application_name doesn't seem accepted

• asyncpg version: 0.23.0
• PostgreSQL version: 12.3
• **Do you use a PostgreSQL SaaS? **: false
• Python version: 3.9
• Platform:
• Do you use pgbouncer?: false
• Did you install asyncpg with pip?: true
• If you built asyncpg locally, which version of Cython did you use?:
• Can the issue be reproduced under both asyncio and uvloop?:

taking some code written by zzzeek himself https://stackoverflow.com/a/15691283:

create_async_engine(f"postgresql+asyncpg://{user}:{password}@{hostname}/{database_name}?application_name={APPNAME}")

yields

E           TypeError: connect() got an unexpected keyword argument 'application_name'

using instead something I found in an issue here https://github.com/MagicStack/asyncpg/issues/204

    create_async_engine(
        f"postgresql+asyncpg://{user}:{password}@{hostname}/{database_name}",
        server_settings={"application_name": APPNAME},
    )

yields instead

E           TypeError: Invalid argument(s) 'server_settings' sent to create_engine(), using configuration PGDialect_asyncpg/AsyncAdaptedQueuePool/Engine.  Please check that the keyword arguments are appropriate for this combination of components.

[elprans]

That said,

    create_async_engine(
        f"postgresql+asyncpg://{user}:{password}@{hostname}/{database_name}",
        connect_args={"server_settings": {"application_name": APPNAME}},
    )

should work

[elprans]

It’s asyncpg which rejects the application_name parameter

The application_name, like other server-side options should be passed in the server_settings dictionary argument to connect().

In your case, SQLAlchemy is incorrectly interpreting the DSN and tries to pass application_name directly to connect(), and in the explicit argument scenario you should pass it like I’ve shown above.