API->>SDK: Event payload with custom_attributes: null
    SDK->>Val: _coerce_null_custom_attributes(None)
    Val->>Val: None → {}
    Val->>Model: Validate with custom_attributes = {}
    Model->>SDK: OrganizationMembership(custom_attributes={})

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[greptile-apps]

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[mattgd]

This handles cases for events from before the IdP attributes in AuthKit release where custom_attributes is undefined.