from fastapi.security import OAuth2, OAuth2PasswordRequestFormStrict
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

reusable_oauth2 = OAuth2(
    flows={
        "password": {
            "tokenUrl": "token",
            "scopes": {"read:users": "Read the users", "write:users": "Create users"},
        }
    },
    auto_error=False,
)

from fastapi.security import OAuth2, OAuth2PasswordRequestFormStrict
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

reusable_oauth2 = OAuth2(
    flows={
        "password": {
            "tokenUrl": "token",
            "scopes": {"read:users": "Read the users", "write:users": "Create users"},
        }
    }
)


class User(BaseModel):
    username: str

from fastapi.security import OAuth2, OAuth2PasswordRequestFormStrict
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

reusable_oauth2 = OAuth2(
    flows={
        "password": {
            "tokenUrl": "token",
            "scopes": {"read:users": "Read the users", "write:users": "Create users"},
        }
    },
    description="OAuth2 security scheme",

                }
            }
        },
        "components": {
            "securitySchemes": {
                "OAuth2PasswordBearer": {
                    "type": "oauth2",
                    "flows": {"password": {"scopes": {}, "tokenUrl": "token"}},
                }
            },
        },

                    },
                },
            },
            "securitySchemes": {
                "OAuth2PasswordBearer": {
                    "type": "oauth2",
                    "flows": {"password": {"scopes": {}, "tokenUrl": "token"}},
                }
            },
        },

                    },
                },
                "securitySchemes": {
                    "OAuth2PasswordBearer": {
                        "type": "oauth2",
                        "flows": {
                            "password": {
                                "scopes": {
                                    "me": "Read information about the current user.",

                    },
                },
            },
            "securitySchemes": {
                "OAuth2PasswordBearer": {
                    "type": "oauth2",
                    "flows": {
                        "password": {
                            "scopes": {},
                            "tokenUrl": "token",
                        }
                    },
                }

    authorizationCode: Optional[OAuthFlowAuthorizationCode] = None


class OAuth2(SecurityBase):
    type_: SecuritySchemeType = Field(default=SecuritySchemeType.oauth2, alias="type")
    flows: OAuthFlows


class OpenIdConnect(SecurityBase):
    type_: SecuritySchemeType = Field(
        default=SecuritySchemeType.openIdConnect, alias="type"
    )
    openIdConnectUrl: str

The sequence of execution before FastAPI 0.106.0 was like this diagram:

Time flows from top to bottom. And each column is one of the parts interacting or executing code.

```mermaid
sequenceDiagram

participant client as Client
participant handler as Exception handler