MDEV-19487: JSON_TYPE doesnt detect the type of String Values

(returns NULL) and for Date/DateTime returns "INTEGER"

Analysis:
When the first character of json is scanned it is number. Based on that
integer is returned.
Fix:
Scan rest of the json before returning the final result to ensure json is
valid in the first place in order to have a valid type.

mysql-test/main/func_json.result

@@ -1697,5 +1697,13 @@ INSERT INTO t (doc) VALUES ('{ "_id" : { "$oid" : "0ca0b0f0" },"a" : [ { "a" : [
 ERROR 22001: Data too long for column 'id' at row 1
 DROP TABLE t;
 #
+# MDEV-19487: JSON_TYPE doesnt detect the type of String Values (returns NULL) and for Date/DateTime returns "INTEGER"
+#
+SELECT JSON_TYPE(json_value(JSON_OBJECT("id", 1, "name", 'Monty', "date", Cast('2019-01-01' as Date) ), '$.date'));
+JSON_TYPE(json_value(JSON_OBJECT("id", 1, "name", 'Monty', "date", Cast('2019-01-01' as Date) ), '$.date'))
+NULL
+Warnings:
+Warning	4038	Syntax error in JSON text in argument 1 to function 'json_type' at position 5
+#
 # End of 10.5 tests
 #

mysql-test/main/func_json.test

@@ -1125,6 +1125,13 @@ INSERT INTO t (doc) VALUES ('{ "_id" : { "$oid" : "0ca0b0f0" },"a" : [ { "a" : [
 
 DROP TABLE t;
 
+--echo #
+--echo # MDEV-19487: JSON_TYPE doesnt detect the type of String Values (returns NULL) and for Date/DateTime returns "INTEGER"
+--echo #
+
+SELECT JSON_TYPE(json_value(JSON_OBJECT("id", 1, "name", 'Monty', "date", Cast('2019-01-01' as Date) ), '$.date'));
+
+
 --echo #
 --echo # End of 10.5 tests
 --echo #

sql/item_jsonfunc.cc

@@ -2971,6 +2971,12 @@ String *Item_func_json_type::val_str(String *str)
     break;
   }
 
+  /* ensure the json is at least valid. */
+  while(json_scan_next(&je) == 0) {}
+
+  if (je.s.error)
+    goto error;
+
   str->set(type, strlen(type), &my_charset_utf8mb3_general_ci);
   return str;