ERROR when try/catch inside a subtransaction block

[BaiShaoqi]

Expected behavior

NOTICE:  caught
CONTEXT:  PL/Python function "try_catch_inside_subtransaction"
 try_catch_inside_subtransaction
---------------------------------

(1 row)

 i
---
 1
(1 row)

NOTICE:  caught
CONTEXT:  PL/Python function "pk_violation_inside_subtransaction"
 pk_violation_inside_subtransaction
------------------------------------

(1 row)

 i
---
 1
(1 row)

Actual behavior

WARNING:  forcibly aborting a subtransaction that has not been exited
ERROR:  PL/Container client exception occurred:
DETAIL:  Error receiving subtransaction exit error message


 i
---
(0 rows)

WARNING:  forcibly aborting a subtransaction that has not been exited
ERROR:  PL/Container client exception occurred:
DETAIL:  Error receiving subtransaction exit error message

 i
---
(0 rows)

Step to reproduce the behavior

CREATE TABLE subtransaction_tbl (
    i integer
);

CREATE FUNCTION try_catch_inside_subtransaction() RETURNS void
AS $$
# container: plc_python_shared
with plpy.subtransaction():
     plpy.execute("INSERT INTO subtransaction_tbl VALUES (1)")
     try:
         plpy.execute("INSERT INTO subtransaction_tbl VALUES ('a')")
     except plpy.SPIError:
         plpy.notice("caught")
$$ LANGUAGE plcontainer;

SELECT try_catch_inside_subtransaction();
SELECT * FROM subtransaction_tbl;
TRUNCATE subtransaction_tbl;

ALTER TABLE subtransaction_tbl ADD PRIMARY KEY (i);

CREATE FUNCTION pk_violation_inside_subtransaction() RETURNS void
AS $$
# container: plc_python_shared
with plpy.subtransaction():
     plpy.execute("INSERT INTO subtransaction_tbl VALUES (1)")
     try:
         plpy.execute("INSERT INTO subtransaction_tbl VALUES (1)")
     except plpy.SPIError:
         plpy.notice("caught")
$$ LANGUAGE plcontainer;

SELECT pk_violation_inside_subtransaction();
SELECT * FROM subtransaction_tbl;
DROP TABLE subtransaction_tbl;

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[zhangh43]

The RCA of this issue is the result of execution of plpy.execute is not return back to Container through a message, but error out directly.
In fact try except logic in container should be responsible for whether the plpy.execute should error out or not.

try:
    plpy.execute("INSERT INTO subtransaction_tbl VALUES (1)")
except plpy.SPIError:
    plpy.notice("caught")