Config error: both host and hostaddr are missing

[jayvdb]

According to https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-PARAMKEYWORDS

The default behavior when host is not specified, or is empty, is to connect to a Unix-domain socket in /tmp (or whatever socket directory was specified when PostgreSQL was built). On Windows, the default is to connect to localhost.

However tokio-posgres connect prevents host & hostaddr being omitted:

https://github.com/sfackler/rust-postgres/blob/02463b1/tokio-postgres/src/connect.rs#L20-L22

[sfackler]

Correct, the client does not implement that since it doesn't know what socket directory was specified when PostgreSQL was built.

[jayvdb]

On non-Windows, the pg client default is /tmp/.s.PGSQL.5432, however as you indicate it can be changed at the time the client is built.

On Windows, the default if it missing is host=localhost.

Can appreciate you may not want to support this.
I see on https://docs.rs/tokio-postgres/latest/tokio_postgres/config/struct.Config.html it says regarding host

Required if connecting with the connect method.

Perhaps that should be revised to say something like

Either host or hostaddr is required if connecting with the connect method.

And perhaps move that up to the top, so it is more prominent.

Interestingly under "Url" it says

All components are optional

How then does this client connect if all components of the Url are missing?