fix: add warning for not specifying charset when using JSON

lib/parsers/text_parser.js

@@ -86,6 +86,13 @@ function compile(fields, options, config) {
       table: field.table,
       name: field.name,
       string: function(encoding = field.encoding) {
+        if (field.columnType === Types.JSON && encoding === field.encoding) {
+          // JSON columns are always returned as BINARY, so we have to
+          // handle them according to JSON specs and use "utf8",
+          // see https://github.com/sidorares/node-mysql2/issues/1661
+          console.warn(`typeCast: JSON column "${field.name}" is interpreted as BINARY by default, recommended to manually set utf8 encoding: \`field.string("utf8")\``);
+        }
+
         return _this.packet.readLengthCodedString(encoding);
       },
       buffer: function() {