A parser for BNF and EBNF grammars used by jison.
npm install ebnf-parser
To build the parser yourself, clone the git repo then run:
make
This will generate parser.js, which is required by ebnf-parser.js.
The parser translates a string grammar or JSON grammar into a JSON grammar that jison can use (ENBF is transformed into BNF).
var ebnfParser = require('ebnf-parser');
// parse a bnf or ebnf string grammar
ebnfParser.parse("%start ... %");
// transform an ebnf JSON gramamr
ebnfParser.transform({"ebnf": ...});
The parser can parse its own BNF grammar, shown below:
%start spec
/* grammar for parsing jison grammar files */
%{
var transform = require('./ebnf-transform').transform;
var ebnf = false;
%}
%%
spec
: declaration_list '%%' grammar optional_end_block EOF
{
$$ = $declaration_list;
if ($optional_end_block && $optional_end_block.trim() !== '') {
yy.addDeclaration($$, { include: $optional_end_block });
}
return extend($$, $grammar);
}
;
optional_end_block
:
| '%%' extra_parser_module_code
{ $$ = $extra_parser_module_code; }
;
optional_action_header_block
:
{ $$ = {}; }
| optional_action_header_block ACTION
{
$$ = $optional_action_header_block;
yy.addDeclaration($$, { actionInclude: $ACTION });
}
| optional_action_header_block include_macro_code
{
$$ = $optional_action_header_block;
yy.addDeclaration($$, { actionInclude: $include_macro_code });
}
;
declaration_list
: declaration_list declaration
{ $$ = $declaration_list; yy.addDeclaration($$, $declaration); }
|
{ $$ = {}; }
;
declaration
: START id
{ $$ = {start: $id}; }
| LEX_BLOCK
{ $$ = {lex: $LEX_BLOCK}; }
| operator
{ $$ = {operator: $operator}; }
| TOKEN full_token_definitions
{ $$ = {token_list: $full_token_definitions}; }
| ACTION
{ $$ = {include: $ACTION}; }
| include_macro_code
{ $$ = {include: $include_macro_code}; }
| parse_param
{ $$ = {parseParam: $parse_param}; }
| parser_type
{ $$ = {parserType: $parser_type}; }
| options
{ $$ = {options: $options}; }
;
options
: OPTIONS token_list
{ $$ = $token_list; }
;
parse_param
: PARSE_PARAM token_list
{ $$ = $token_list; }
;
parser_type
: PARSER_TYPE symbol
{ $$ = $symbol; }
;
operator
: associativity token_list
{ $$ = [$associativity]; $$.push.apply($$, $token_list); }
;
associativity
: LEFT
{ $$ = 'left'; }
| RIGHT
{ $$ = 'right'; }
| NONASSOC
{ $$ = 'nonassoc'; }
;
token_list
: token_list symbol
{ $$ = $token_list; $$.push($symbol); }
| symbol
{ $$ = [$symbol]; }
;
full_token_definitions
: full_token_definitions full_token_definition
{ $$ = $full_token_definitions; $$.push($full_token_definition); }
| full_token_definition
{ $$ = [$full_token_definition]; }
;
// As per http://www.gnu.org/software/bison/manual/html_node/Token-Decl.html
full_token_definition
: optional_token_type id optional_token_value optional_token_description
{
$$ = {id: $id};
if ($optional_token_type) {
$$.type = $optional_token_type;
}
if ($optional_token_value) {
$$.value = $optional_token_value;
}
if ($optional_token_description) {
$$.description = $optional_token_description;
}
}
;
optional_token_type
: /* epsilon */
{ $$ = false; }
| TOKEN_TYPE
;
optional_token_value
: /* epsilon */
{ $$ = false; }
| INTEGER
;
optional_token_description
: /* epsilon */
{ $$ = false; }
| STRING
;
id_list
: id_list id
{ $$ = $id_list; $$.push($id); }
| id
