Use Reflect API from xpcshell

parse-mozilla-ast.js

// Reflect API from xpcshell

var Cc = Components.classes;
var Ci = Components.interfaces;
var Cu = Components.utils;

function openFile(aPath) {
    var file = Cc["@mozilla.org/file/local;1"]
            .createInstance(Ci.nsILocalFile);
    file.initWithPath(aPath);

    return file;
}

function readTextFile(aPath, aCharset) {
    var file = openFile(aPath);
    if (!file.exists())
        throw aPath + " not found";

    var fileStream = Cc["@mozilla.org/network/file-input-stream;1"]
            .createInstance(Ci.nsIFileInputStream);
    fileStream.init(file, 1, 0, false);

    var converterStream = Cc["@mozilla.org/intl/converter-input-stream;1"]
            .createInstance(Ci.nsIConverterInputStream);
    if (!aCharset)
        aCharset = 'UTF-8';
    converterStream.init(fileStream, aCharset, fileStream.available(),
                         converterStream.DEFAULT_REPLACEMENT_CHARACTER);
    var out = {};
    converterStream.readString(fileStream.available(), out);

    converterStream.close();
    fileStream.close();

    return out.value;
}

function getSpecialDirectory(prop) {
    var dirService = Cc['@mozilla.org/file/directory_service;1']
            .getService(Ci.nsIProperties);
    return dirService.get(prop, Ci.nsILocalFile);
}

function getFullPathForPWD(relativePath) {
    var curDir = getSpecialDirectory("CurWorkD");
    curDir.appendRelativePath(filePath);
    return curDir.path;
}

function parse(src) {
    var reflect = Cu.import("resource://gre/modules/reflect.jsm");
    var ast = reflect.Reflect.parse(src, { loc: false });
    print(JSON.stringify(ast, null, 2));
}

if (arguments[0]) {
    var filePath = arguments[0];
    var source = readTextFile(getFullPathForPWD(filePath));
    parse(source);
}