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Bug Report: Incorrect Model Reference in Generated Paginated Envelope #1390

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Bug Report: Incorrect Model Reference in Generated Paginated Envelope#1390

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Description

thekashifmalik

opened

on Jan 28, 2026

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Bug Report: Incorrect Model Reference in Generated Paginated Envelope

Summary

openapi-python-client incorrectly generates PaginatedTransactionEnvelope with CustomerEntity instead of TransactionEntity, despite the OpenAPI schema correctly specifying TransactionEntity.

Environment

openapi-python-client version: 0.28.1
Python version: 3.13

Generation command:

openapi-python-client generate \
    --path schema.yaml \
    --output-path ./generated \
    --meta none

Expected Behavior

The generated PaginatedTransactionEnvelope should use TransactionEntity based on this schema definition:

PaginatedTransactionEnvelope:
  allOf:
  - $ref: '#/components/schemas/PaginatedSuccessEnvelope'
  - type: object
    properties:
      data:
        type: array
        items:
          $ref: '#/components/schemas/TransactionEntity'

Expected generated code:

if TYPE_CHECKING:
    from ..models.transaction_entity import TransactionEntity
    from ..models.links import Links

@_attrs_define
class PaginatedTransactionEnvelope:
    timestamp: datetime.datetime
    path: str
    data: list[TransactionEntity]  # ✓ Correct
    links: Links

Actual Behavior

The generator produces code using CustomerEntity instead:

if TYPE_CHECKING:
    from ..models.customer_entity import CustomerEntity  # ✗ Wrong!
    from ..models.links import Links

@_attrs_define
class PaginatedTransactionEnvelope:
    timestamp: datetime.datetime
    path: str
    data: list[CustomerEntity]  # ✗ Wrong!
    links: Links
    
@classmethod
def from_dict(cls: type[T], src_dict: Mapping[str, Any]) -> T:
    from ..models.customer_entity import CustomerEntity  # ✗ Wrong!
    from ..models.links import Links
    
    # ...
    for data_item_data in _data:
        data_item = CustomerEntity.from_dict(data_item_data)  # ✗ Wrong!
        data.append(data_item)

Impact

This causes runtime errors when parsing API responses:

ValueError: 'failed' is not a valid CustomerEntityStatus

The parser attempts to deserialize transaction data as customer data, failing when transaction-specific status values don't exist in the CustomerEntityStatus enum.

Additional Context

The schema also defines PaginatedCustomerEnvelope (which correctly uses CustomerEntity). The generator may be incorrectly reusing or caching the entity type across similar paginated envelope structures.

Related schema definitions:

PaginatedCustomerEnvelope:
  allOf:
  - $ref: '#/components/schemas/PaginatedSuccessEnvelope'
  - type: object
    properties:
      data:
        type: array
        items:
          $ref: '#/components/schemas/CustomerEntity'

PaginatedTransactionEnvelope:
  allOf:
  - $ref: '#/components/schemas/PaginatedSuccessEnvelope'
  - type: object
    properties:
      data:
        type: array
        items:
          $ref: '#/components/schemas/TransactionEntity'

Workaround

We've added a post-generation fix script:

sed -i '' 's/from ..models.customer_entity import CustomerEntity/from ..models.transaction_entity import TransactionEntity/g' "$FILE"
sed -i '' 's/list\[CustomerEntity\]/list[TransactionEntity]/g' "$FILE"
sed -i '' 's/CustomerEntity\.from_dict/TransactionEntity.from_dict/g' "$FILE"

Reproduction

The issue appears when:

Multiple paginated envelopes are defined using allOf with shared base schemas
Each envelope should use different entity types in the data array
The generator confuses the entity types between envelopes

Reacted by Mirabis and Piotr Nowiński

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