Initial commit. Note that I'm using CommonJS modules and node purely to help me develop this. If this ends up being useful, I will likely distribute the entire package as a single JS file for easier consumption in the browser.

Rakefile

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+file "lib/handlebars/parser.js" => "src/handlebars.yy" do
+  system "jison src/handlebars.yy"
+  sh "mv handlebars.js lib/handlebars/parser.js"
+end
+
+task :default => "lib/handlebars/parser.js"

lib/handlebars.js

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+var ast     = require("handlebars/ast");
+var Lexer   = require("handlebars/handlebars_lexer").Lexer;
+var printer = require("handlebars/printer");
+var parser  = require("handlebars/parser").parser;
+
+parser.yy = {
+  ProgramNode: ast.ProgramNode,
+  MustacheNode: ast.MustacheNode,
+  ContentNode: ast.ContentNode,
+  IdNode: ast.IdNode,
+  StringNode: ast.StringNode,
+  PartialNode: ast.PartialNode,
+  CommentNode: ast.CommentNode,
+  BlockNode: ast.BlockNode,
+  inspect: function(obj) {
+    var sys = require("sys");
+    sys.print(sys.inspect(obj) + "\n");
+  }
+}
+
+parser.lexer = new Lexer;
+
+exports.parse = function(string) {
+  return parser.parse(string);
+};
+
+exports.print = function(ast) {
+  var out = new PrintVisitor().accept(ast);
+  require("sys").print(out);
+}

lib/handlebars/ast.js

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+var ProgramNode = function(statements, inverse) {
+  this.type = "program";
+  this.statements = statements;
+  this.inverse = inverse;
+};
+
+var MustacheNode = function(params) {
+  this.type = "mustache";
+  this.id = params[0];
+  this.params = params.slice(1);
+};
+
+var PartialNode = function(id) {
+  this.type = "partial";
+  this.id = id;
+};
+
+var BlockNode = function(mustache, program) {
+  this.type = "block";
+  this.mustache = mustache;
+  this.program  = program;
+};
+
+var ContentNode = function(string) {
+  this.type = "content";
+  this.string = string;
+}
+
+var IdNode = function(id) {
+  this.type = "ID"
+  this.id = id;
+}
+
+StringNode = function(string) {
+  this.type = "STRING";
+  this.string = string;
+}
+
+CommentNode = function(comment) {
+  this.type = "comment";
+  this.comment = comment;
+}
+
+if(exports) {
+  exports.ProgramNode  = ProgramNode;
+  exports.MustacheNode = MustacheNode;
+  exports.ContentNode  = ContentNode;
+  exports.IdNode       = IdNode;
+  exports.StringNode   = StringNode;
+  exports.PartialNode  = PartialNode;
+  exports.CommentNode  = CommentNode;
+  exports.BlockNode    = BlockNode;
+}

lib/handlebars/handlebars_lexer.js

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+if(require) {
+  var Lexer = require("handlebars/jison_ext").Lexer
+}
+
+var HandlebarsLexer = function() {
+  this.state = "CONTENT";
+};
+HandlebarsLexer.prototype = new Lexer;
+
+HandlebarsLexer.prototype.lex = function() {
+  if(this.input === "") return;
+
+  this.setupLex();
+
+  var lookahead = this.peek(2);
+  var result = '';
+
+  if(this.state == "MUSTACHE") {
+    // chomp optional whitespace
+    while(this.peek() === " ") { this.readchar(); }
+
+    if(this.peek(2) === "}}") {
+      this.state = "CONTENT"
+      this.getchar(2);
+
+      if(this.peek() == "}") this.getchar();
+      return "CLOSE";
+    } else if(this.peek() === '"') {
+      this.getchar();
+      while(this.peek() !== '"') { this.getchar() }
+      this.getchar();
+      return "STRING";
+    } else {
+      while(this.peek().match(/[A-Za-z]/)) { this.getchar() }
+      return "ID"
+    }
+  } else if(lookahead == "{{") {
+    this.state = "MUSTACHE";
+    this.getchar(2);
+
+    var peek = this.peek();
+
+    if(peek === ">") {
+      this.getchar();
+      return "OPEN_PARTIAL";
+    } else if(peek === "#") {
+      this.getchar();
+      return "OPEN_BLOCK";
+    } else if(peek === "/") {
+      this.getchar();
+      return "OPEN_ENDBLOCK";
+    } else if(peek === "^") {
+      this.getchar();
+      return "OPEN_INVERSE"
+    } else if(peek === "!") {
+      this.getchar();
+      this.setupLex();
+      while(this.peek(2) !== "}}") { this.getchar(); };
+      this.readchar(2);
+      this.state = "CONTENT"
+      return "COMMENT";
+    } else {
+      return "OPEN";
+    }
+  } else {
+    while(this.peek(2) !== "{{" && this.peek(2) !== "") { result = result + this.getchar(); }
+    return "CONTENT"
+  }
+};
+
+if(exports) { exports.Lexer = HandlebarsLexer; }

