PG Bug reporting form <noreply@postgresql.org> writes:
> given the following simplified table with one row inserted:
>> create table testa ( id serial, test text[] default
> '{"test","test2"}'::text[] );
>> insert into testa values (default);
> when we try to populate a record of testa type we run into trouble with
> postgres in version 9.6.15
>> select jsonb_populate_record(null::testa , to_jsonb(testa)) FROM testa;
> ERROR: 22P02: malformed array literal: "["test", "test2"]"
> DETAIL: "[" must introduce explicitly-specified array dimensions.
> LOCATION: array_in, arrayfuncs.c:269
Yeah, this is something we aren't going to risk changing pre-v10.
cf35346e8 is what fixed it, but that was a pretty massive rewrite
with bugs of its own, and IIRC it changed some other behaviors
that were less obviously bugs than the case you're complaining of.
regards, tom lane