如何为使用pydantic的数据集列表生成JSON模式？

Question

我正在尝试从python数据类生成JSON，这些类包含作为参数的其他数据类的列表。除了生成json模式之外，我并不真正关心pydantic的任何功能，因为我只是使用输出来自动生成web前端。因此，使用其他库的解决方案是可以的。

from typing import List
from dataclasses import dataclass
import pydantic

@dataclass()
class SomeParameters:
    a: int = 5

@dataclass()
class SomeMoreParameters:
    another: List[SomeParameters]

pydantic_cls = pydantic.dataclasses.dataclass(SomeMoreParameters)
schema = pydantic_cls.__pydantic_model__.schema()

下面的堆栈跟踪出现了以下代码错误(您可以使用SKIP_CYTHON=1 pip install --no-cache-dir --no-binary :all: pydantic安装pydantic，以便调试到其中)：

Traceback (most recent call last):
  File "/home/veith/Projects/job-ui-parametrization/debug.py", line 17, in <module>
    schema = pydantic_cls.__pydantic_model__.schema()
  File "/home/veith/Projects/job-ui-parametrization/venv/lib/python3.9/site-packages/pydantic/main.py", line 647, in schema
    s = model_schema(cls, by_alias=by_alias, ref_template=ref_template)
  File "/home/veith/Projects/job-ui-parametrization/venv/lib/python3.9/site-packages/pydantic/schema.py", line 185, in model_schema
    m_schema, m_definitions, nested_models = model_process_schema(
  File "/home/veith/Projects/job-ui-parametrization/venv/lib/python3.9/site-packages/pydantic/schema.py", line 617, in model_process_schema
    m_schema, m_definitions, nested_models = model_type_schema(
  File "/home/veith/Projects/job-ui-parametrization/venv/lib/python3.9/site-packages/pydantic/schema.py", line 658, in model_type_schema
    f_schema, f_definitions, f_nested_models = field_schema(
  File "/home/veith/Projects/job-ui-parametrization/venv/lib/python3.9/site-packages/pydantic/schema.py", line 258, in field_schema
    f_schema, f_definitions, f_nested_models = field_type_schema(
  File "/home/veith/Projects/job-ui-parametrization/venv/lib/python3.9/site-packages/pydantic/schema.py", line 498, in field_type_schema
    items_schema, f_definitions, f_nested_models = field_singleton_schema(
  File "/home/veith/Projects/job-ui-parametrization/venv/lib/python3.9/site-packages/pydantic/schema.py", line 848, in field_singleton_schema
    return field_singleton_sub_fields_schema(
  File "/home/veith/Projects/job-ui-parametrization/venv/lib/python3.9/site-packages/pydantic/schema.py", line 736, in field_singleton_sub_fields_schema
    return field_type_schema(
  File "/home/veith/Projects/job-ui-parametrization/venv/lib/python3.9/site-packages/pydantic/schema.py", line 563, in field_type_schema
    f_schema, f_definitions, f_nested_models = field_singleton_schema(
  File "/home/veith/Projects/job-ui-parametrization/venv/lib/python3.9/site-packages/pydantic/schema.py", line 947, in field_singleton_schema
    raise ValueError(f'Value not declarable with JSON Schema, field: {field}')
ValueError: Value not declarable with JSON Schema, field: name='_another' type=SomeParameters required=True

Process finished with exit code 1

现在，根据JSON模式文档，一个事物数组是有效的。脓性文献使用整数列表，这也适用于我。我希望我也可以在列表中使用自定义类型。文档进一步声明了Nested dataclasses are supported both in dataclasses and normal models.

我做错了什么/没有做我应该做的事情吗？还是我误会了，这是不允许的？如果是这样的话，还有什么可供选择的？

Answer 1

这是一个错误引入了脓性1.9。我提供了一个拉请求来解决这个问题：https://github.com/samuelcolvin/pydantic/pull/3819

Answer 2

有趣的是，您的代码在Python3.9.1 (Windows)上为我工作。只是好奇，您使用的是什么版本的pydantic？

这是对我有用的代码。注意，您可以使用pydantic插入数据来稍微简化JSON模式的生成。

from typing import List
# from dataclasses import dataclass
from pydantic.dataclasses import dataclass

@dataclass
class SomeParameters:
    a: int = 5

@dataclass
class SomeMoreParameters:
    another: List[SomeParameters]

# pydantic_cls = pydantic.dataclasses.dataclass(SomeMoreParameters)
schema = SomeMoreParameters.__pydantic_model__.schema()
print(schema)

输出：

{'title': 'SomeMoreParameters', 'type': 'object', 'properties': {'another': {'title': 'Another', 'type': 'array', 'items': {'$ref': '#/definitions/SomeParameters'}}}, 'required': ['another'], 'definitions': {'SomeParameters': {'title': 'SomeParameters', 'type': 'object', 'properties': {'a': {'title': 'A', 'default': 5, 'type': 'integer'}}}}}

注意:我使用的是pydantic==1.8.2。