further work on zaach#363 fixing the ARROW_ACTION action by placing the received user-defined action code within () braces so that the generated parser will certainly treat the entire blurb as a single JavaScript *expression* rather than a single or compound *statement*; also note commit SHA-1: 1c8c89d :: BNF parser: produce stricter action code for arrow action in any jison grammar so that we can more easily check coding mistakes in a production's arrow code, e.g. unwanted semicolons, multiple statements, etc., which can currently slip through the net and cause hard-to-diagnose havoc down the line.

Adjusted unit tests accordingly.

Author: GerHobbelt

examples/parser-to-lexer-communication-test-w-debug.jison

@@ -44,54 +44,54 @@
 
 
 S
-    : init x x e                -> parser.trace('S:complete = ', $e);
+    : init x x e                { parser.trace('S:complete = ', $e); }
     ;
 
 init
-    : %epsilon                  -> parser.trace('init:epsilon');
+    : %epsilon                  { parser.trace('init:epsilon'); }
     ;
 
 x
-    : %epsilon                  -> parser.trace('X:epsilon');                    $$ = '<X-epsilon>';
+    : %epsilon                  { parser.trace('X:epsilon');                    $$ = '<X-epsilon>'; }
     ;
 
 e
-    : cmd e                     -> parser.trace('e:cmd=', $cmd);                 $$ = $cmd + ' | ' + $e;
-    | %epsilon                  -> parser.trace('e:epsilon');                    $$ = '<E-epsilon>';
+    : cmd e                     { parser.trace('e:cmd=', $cmd);                 $$ = $cmd + ' | ' + $e; }
+    | %epsilon                  { parser.trace('e:epsilon');                    $$ = '<E-epsilon>'; }
     ;
 
 cmd
-    : a                         -> parser.trace('cmd:a');                        $$ = $a;
-    | f_a                       -> parser.trace('cmd:function a()');             $$ = $f_a;
-    | b                         -> parser.trace('cmd:b');                        $$ = $b;
-    | f_b                       -> parser.trace('cmd:function b()');             $$ = $f_b;
-    | error                     -> parser.trace('cmd:error', get_reduced_error_info_obj($error) || $error);            yyerrok; yyclearin; $$ = 'ERROR';
+    : a                         { parser.trace('cmd:a');                        $$ = $a; }
+    | f_a                       { parser.trace('cmd:function a()');             $$ = $f_a; }
+    | b                         { parser.trace('cmd:b');                        $$ = $b; }
+    | f_b                       { parser.trace('cmd:function b()');             $$ = $f_b; }
+    | error                     { parser.trace('cmd:error', get_reduced_error_info_obj($error) || $error);            yyerrok; yyclearin; $$ = 'ERROR'; }
     ;
 
 a
-    : A                         -> parser.trace('a:A');                          $$ = 'A[' + $A + ']';
+    : A                         { parser.trace('a:A');                          $$ = 'A[' + $A + ']'; }
     ;
 
 f_a
-    : A lb e rb                 -> parser.trace('function a:', $e);              $$ = 'A' + $lb + $e + $rb;
+    : A lb e rb                 { parser.trace('function a:', $e);              $$ = 'A' + $lb + $e + $rb; }
     ;
 
 b
-    : B                         -> parser.trace('b:B');                          $$ = 'B[' + $B + ']';
+    : B                         { parser.trace('b:B');                          $$ = 'B[' + $B + ']'; }
     ;
 
 f_b
-    : B lb e rb                 -> parser.trace('function b:', $e);              $$ = 'B' + $lb + $e + $rb;
+    : B lb e rb                 { parser.trace('function b:', $e);              $$ = 'B' + $lb + $e + $rb; }
     ;
 
 lb
-    : '('                       -> parser.trace('lb+PUSH:[(] ');                 yy.lexer.pushState('alt'); $$ = '(';
-    | BEGIN                     -> parser.trace('lb:[alt-(] ');                  $$ = '{';
+    : '('                       { parser.trace('lb+PUSH:[(] ');                 yy.lexer.pushState('alt'); $$ = '('; }
+    | BEGIN                     { parser.trace('lb:[alt-(] ');                  $$ = '{'; }
     ;
 
 rb
-    : ')'                       -> parser.trace('lb:[)] ');                      $$ = ')';
-    | END                       -> parser.trace('lb+POP:[alt-)] ');              yy.lexer.popState(); $$ = '}';
+    : ')'                       { parser.trace('lb:[)] ');                      $$ = ')'; }
+    | END                       { parser.trace('lb+POP:[alt-)] ');              yy.lexer.popState(); $$ = '}'; }
     ;
 
 %%

packages/ebnf-parser/parser.js

@@ -382,6 +382,7 @@ import XRegExp from '@gerhobbelt/xregexp';       // for helping out the `%option
   import fs from 'fs';
   import transform from './ebnf-transform';
 
+
 // See also:
 // http://stackoverflow.com/questions/1382107/whats-a-good-way-to-extend-error-in-javascript/#35881508
 // but we keep the prototype.constructor and prototype.name assignment lines too for compatibility
@@ -435,6 +436,7 @@ JisonParserError.prototype.name = 'JisonParserError';
 
 
 
+
         // helper: reconstruct the productions[] table
         function bp(s) {
             var rv = [];
@@ -2350,7 +2352,7 @@ case 115:
     // END of default action (generated by JISON mode classic/merge :: 1,VT,VA,VU,-,LT,LA,-,-)
 
 
-    this.$ = '$$ = ' + yyvstack[yysp];
+    this.$ = '$$ = (' + yyvstack[yysp] + ');';
     break;
 
 case 119:

packages/ebnf-parser/tests/bnf_parse.js

@@ -266,7 +266,7 @@ describe("BNF parser", function () {
 
   it("test expression action", function () {
     var grammar = "%% test: foo bar -> $foo\n;";
-    var expected = {bnf: {test: [["foo bar","$$ = $foo"]]}};
+    var expected = {bnf: {test: [["foo bar","$$ = ($foo);"]]}};
 
     assert.deepEqual(bnf.parse(grammar), expected, "grammar should be parsed correctly");
   });

tests/parser/generator.js

@@ -374,7 +374,7 @@ describe("Parser Generator API", function () {
       'expressions\n    : e EOF\n        {return $1;}\n    ;\n\n' +
       'e\n    : phrase+ \'joy\'? -> $1 + \' \' + yytext \n    ;\n\n' +
       'phrase\n    : \'happy\' \'happy\' \'joy\' \'joy\' ' +
-      ' -> [$1, $2, $3, $4].join(\' \'); \n    ;';
+      ' -> [$1, $2, $3, $4].join(\' \') \n    ;';
 
     var parser = new Jison.Parser(grammar);
     var generated = parser.generate();