MDEV-27151: JSON_VALUE() does not parse NULL properties properly

Analysis: JSON_VALUE() returns "null" string instead of NULL pointer.
Fix: When the type is JSON_VALUE_NULL (which is also a scalar) set
null_value to true and return 0 instead of returning string.

2 files changed, 46 insertions, 0 deletions

diff --git a/mysql-test/main/func_json.result b/mysql-test/main/func_json.result
index 8e3b47e322a..2c3cb2f1e72 100644
--- a/mysql-test/main/func_json.result
+++ b/mysql-test/main/func_json.result
@@ -1016,5 +1016,32 @@ j
 {"ID": "4", "Name": "Betty", "Age": 19}
 drop table t1;
 #
+# MDEV-27151: JSON_VALUE() does not parse NULL properties properly
+#
+#
+# It is correct for JSON_EXTRACT() to give null instead of "NULL" because
+# it returns the json literal that is put inside json.
+# Hence it should return null as in 'null' string and not SQL NULL.
+# JSON_VALUE() returns the "VALUE" so it is correct for it to return SQl NULL
+#
+SELECT NULL;
+NULL
+NULL
+SELECT JSON_VALUE('{"nulltest": null}', '$.nulltest');
+JSON_VALUE('{"nulltest": null}', '$.nulltest')
+NULL
+SELECT 1 + NULL;
+1 + NULL
+NULL
+SELECT 1 + JSON_VALUE('{"nulltest": null}', '$.nulltest');
+1 + JSON_VALUE('{"nulltest": null}', '$.nulltest')
+NULL
+SELECT NULL;
+NULL
+NULL
+SELECT JSON_EXTRACT('{"a":null, "b":10, "c":"null"}', '$.a');
+JSON_EXTRACT('{"a":null, "b":10, "c":"null"}', '$.a')
+null
+#
 # End of 10.3 tests
 #
diff --git a/mysql-test/main/func_json.test b/mysql-test/main/func_json.test
index 16f323a9a56..51961c0406a 100644
--- a/mysql-test/main/func_json.test
+++ b/mysql-test/main/func_json.test
@@ -628,5 +628,24 @@ SELECT * FROM t1 WHERE JSON_EXTRACT(j, '$.Age')=19;
 drop table t1;
 
 --echo #
+--echo # MDEV-27151: JSON_VALUE() does not parse NULL properties properly
+--echo #
+--echo #
+--echo # It is correct for JSON_EXTRACT() to give null instead of "NULL" because
+--echo # it returns the json literal that is put inside json.
+--echo # Hence it should return null as in 'null' string and not SQL NULL.
+--echo # JSON_VALUE() returns the "VALUE" so it is correct for it to return SQl NULL
+--echo #
+
+SELECT NULL;
+SELECT JSON_VALUE('{"nulltest": null}', '$.nulltest');
+SELECT 1 + NULL;
+SELECT 1 + JSON_VALUE('{"nulltest": null}', '$.nulltest');
+
+
+SELECT NULL;
+SELECT JSON_EXTRACT('{"a":null, "b":10, "c":"null"}', '$.a');
+
+--echo #
 --echo # End of 10.3 tests
 --echo #