Unexpected response with the verification of the modified Enum class

Example

For string enum generation, there is a convenient way as the Python official docs said:

from enum import Enum,auto
class Enum0(str,Enum):
    def _generate_next_value_(name, start, count, last_values):
        return name
    A = auto()
    B = auto()

And this enum class is equivalent to the following:

class Enum1(str,Enum):
    A = 'A'
    B = 'B'

Both of them work with the below FastAPI code(change type hint to each class before run):

from fastapi import FastAPI

app = FastAPI()
@app.get("/model/{mod}")
async def model(mod:Enum0):
    return {'msg':mod,'val':mod.value}

However, when I write a self-defined enum class like this:

class Enum2(str,Enum):
    def __init__(self):
        self._value_ = self.name
        super().__init__()
    A = ()
    B = ()

It doesn’t work with the previous model(mod) callable.

Description

• Open the browser and call the endpoint /model/A.
• It returns a JSON with {"detail":[{"loc":["path","mod"],"msg":"value is not a valid enumeration member; permitted: 'A', 'B'","type":"type_error.enum","ctx":{"enum_values":["A","B"]}}]}.
• But I expected it to return {"msg":"A","val":"A"}.
• I compared the Enum1 and the Enum2, and can not find any valuable difference.

Environment

• OS: Windows 10 x64, 10.0.19042.630
• FastAPI Version: 0.61.2
• Python Version: 3.8.5 x64

Additional context

• The style of generating enum member like A = () is come from Python docs(enum#using-a-custom-new)

[Mause]

Your Enum2 doesn’t work in pydantic for the same reason the following code doesn’t work without pydantic:

from enum import Enum

class​ ​Enum2​(​str​,​Enum​):
    ​def​ ​__init__​(​self​):
        ​self​.​_value_​ ​=​ ​self​.​name​
        ​super​().​__init__​()
    ​A​ ​=​ ()
    ​B​ ​=​ ()

Enum2('A') # ValueError: 'A' is not a valid Enum2

You could argue that this is a bug in either your code, or a bug in the enum library, but either way it doesn’t work

[Mause]

Do you mean to be doing

A = auto()
B = auto()

Instead?