The Custom Languages feature is a great tool to deal with new, not-yet-supported languages. However, I could not find a method to modify existing language plugins.
I develop in Python with a language extension (XHPy, https://github.com/candu/xhpy).
It is a niche software, so I don't expect JetBrains to support it, but I would be happy to write a plugin for this.
All existing python code is valid, but extra syntax is supported:
variable = 'hello world'
* Is it possible to extend the existing python language lexer and parser to add support to this language?
* Is the source code available for python lexer / parser / plugin, so that I can build on top of that?