This is an ace ide rule that allows for mixed syntax highlighting of handlebars and html in a .html document. (https://github.com/ajaxorg/ace) : Tested here: https://ace.c9.io/tool/mode_creator.html

meteor_highlight_rules.js

define(function(require, exports, module) {
"use strict";

var oop = require("../lib/oop");
var lang = require("../lib/lang");
var CssHighlightRules = require("./css_highlight_rules").CssHighlightRules;
var JavaScriptHighlightRules = require("./javascript_highlight_rules").JavaScriptHighlightRules;
var XmlHighlightRules = require("./xml_highlight_rules").XmlHighlightRules;

var tagMap = lang.createMap({
    a           : 'anchor',
    button 	    : 'form',
    form        : 'form',
    img         : 'image',
    input       : 'form',
    label       : 'form',
    option      : 'form',
    script      : 'script',
    select      : 'form',
    textarea    : 'form',
    style       : 'style',
    table       : 'table',
    tbody       : 'table',
    td          : 'table',
    tfoot       : 'table',
    th          : 'table',
    tr          : 'table'
});

function pop2(currentState, stack) {
    stack.splice(0, 3);
    return stack.shift() || "start";
}

var HtmlHighlightRules = function() {
    XmlHighlightRules.call(this);

    this.addRules({
        attributes: [{
            include : "tag_whitespace"
        }, {
            token : "entity.other.attribute-name.xml",
            regex : "[-_a-zA-Z0-9:.]+"
        }, {
            token : "keyword.operator.attribute-equals.xml",
            regex : "=",
            push : [{
                include: "tag_whitespace"
            }, {
                token : "string.unquoted.attribute-value.html",
                regex : "[^<>='\"`\\s]+",
                next : "pop"
            }, {
                token : "empty",
                regex : "",
                next : "pop"
            }]
        }, {
            include : "attribute_value"
        }],
        tag: [{
            token : function(start, tag) {
                var group = tagMap[tag];
                return ["meta.tag.punctuation." + (start == "<" ? "" : "end-") + "tag-open.xml",
                    "meta.tag" + (group ? "." + group : "") + ".tag-name.xml"];
            },
            regex : "(</?)([-_a-zA-Z0-9:.]+)",
            next: "tag_stuff"
        }],
        tag_stuff: [
            {include : "attributes"},
            {token : "meta.tag.punctuation.tag-close.xml", regex : "/?>", next : "start"}
        ]
    });
    
       var hbs = {
        regex : "(?={{)",
        push : "handlebars"
    };
    
    for (var key in this.$rules) {
        this.$rules[key].unshift(hbs);
    }
    this.$rules.handlebars = [{
        token : "comment.start",
        regex : "{{!--",
        push : [{
            token : "comment.end",
            regex : "--}}",
            next : pop2
        }, {
            defaultToken : "comment"
        }]
    }, {
        token : "comment.start",
        regex : "{{!",
        push : [{
            token : "comment.end",
            regex : "}}",
            next : pop2
        }, {
            defaultToken : "comment"
        }]
    }, {
        token : "support.function", // unescaped variable
        regex : "{{{",
        push : [{
            token : "support.function",
            regex : "}}}",
            next : pop2
        }, {
            token : "variable.parameter",
            regex : "[a-zA-Z_$][a-zA-Z0-9_$]*"
        }]
    }, {
        token : "storage.type.start", // begin section
        regex : "{{[#\\^/&]?",
        push : [{
            token : "storage.type.end",
            regex : "}}",
            next : pop2
        }, {
            token : "variable.parameter",
            regex : "[a-zA-Z_$][a-zA-Z0-9_$]*"
        }]
    }];

    this.embedTagRules(CssHighlightRules, "css-", "style");
    this.embedTagRules(new JavaScriptHighlightRules({noJSX: true}).getRules(), "js-", "script");

    if (this.constructor === HtmlHighlightRules)
        this.normalizeRules();
};

oop.inherits(HtmlHighlightRules, XmlHighlightRules);

exports.HtmlHighlightRules = HtmlHighlightRules;
});