Using array_agg with filter

[ctron]

I am struggling to use Postgres' array_agg with the FILTER aggregate keyword (see https://www.postgresql.org/docs/current/sql-expressions.html#SYNTAX-AGGREGATES>)

The syntax is like this (but can be used with aggregates in general):

select
  array_agg(something) filter (where foo=bar)
from
 …

I can map the array_agg using a custom Iden:

pub struct ArrayAgg;

impl Iden for ArrayAgg {
    #[allow(clippy::unwrap_used)]
    fn unquoted(&self, s: &mut dyn Write) {
        s.write_str("array_agg").unwrap();
    }
}

Using it as:

.select_column_as(
    SimpleExpr::from(
        Func::cust(ArrayAgg).arg(
            Func::cust(JsonBuildObject)
                .arg("foo1")
                .arg(foo::Column::Col1.into_expr())
                .arg("foo2")
                .arg(foo::Column::Col2.into_expr())
        ),
    ),
    "purls",
)

However, I am struggling to add the filter (where …) part.