Customizable Error Messages

Chevrotain allows users to customize both the parser and lexer error messages. This can be accomplished by implementing the following interfaces:

• IParserErrorMessageProvider
• ILexerErrorMessageProvider

See executable examples:

• Custom Parser Errors.
• Custom Lexer Errors.

In addition it is also possible to directly provide strings values to be used in errors for specific parsing DSL methods, for example:

$.RULE("myStatement", () => {
  // ...
  $.CONSUME(SemiColon, {
    ERR_MSG: "expecting semiColon at end of myStatement",
  });
});

The ERR_MSG config property is available for the following DSL methods:

• CONSUME
• OR
• AT_LEAST_ONE
• AT_LEAST_ONE_SEP