[GENERAL] How to stop array_to_json from interpolating column names that weren't there

[Guyren Howe]

9.6

I’ve a view that shows information about schemas:

 SELECT schemata.catalog_name,
    schemata.schema_name,
    ('/'::text || (schemata.schema_name)::text) AS schema_name_address
   FROM information_schema.schemata
  ORDER BY schemata.catalog_name, schemata.schema_name

Fine. I now want to turn that result set into a JSON array. I can do this:

                SELECT
                        ARRAY_AGG(foo) AS foos
                FROM (
                        SELECT
                                row_to_json(schemata_)
                        FROM
                                schemata_)
                        AS
                                foo
and I get this:

{“(\”{\"\"catalog_name\"\":\"\"ds2_development\"\",\"\"schema_name\"\":\"\"admin\"\",\"\"schema_name_address\"\":\"\"/admin\"\"}\")","(\"
…

which is great. I have an array of perfect JSON objects. Now I just need to 
turn that into a single JSON object. But when I do the obvious:

SELECT array_to_json(
                SELECT
                        ARRAY_AGG(foo) AS foos
                FROM (
                        SELECT
                                row_to_json(schemata_)
                        FROM
                                schemata_)
                        AS
                                foo
)

I get a syntax error. And when I do:

SELECT TO_JSON(foos) FROM (
                SELECT
                        ARRAY_AGG(foo) AS foos
                FROM (
                        SELECT
                                row_to_json(schemata_)
                        FROM
                                schemata_)
                        AS
                                foo
) AS bar

Postgres tries to be helpful by interpolating a column name I don’t want (here, 
row_to_json):

[{“row_to_json":{"catalog_name":"ds2_development","schema_name":"admin","schema_name_address":"/admin"}},{"row_to_json":{"catalog_name":"ds2_development","schema_name":"anon","schema_name_address":"/anon"}},{"row_to_json":
…

I could fix this in PLV8 a tad inefficiently, but I feel like I ought to be 
able to do this in pure SQL and there’s some heuristic or Yet Another Weird 
Corner Case I’m as yet unaware of.

So: can I do this in SQL? How?