{ $$ = [$id]; }
;
token_id
: TOKEN_TYPE id
{ $$ = $id; }
| id
{ $$ = $id; }
;
grammar
: optional_action_header_block production_list
{
$$ = $optional_action_header_block;
$$.grammar = $production_list;
}
;
production_list
: production_list production
{
$$ = $production_list;
if ($production[0] in $$) {
$$[$production[0]] = $$[$production[0]].concat($production[1]);
} else {
$$[$production[0]] = $production[1];
}
}
| production
{ $$ = {}; $$[$production[0]] = $production[1]; }
;
production
: id ':' handle_list ';'
{$$ = [$id, $handle_list];}
;
handle_list
: handle_list '|' handle_action
{
$$ = $handle_list;
$$.push($handle_action);
}
| handle_action
{
$$ = [$handle_action];
}
;
handle_action
: handle prec action
{
$$ = [($handle.length ? $handle.join(' ') : '')];
if ($action) {
$$.push($action);
}
if ($prec) {
$$.push($prec);
}
if ($$.length === 1) {
$$ = $$[0];
}
}
;
handle
: handle expression_suffix
{
$$ = $handle;
$$.push($expression_suffix);
}
|
{
$$ = [];
}
;
handle_sublist
: handle_sublist '|' handle
{
$$ = $handle_sublist;
$$.push($handle.join(' '));
}
| handle
{
$$ = [$handle.join(' ')];
}
;
expression_suffix
: expression suffix ALIAS
{
$$ = $expression + $suffix + "[" + $ALIAS + "]";
}
| expression suffix
{
$$ = $expression + $suffix;
}
;
expression
: ID
{
$$ = $ID;
}
| STRING
{
$$ = ebnf ? "'" + $STRING + "'" : $STRING;
}
| '(' handle_sublist ')'
{
$$ = '(' + $handle_sublist.join(' | ') + ')';
}
;
suffix
: /* epsilon */
{ $$ = ''; }
| '*'
| '?'
| '+'
;
prec
: PREC symbol
{
$$ = { prec: $symbol };
}
|
{
$$ = null;
}
;
symbol
: id
{ $$ = $id; }
| STRING
{ $$ = $STRING; }
;
id
: ID
{ $$ = $ID; }
;
action
: '{' action_body '}'
{ $$ = $action_body; }
| ACTION
{ $$ = $ACTION; }
| include_macro_code
{ $$ = $include_macro_code; }
| ARROW_ACTION
{ $$ = '$$ =' + $ARROW_ACTION + ';'; }
|
{ $$ = ''; }
;
action_body
:
{ $$ = ''; }
| action_comments_body
{ $$ = $action_comments_body; }
| action_body '{' action_body '}' action_comments_body
{ $$ = $1 + $2 + $3 + $4 + $5; }
| action_body '{' action_body '}'
{ $$ = $1 + $2 + $3 + $4; }
;
action_comments_body
: ACTION_BODY
{ $$ = $ACTION_BODY; }
| action_comments_body ACTION_BODY
{ $$ = $action_comments_body + $ACTION_BODY; }
;
extra_parser_module_code
: optional_module_code_chunk
{ $$ = $optional_module_code_chunk; }
| optional_module_code_chunk include_macro_code extra_parser_module_code
{ $$ = $optional_module_code_chunk + $include_macro_code + $extra_parser_module_code; }
;
include_macro_code
: INCLUDE PATH
{
var fs = require('fs');
var fileContent = fs.readFileSync($PATH, { encoding: 'utf-8' });
// And no, we don't support nested '%include':
$$ = '\n// Included by Jison: ' + $PATH + ':\n\n' + fileContent + '\n\n// End Of Include by Jison: ' + $PATH + '\n\n';
}
| INCLUDE error
{
console.error("%include MUST be followed by a valid file path");
}
;
module_code_chunk
: CODE
{ $$ = $CODE; }
| module_code_chunk CODE
{ $$ = $module_code_chunk + $CODE; }
;
optional_module_code_chunk
: module_code_chunk
{ $$ = $module_code_chunk; }
| /* nil */
{ $$ = ''; }
;
%%
// transform ebnf to bnf if necessary
function extend(json, grammar) {
json.bnf = ebnf ? transform(grammar.grammar) : grammar.grammar;
if (grammar.actionInclude) {
json.actionInclude = grammar.actionInclude;
}
return json;
}
MIT