Multi-row REPLACE incorrectly reports duplicate primary key after an auto-generated row

mariadb < case.sql

CREATE DATABASE replace_test;

USE replace_test;

CREATE TABLE combined (id INT AUTO_INCREMENT PRIMARY KEY, u INT UNIQUE) ENGINE=InnoDB;

CREATE TABLE split LIKE combined;

INSERT INTO combined VALUES (1,10),(2,20);

INSERT INTO split VALUES (1,10),(2,20);

DELIMITER //

CREATE PROCEDURE run_case()

BEGIN

  DECLARE CONTINUE HANDLER FOR SQLEXCEPTION

    GET DIAGNOSTICS CONDITION 1 @err_no=MYSQL_ERRNO, @err_msg=MESSAGE_TEXT;

  SET @err_no=0, @err_msg='';

  REPLACE INTO combined VALUES (NULL,10),(2,30);

END//

DELIMITER ;

CALL run_case();

SELECT 'combined_error' AS label, @err_no AS errno, @err_msg AS message;

REPLACE INTO split VALUES (NULL,10);

REPLACE INTO split VALUES (2,30);

SELECT 'combined_rows' AS label,

       GROUP_CONCAT(CONCAT(id,':',u) ORDER BY id) AS rows_value

  FROM combined;

SELECT 'split_rows' AS label,

       GROUP_CONCAT(CONCAT(id,':',u) ORDER BY id) AS rows_value

  FROM split;

SELECT 'oracle' AS label, @err_no=0 AND

  (SELECT GROUP_CONCAT(CONCAT(id,':',u) ORDER BY id) FROM combined)='2:30,3:10'

  AND (SELECT GROUP_CONCAT(CONCAT(id,':',u) ORDER BY id) FROM split)='2:30,3:10' AS passed;

DROP DATABASE replace_test;

SELECT 'cleanup' AS label, COUNT(*)=0 AS passed

  FROM information_schema.schemata WHERE schema_name='replace_test';

combined_error  1062  Duplicate entry '2' for key 'PRIMARY'

combined_rows   1:10,2:20

split_rows      2:30,3:10

oracle          0

cleanup         1