sql shell lexical error: unterminated string

[annrpom]

Describe the problem

The cloud sql shell produces an error when a function is defined using the $$ syntax.

To Reproduce

Following some examples from our docs, we observe that the following function:

CREATE OR REPLACE FUNCTION update_code(
  code_name VARCHAR,
  new_rules JSONB
  ) 
  RETURNS promo_codes AS $$
    UPDATE promo_codes SET rules = new_rules
    WHERE code = code_name
    RETURNING *;
  $$ LANGUAGE SQL;

On 23.2.1 using cockroach demo works as expected:

On 23.2.1 using the cloud sql shell produces a lexical error:

This is a bug reported on our community forum by a user when they tried testing out creating a function using a loop:

CREATE FUNCTION fib(n int) RETURNS INT AS $$
    DECLARE
        tmp INT;
        a INT := 0;
        b INT := 1;
        i INT := 2;
    BEGIN
        IF n < 0 THEN
            RAISE EXCEPTION 'n must be non-negative';
        END IF;
        IF n = 0 THEN RETURN 0; END IF;
        IF n = 1 THEN RETURN 1; END IF;
        LOOP
            IF i > n THEN EXIT; END IF;
            tmp := a + b;
            a := b;
            b := tmp;
            i := i + 1;
        END LOOP;
        RETURN b;
    END
  $$ LANGUAGE PLpgSQL;

Jira issue: CRDB-36454

[annrpom]

cc: @lassenordahl