Format Quick-start Guide

Formatter definition

Create a MyDsl.format file in the core plugin of the language in the <dsl-name>.formatting package - e.g. org.xtext.example.mydsl.formatting.

Base class

The default base class for AbstractXXXFormatter is AbstractDdkFormatter - if any other has to be specified then the extends clause has to be defined in the format configuration file (.format), just after the grammar and optional extended formatter names, together with this custom base formatter class qualified name - see below - 2nd line:

    formatter for org.xtext.example.mydsl.MyDsl with org.eclipse.xtext.common.Terminals
    extends com.avaloq.tools.foundation.xtext.core.formatting.AbstractCustomFormatter

    //constants, rules, etc. 2

Formatter custom code

Ensure that MyDslFormatter extends AbstractMyDslFormatter generated out of Format DSL.

Project configuration

Ensure that your language core plugin has a Xtext nature

Example

MyDsl Xtext grammar on which a basic and a complex Format examples are based.

grammar org.xtext.example.mydsl.MyDsl with org.eclipse.xtext.common.Terminals

generate myDsl "http://www.xtext.org/example/mydsl/MyDsl"

MyDsl :
  "begin"
  (elements+=Element)*
  "end";

Element :
  "element" name=ID
  (
    ("min" "=" min=SignedInt)
    | ("max" "=" max=SignedInt)
  );

SignedInt :
  ("+" | "-")? INT;

Basic example

formatter for org.xtext.example.mydsl.MyDsl

MyDsl {
  "begin" : increment after, linewrap after;
  "end" : decrement before, linewrap before;
}

Complex example

formatter for org.xtext.example.mydsl.MyDsl

const int FOO = 2;

MyDsl {
  "begin" : increment after, linewrap FOO after;
  "end" : decrement before, linewrap before;
}

Element {
  rule : linewrap before; // (1)
  group 1 => group 1 { // (2)
    "=" : space " " around; // (3)
    "min" : linewrap before, column 10 before;
  }
  group 1 => group 2 : linewrap before; // (4)
  "="(2,2) : space " " around; // (5)
  =max, =min : offset 20 before; // (6)
  SignedInt, "max" : no_linewrap between; // (7)
}

* {
  ["=", "."] : no_space before; // (8)
  ("begin" "end") : left.linewrap after, right.linewrap before; // (9)
}

An explanation to the Element declarations in the above example:

1. rule

   specifies the grammar rule Element, i.e. line-wrap before each Element

2. group 1 => group 1 ...

   specifies that the context is the min alternative

3. "="

   this is used in the nested group context and refers to the 1st equals sign i.e. the "=" following keyword "min"

4. group 1 => group 2 : ...

   specifies the compound element containing the max assignment

5. "="(2,2)

   this references equals sign 2 of 2 in Element, i.e. the "=" following keyword "max"

6. =max, =min

   formatting applies to min and max assignments

7. SignedInt, "max"

   suppress line wrapping bewteen rule SignedInt and keyword “max”

8. ["=", "."]

   All "=" and "." keywords in the Grammar. In contrast to declaration in 3. this does not refer to a specific keyword, but all keywords with values "=" or ".".

9. ("begin" "end")

   Find all keyword pairs begin and end in the Grammar and configure a linewrap after begin and a linewrap before end.