antlr 重写规则的输出 [英] antlr rewriting output of a rule

问题描述

我正在尝试编写一个 antlr 脚本，其中规则 1 有一个子规则规则 2.我在规则 1 上使用 StringTemplate.

I am trying to write an antlr script where in, rule1 has a subrule , rule2. I am using StringTemplate on rule 1.

我想做的是在规则1消耗/使用之前重组规则2匹配的文本.我该怎么做?

What I want to do, is restructure the text matched by rule2 before it is consumed/used by rule1. How do I do that ?

options{
output=template;
}

rule1 :
  begin sub-rule2 end ';' -> meth(body={rule1.text})

sub-rule2 :
   sub-rule3
 | sub-rule4
 | sub-rule5;

这里的meth"是字符串模板调用

here "meth" is the stringtemplate call

如果说子规则 4 匹配select * from dual;"，我希望将其传递给 rule1#sql (select * from dual);".

If say sub-rule 4 matches "select * from dual;", I would like this to be passed to rule1 "#sql (select * from dual);".

这是我的实际代码，我希望与 select_statement 规则匹配的语句包含在#sql()"中，并在stats"列表中传递给meth"模板的body"属性:

Here is my Actual code I would like the statements matched by the select_statement rule to be wrapped in '#sql()' and to be passed in "stats" list to the "body" attribute of the "meth" template :

body 
@init {
      List stats = new ArrayList();
    }   :   
    BEGIN s=statement{ stats.add($s.text); } SEMI ( s=statement{ stats.add($s.text); } SEMI | pragma SEMI )*
    ( EXCEPTION exception_handler+ )? END ID? -> method(modifiers={"public"},returnType={"void"},name={"execute"},body={stats})
    ;


statement :
    label*
    ( assign_or_call_statement
    | case_statement
    | close_statement
    | continue_statement
    | basic_loop_statement
    | execute_immediate_statement
    | exit_statement
    | fetch_statement
    | for_loop_statement
    | forall_statement
    | goto_statement
    | if_statement
    | null_statement
    | open_statement
    | plsql_block
    | raise_statement
    | return_statement
    | sql_statement 
    | while_loop_statement
    ) 
    ;

    sql_statement
    : (commit_statement
    | delete_statement
    | insert_statement
    | lock_table_statement
    | rollback_statement
    | savepoint_statement
    | select_statement 
    | set_transaction_statement
    | update_statement )
    ;


    select_statement :
        SELECT swallow_to_semi 
    ;

    SELECT  :   'select';

    swallow_to_semi :
        ~( SEMI )+
    ;

推荐答案

您可以像这样具体定义规则可以返回的内容:

You can specifically define what a rule can return like this:

sub_rule2 returns [String x] 
  :  sub_rule3 {$x = ... }
  |  sub_rule4 {$x = "#sql (" + $sub_rule4.text + ");";}
  |  sub_rule5 {$x = ... }
  ;

现在 sub_rule2 返回一个 String x 你可以这样使用:

Now sub_rule2 returns a String x which you can use like this:

rule1
  :  ... sub_rule2 ... -> meth(body={sub_rule2.x})
  ;

注意 sub_rule2.x.

您还可以创建一个自定义方法来检查要添加到 List 的文本是否以 "select " 开头，如下所示:

You could also create a custom method that checks if the text to be added to the List starts with "select " like this:

grammar YourGrammarName;

options{
  output=template;
}

@parser::members {
  private void addStat(String stat, List<String statList>) {
    // 1. if `stat` starts with "select ", wrap "#sql(...)" around it.
    // 2. add `stat` to `statList`
  }
}

body 
@init {
  List<String> stats = new ArrayList<String>();
}   
  :  BEGIN s=statement { addStat($s.text, stats); } SEMI 
     ( s=statement     { addStat($s.text, stats); } SEMI 
     | pragma                                      SEMI
     )*
     (EXCEPTION exception_handler+)? END ID? 

     -> method(modifiers={"public"},returnType={"void"},name={"execute"},body={stats})
  ;

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