Question

I m modifying a DSL grammar for a product that is in public use. Currently all /*...*/ comments are silently ignored, but I need to modify it so that comments that are placed before certain key elements are parsed into the AST. I need to maintain backwards compatibility whereby users can still add comments arbitrarily throughout the DSL and only those key comments are included.

目前,教区认为:

grammar StateGraph;
graph:  graph  ID  {  graph_body  } ;
graph_body: state+;
state:  state  ID  {  state_body  } ;
state_body: transition* ...etc...; 
transition:  transition  (transition_condition) ID  ; ;
COMMENT:  /*  ( options {greedy=false;} : . )*  */  {skip();}

Comments placed before the graph and state elements contain meaningful description and annotations and need to be included within the parsed AST. So I ve modified those two rules and am no longer skipping COMMENT:

graph: comment*  graph  ID  {  graph_body  } ;
state: comment*  state  ID  {  state_body  } ;
COMMENT:  /*  ( options {greedy=false;} : . )*  */

If I naively use the above, the other comments cause mismatched token errors when subsequently executing the tree parser. How do I ignore all instances of COMMENT that are not placed in front of graph or state ?

一个例子是:

/* Some description
 * @some.meta.info
 */
graph myGraph {
  /* Some description of the state.
   * @some.meta.info about the state
   */
  state first {
    transition if (true) second; /* this comment ignored */
  }

  state second {
  }

  /* this comment ignored */
}

Answer 1

This is the solution I ve actually got working. I d love feedback.

The basic idea is to send comments to the HIDDEN channel, manually extract them in the places where I want them, and to use rewrite rules to re-insert the comments where needed. The extraction step is inspired by the information here: http://www.antlr.org/wiki/pages/viewpage.action?pageId=557063.

图表目前为:

grammar StateGraph;

@tokens { COMMENTS; }

@members {
// matches comments immediately preceding specified token on any channel -> ^(COMMENTS COMMENT*)
CommonTree treeOfCommentsBefore(Token token) {
    List<Token> comments = new ArrayList<Token>();
    for (int i=token.getTokenIndex()-1; i >= 0; i--) {
       Token t = input.get(i);
       if (t.getType() == COMMENT) {
          comments.add(t);
       }
       else if (t.getType() != WS) {
          break;
       }
    }
    java.util.Collections.reverse(comments);

    CommonTree commentsTree = new CommonTree(new CommonToken(COMMENTS, "COMMENTS"));
    for (Token t: comments) {
       commentsTree.addChild(new CommonTree(t));
    }
    return commentsTree;
}
}

graph
    :  graph  ID  {  graph_body  } 
      -> ^(ID {treeOfCommentsBefore($start)} graph_body);
graph_body: state+;
state
    :  state  ID  {  state_body  } 
      -> ^(ID {treeOfCommentsBefore($start)} staty_body);
state_body: transition* ...etc...; 
transition:  transition  (transition_condition) ID  ; ;
COMMENT:  /*  .*  */  {$channel=HIDDEN;}

Answer 2

你们是否做了这项工作?

grammar StateGraph;
graph:  graph  ID  {  graph_body  } ;
graph_body: state+;
state: .COMMENT  state  ID  {  state_body  } ;
state_body: .COMMENT transition* ...etc...; 
transition:  transition  (transition_condition) ID  ; ;
COMMENT:  /*  ( options {greedy=false;} : . )*  */  {skip();}

Answer 3

我如何忽视没有排在图表或国家前面的所有言论?

检查<>后<> 评注的结尾<代码>*/“,>有:graph ,有> 或前面的国家,其中有一些任择空间。如果情况如此,就没有做任何事情,如果情况并非如此,那么,通过<>>/em>获得的排名即告失败。该规则仅限skip()。



在荷兰皇家骑士团,希望:

COMMENT
 :  /*  .*  */  ( (SPACE* (GRAPH | STATE))=> /* do nothing, so keep this token */ 
                | {skip();}                  /* or else, skip it               */ 
                )
 ;

GRAPH  :  graph ;
STATE  :  state ;
SPACES : SPACE+ {skip();};

fragment SPACE :     |  	  |  
  |  
 ;


注:* and .+ are ungreedy byault: no need to set options{greedy=false;}。

并且知道你没有在<条码>上使用。自<代码>SPACES>> 采用<代码>skip() 方法,时称!

友情链接