JSONB_AGG: aggregate function calls cannot be nested

[Alexander Farber]

Good evening,

I have the following query in 13.2:

# SELECT
                TO_CHAR(finished, 'YYYY-MM-DD') AS day,
                SUM(CASE WHEN reason='regular' or reason='resigned' THEN 1
ELSE 0 END)::int AS completed,
                SUM(CASE WHEN reason='expired' THEN 1 ELSE 0 END)::int AS
expired
        FROM words_games
        WHERE finished > CURRENT_TIMESTAMP - INTERVAL '2 week'
        GROUP BY day
        ORDER BY day;
    day     | completed | expired
------------+-----------+---------
 2021-02-06 |       167 |      71
 2021-02-07 |       821 |     189
 2021-02-08 |       816 |     323
 2021-02-09 |       770 |     263
 2021-02-10 |       864 |     230
 2021-02-11 |       792 |     184
 2021-02-12 |       838 |     231
 2021-02-13 |       853 |     293
 2021-02-14 |       843 |     231
 2021-02-15 |       767 |     203
 2021-02-16 |       744 |     237
 2021-02-17 |       837 |     206
 2021-02-18 |       751 |     196
 2021-02-19 |       745 |     257
 2021-02-20 |       654 |     135
(15 rows)

It works well, but I would like to transform it into a JSONB map with 3
arrays.

So I am trying:

# SELECT
                JSONB_AGG(TO_CHAR(finished, 'YYYY-MM-DD')) AS day,
                JSONB_AGG(SUM(CASE WHEN reason='regular' or
reason='resigned' THEN 1 ELSE 0 END)::int) AS completed,
                JSONB_AGG(SUM(CASE WHEN reason='expired' THEN 1 ELSE 0
END)::int) AS expired
        FROM words_games
        WHERE finished > CURRENT_TIMESTAMP - INTERVAL '2 week'
        GROUP BY day
        ORDER BY day;
ERROR:  aggregate function calls cannot be nested
LINE 3:                 JSONB_AGG(SUM(CASE WHEN reason='regular' or ...
                                  ^

Shouldn't I use JSONB_AGG here, to build the 3 JSON arrays?

Or is the syntax error about being able to use JSONB_AGG only once per
SELECT query?

Greetings
Alex