lib/handlebars/jison_ext.js

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+var Lexer = function() {};
+
+Lexer.prototype = {
+  setInput: function(input) {
+    this.input = input;
+    this.yylineno = 0;
+  },
+
+  setupLex: function() {
+    this.yyleng = 0;
+    this.yytext = '';
+  },
+
+  getchar: function(n) {
+    n = n || 1;
+    var char = "";
+
+    for(var i=0; i<n; i++) {
+      char += this.input[0];
+      this.yytext += this.input[0];
+      this.yyleng++;
+
+      if(char === "\n") this.yylineno++;
+
+      this.input = this.input.slice(1);
+    }
+    return char;
+  },
+
+  readchar: function(n) {
+    n = n || 1;
+    var char;
+
+    for(var i=0; i<n; i++) {
+      char = this.input[i];
+      if(char === "\n") this.yylineno++;
+    }
+
+    this.input = this.input.slice(n);
+  },
+
+  peek: function(n) {
+    return this.input.slice(0, n || 1);
+  }
+};
+
+var Visitor = function() {};
+
+Visitor.prototype = {
+  accept: function(object) {
+    return this[object.type](object);
+  }
+}
+
+if(exports) {
+  exports.Lexer = Lexer;
+  exports.Visitor = Visitor;
+}

lib/handlebars/printer.js

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+if(exports) { var Visitor = require("handlebars/jison_ext").Visitor }
+
+PrintVisitor = function() { this.padding = 0; };
+PrintVisitor.prototype = new Visitor;
+
+PrintVisitor.prototype.pad = function(string, newline) {
+  var out = "";
+
+  for(var i=0,l=this.padding; i<l; i++) {
+    out = out + "  ";
+  }
+
+  out = out + string;
+
+  if(newline !== false) { out = out + "\n" }
+  return out;
+};
+
+PrintVisitor.prototype.program = function(program) {
+  var out = this.pad("PROGRAM:"),
+      statements = program.statements,
+      inverse = program.inverse;
+
+  this.padding++;
+
+  for(var i=0, l=statements.length; i<l; i++) {
+    out = out + this.accept(statements[i]);
+  }
+
+  this.padding--;
+
+  if(inverse) {
+    out = out + this.pad("{{^}}");
+
+    this.padding++;
+
+    for(var i=0, l=inverse.length; i<l; i++) {
+      out = out + this.accept(inverse[i]);
+    }
+  }
+
+  this.padding--;
+
+  return out;
+};
+
+PrintVisitor.prototype.block = function(block) {
+  var out = "";
+
+  out = out + this.pad("BLOCK:");
+  this.padding++;
+  out = out + this.accept(block.mustache);
+  out = out + this.accept(block.program);
+  this.padding--;
+
+  return out;
+};
+
+PrintVisitor.prototype.mustache = function(mustache) {
+  var params = mustache.params, paramStrings = [];
+
+  for(var i=0, l=params.length; i<l; i++) {
+    paramStrings.push(this.accept(params[i]));
+  }
+
+  var params = "[" + paramStrings.join(", ") + "]";
+  return this.pad("{{ " + this.accept(mustache.id) + " " + params + "}}");
+};
+
+PrintVisitor.prototype.partial = function(partial) {
+  return this.pad("{{> " + this.accept(partial.id) + " }}");
+};
+
+PrintVisitor.prototype.STRING = function(string) {
+  return string.string;
+};
+
+PrintVisitor.prototype.ID = function(id) {
+  return "ID:" + id.id;
+};
+
+PrintVisitor.prototype.content = function(content) {
+  return this.pad("CONTENT[ '" + content.string + "' ]");
+};
+
+PrintVisitor.prototype.comment = function(comment) {
+  return this.pad("{{! '" + comment.comment + "' }}");
+}
+
+if(exports) {
+  exports.PrintVisitor = PrintVisitor;
+}

src/handlebars.yy

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+%start root
+
+%%
+
+root
+  : program { return $1 }
+  ;
+
+program
+  : statements simpleInverse statements { $$ = new yy.ProgramNode($1, $3) }
+  | statements { $$ = new yy.ProgramNode($1) }
+  ;
+
+statements
+  : statement { $$ = [$1] }
+  | statements statement { $1.push($2); $$ = $1 }
+  ;
+
+statement
+  : openBlock program closeBlock { $$ = new yy.BlockNode($1, $2) }
+  | mustache { $$ = $1 }
+  | partial { $$ = $1 }
+  | CONTENT { $$ = new yy.ContentNode($1) }
+  | COMMENT { $$ = new yy.CommentNode($1) }
+  ;
+
+openBlock
+  : OPEN_BLOCK inMustache CLOSE { $$ = new yy.MustacheNode($2) }
+  ;
+
+closeBlock
+  : OPEN_ENDBLOCK id CLOSE { }
+  ;
+
+mustache
+  : OPEN inMustache CLOSE { $$ = new yy.MustacheNode($2) }
+  ;
+
+partial
+  : OPEN_PARTIAL id CLOSE { $$ = new yy.PartialNode($2) }
+  ;
+
+simpleInverse
+  : OPEN_INVERSE CLOSE { }
+  ;
+
+inMustache
+  : id params { $$ = [$1].concat($2) }
+  | id { $$ = [$1] }
+  ;
+
+params
+  : params param { $1.push($2); $$ = $1; }
+  | param { $$ = [$1] }
+  ;
+
+param
+  : id { $$ = $1 }
+  | STRING { $$ = new yy.StringNode($1) }
+  ;
+
+id
+  : ID { $$ = new yy.IdNode($1) }
+  ;
+

test.js

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+require.paths.push(__dirname + "/lib");
+
+var Handlebars = require("handlebars");
+
+var string = "foo {{ bar baz \"baz\" }}baz{{! foo bar baz }}{{#foo}} bar {{^}} baz {{/foo}}{{> partial }}{{# bar }}part1 {{^}} part2{{> foo }}{{/bar}}zomg"
+
+var ast = Handlebars.parse(string);
+Handlebars.print(ast);