Array serialization does not work with custom array types

Consider the following schema:

CREATE TABLE my_table (my_array text[]);

If you run:

sql.unsafe(`insert into my_table (my_array) values ($1)`, [['item']]);

...it works as expected.

Now instead of using a built-in type, change the array to be a custom array type:

CREATE DOMAIN my_custom_array_type AS text[]; 
CREATE TABLE my_table (my_array my_custom_array_type);

Running the same code:

sql.unsafe(`insert into my_table (my_array) values ($1)`, [['item']]);

...now fails with the following error:

Uncaught PostgresError: malformed array literal: "item"

There appears to be an issue with serializing arrays, but only for custom array types.

Why would you want to use such custom types? One possible reason is if you want to constrain the length of the array, e.g.

CREATE DOMAIN my_custom_array_type AS text[] 
  CONSTRAINT my_custom_array_type_check CHECK ((array_length(VALUE, 1) <= 3)) // At most 3 elements

It appears to have something to do with how we're defining the serializers for these custom types:
https://github.com/porsager/postgres/blob/364c3ebee57f3a7ce1fc36d5857b574ee72e507c/src/connection.js#L725-L736

Start with src/connection.js lines 725-736 and reproduce the issue using the shown PostgreSQL schema and sql.unsafe call. Trace how serializers are selected for the custom array domain, then verify that inserting a JavaScript array works for both the built-in text[] type and the custom type.