Describing a language editor can be repetitive, for instance when you have to define expressions. expression '+' expression and expression '*' expression is a typical example. From the grammar file that describes the language structure it's possible to recognize repetitive rule structures and build an editor in a consistent way.

The PE project defines a grammar and generates AST in a way not related to any projectional editor. PE4MPS project imports the generated ASTs into MPS generating for example from this rule:

Graph:
      strict=STRICT? type=GraphType name=string?
      statementList<indentList('{', '}')>=Statement*
    ;
    

this MPS editor:

There are several strategies for code generation. The one used by MPS could be called no code generation strategy. In fact the suggested implementation for code generation is first to transform models in your language to models in the target language, or if you prefer first to transform AST representation of your program into AST representation of target language. Then models from a real language, for example Java, are translated to text. This means that only construct, like if-then-else, of language that one can compile or execute, like Java, have a place where one say how to translate them to text, in MPS called TextGen aspect.

MPS gives you for free a language called baseLanguge that transform seamlessly to Java. Whereas one of my target languages is Javascript, so I created this new MPS language. The new project is hosted on github.