Leading comments and client applications

Hi,
I'm trying to understand a behavior where, with our Postgres client, a leading comment in a SQL script causes the CREATE FUNCTION statement following it to be not executed. I can't figure out if this is a bug somewhere or just a misunderstanding on my part. I would appreciate some help understanding.

Here's the contents of foo.sql --

-- this is a comment
CREATE FUNCTION foo(bar text) RETURNS text AS $$
SELECT bar
$$
LANGUAGE sql IMMUTABLE PARALLEL SAFE
;

When I feed that to 'psql -f foo.sql', the function is created as I expect. In the Postgres log, the leading comment *doesn't* appear. I see the same behavior if I just copy/paste the function into psql.

Our test system uses Python 3.8, SQLAlchemy 1.3.6, and psycopg 2.8.5, and when our test harness reads foo.sql and passes it to SQLAlchemy's execute(), I can see in the Postgres log that the leading comment is *not* stripped, and the function isn't created.

The server is Postgres 11.

My naive interpretation is that one of the client layers (SQLAlchemy or psycopg2) should be stripping the leading comment but isn't, but that seems like a lot of responsibility to push onto a client application. I figured that would be the responsibility of the Postgres parser.

I'd be grateful for any insights about what I'm missing.

Thanks
Philip