The Lexer and Parser both expose a collection of Errors. http://sap.github.io/chevrotain/documentation/0_5_19/classes...
http://sap.github.io/chevrotain/documentation/0_5_19/interfa...
Both contain information regarding the position of the error. For a lexer Error it is an offset. For a Parsing Error the erroneous Token is referenced, It contains line/column/offset and more...
If you want to build an Editor using codeMirror you will have to extract that error position information and highlight it using codeMirror's APIs.
example: https://github.com/SAP/chevrotain/blob/gh-pages/playground/e...
Chevrotain is not aware of codeMirror/ACE or any other Editor frameworks. It is just a ±3,000 LOC library meant for building parsers.
If you are indeed interested in building an Online Editor for some language, you may want to have a look here: https://github.com/SAP/demos_json_editor_services_chevrotain
It is a work in progress on using Chevrotain to build Editor services (outline/formatting/Ast Building/...).