OptionalactionsAn optional array of actions that can be taken on this diagnostic.
The start position of the relevant text.
OptionalmarkWhen given, add an extra CSS class to parts of the code that this diagnostic applies to.
The message associated with this diagnostic.
OptionalrenderAn optional custom rendering function that displays the message as a DOM node.
The severity of the problem. This will influence how it is displayed.
OptionalsourceAn optional source string indicating where the diagnostic is coming from. You can put the name of your linter here, if applicable.
The end position. May be equal to from, though actually
covering text is preferable.
Describes a problem or hint for a piece of code.