Recursion errors for self-referencing generic models #1345
Description
Question
Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":
pydantic version: 1.4
pydantic compiled: False
install path: F:\Software\Miniconda3\Lib\site-packages\pydantic
python version: 3.7.6 | packaged by conda-forge | (default, Jan 7 2020, 21:48:41) [MSC v.1916 64 bit (AMD64)]
platform: Windows-10-10.0.18362-SP0
optional deps. installed: []
Issue
I wrote a generic model named Tree as shown in the following snippet.
from __future__ import annotations
from pydantic import BaseModel, Schema
from typing import List, Generic, TypeVar
from pydantic.generics import GenericModel
T = TypeVar('T')
class Node(GenericModel, Generic[T]):
value: T = Schema(..., description = 'Node value')
children: List[Node[T]] = Schema([], description = 'Node children')
Node.update_forward_refs()
class Tree(GenericModel, Generic[T]):
nodes: List[Node[T]] = Schema([], description = 'Top level nodes')I get the error "maximum recursion depth exceeded while calling a Python object" when I try to use it. Any suggestions on how I can fix this would be greatly appreciated.
If I modify the Node.children type from List[Node[T]] to List[Node], then the error disappers.
from __future__ import annotations
from pydantic import BaseModel, Schema
from typing import List, Generic, TypeVar
from pydantic.generics import GenericModel
T = TypeVar('T')
class Node(GenericModel, Generic[T]):
value: T = Schema(..., description = 'Node value')
children: List[Node] = Schema([], description = 'Node children')
Node.update_forward_refs()
class Tree(GenericModel, Generic[T]):
nodes: List[Node[T]] = Schema([], description = 'Top level nodes')The problem in this case is that, it accepts any Node type as the children as shown in the following code.
n1 = Node[str](value = "j")
n2 = Node[int](value = 2)
n0 = Node[int](value = 0, children = [n1, n2])
Tree[int](nodes = [n0]).dict()I want it to support only Node[int] as children, and I want it throw a validation error in the above case.