Postgres trigger side-effect is occurring out of order with row-level security select policy

*Context*
I am using row-level security along with triggers to implement a pure SQL
RBAC implementation. While doing so I encountered a weird behavior between
INSERT triggers and SELECT row-level security policies.

*Question*
I have posted a very detailed question on StackOverflow here:
https://stackoverflow.com/questions/52565720/postgres-trigger-side-effect-is-occurring-out-of-order-with-row-level-security-s

For anyone who is just looking for a summary/repro, I am seeing the
following behavior:

CREATE TABLE a (id TEXT);
ALTER TABLE a ENABLE ROW LEVEL SECURITY;
ALTER TABLE a FORCE ROW LEVEL SECURITY;

CREATE TABLE b (id TEXT);

CREATE POLICY ON a FOR SELECT
USING (EXISTS(
select * from b where a.id = b.id
));

CREATE POLICY ON a FOR INSERT
WITH CHECK (true);

CREATE FUNCTION reproHandler() RETURNS TRIGGER AS $$
BEGIN
RAISE NOTICE USING MESSAGE = 'inside trigger handler';
INSERT INTO b (id) VALUES (NEW.id);
RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER reproTrigger BEFORE INSERT ON a
FOR EACH ROW EXECUTE PROCEDURE reproHandler();

INSERT INTO a VALUES ('fails') returning id;
NOTICE: inside trigger handler
ERROR: new row violates row-level security policy for table "a"

Rather than the error, I expect that something along these lines should
occur instead:

1. A new row ('fails') is staged for INSERT
2. The BEFORE trigger fires with NEW set to the new row
3. The row ('fails') is inserted into b and returned from the trigger
procedure unchanged
4. The INSERT's WITH CHECK policy true is evaluated to true
5. The SELECT's USING policy select * from b where a.id = b.id is
evaluated. *This should return true due to step 3*
6. Having passed all policies, the row ('fails') is inserted in table
7. The id (fails) of the inserted row is returned

If anyone can point me in the right direction I would be extremely thankful.

Carl Sverre

http://www.carlsverre.com