dust-core.js

/*! dustjs-linkedin - v3.0.0
* http://dustjs.com/
* Copyright (c) 2021 Aleksander Williams; Released under the MIT License */
(function (root, factory) {
  if (typeof define === 'function' && define.amd && define.amd.dust === true) {
    define('dust.core', [], factory);
  } else if (typeof exports === 'object') {
    module.exports = factory();
  } else {
    root.dust = factory();
  }
}(this, function() {
  var dust = {
        "version": "3.0.0"
      },
      NONE = 'NONE', ERROR = 'ERROR', WARN = 'WARN', INFO = 'INFO', DEBUG = 'DEBUG',
      EMPTY_FUNC = function() {};

  dust.config = {
    whitespace: false,
    amd: false,
    cjs: false,
    cache: true
  };

  // Directive aliases to minify code
  dust._aliases = {
    "write": "w",
    "end": "e",
    "map": "m",
    "render": "r",
    "reference": "f",
    "section": "s",
    "exists": "x",
    "notexists": "nx",
    "block": "b",
    "partial": "p",
    "helper": "h"
  };

  (function initLogging() {
    /*global process, console*/
    var loggingLevels = { DEBUG: 0, INFO: 1, WARN: 2, ERROR: 3, NONE: 4 },
        consoleLog,
        log;

    if (typeof console !== 'undefined' && console.log) {
      consoleLog = console.log;
      if(typeof consoleLog === 'function') {
        log = function() {
          consoleLog.apply(console, arguments);
        };
      } else {
        log = function() {
          consoleLog(Array.prototype.slice.apply(arguments).join(' '));
        };
      }
    } else {
      log = EMPTY_FUNC;
    }

    /**
     * Filters messages based on `dust.debugLevel`.
     * This default implementation will print to the console if it exists.
     * @param {String|Error} message the message to print/throw
     * @param {String} type the severity of the message(ERROR, WARN, INFO, or DEBUG)
     * @public
     */
    dust.log = function(message, type) {
      type = type || INFO;
      if (loggingLevels[type] >= loggingLevels[dust.debugLevel]) {
        log('[DUST:' + type + ']', message);
        if (type === ERROR && dust.debugLevel === DEBUG && message instanceof Error && message.stack) {
          log('[DUST:' + type + ']', message.stack);
        }
      }
    };

    dust.debugLevel = NONE;
    if(typeof process !== 'undefined' && process.env && /\bdust\b/.test(process.env.DEBUG)) {
      dust.debugLevel = DEBUG;
    }

  }());

  dust.helpers = {};

  dust.cache = {};

  dust.register = function(name, tmpl) {
    if (!name) {
      return;
    }
    tmpl.templateName = name;
    if (dust.config.cache !== false) {
      dust.cache[name] = tmpl;
    }
  };

  dust.render = function(nameOrTemplate, context, callback) {
    var chunk = new Stub(callback).head;
    try {
      load(nameOrTemplate, chunk, context).end();
    } catch (err) {
      chunk.setError(err);
    }
  };

  dust.stream = function(nameOrTemplate, context) {
    var stream = new Stream(),
        chunk = stream.head;
    dust.nextTick(function() {
      try {
        load(nameOrTemplate, chunk, context).end();
      } catch (err) {
        chunk.setError(err);
      }
    });
    return stream;
  };

  /**
   * Extracts a template function (body_0) from whatever is passed.
   * @param nameOrTemplate {*} Could be:
   *   - the name of a template to load from cache
   *   - a CommonJS-compiled template (a function with a `template` property)
   *   - a template function
   * @param loadFromCache {Boolean} if false, don't look in the cache
   * @return {Function} a template function, if found
   */
  function getTemplate(nameOrTemplate, loadFromCache/*=true*/) {
    if(!nameOrTemplate) {
      return;
    }
    if(typeof nameOrTemplate === 'function' && nameOrTemplate.template) {
      // Sugar away CommonJS module templates
      return nameOrTemplate.template;
    }
    if(dust.isTemplateFn(nameOrTemplate)) {
      // Template functions passed directly
      return nameOrTemplate;
    }
    if(loadFromCache !== false) {
      // Try loading a template with this name from cache
      return dust.cache[nameOrTemplate];
    }
  }

  function load(nameOrTemplate, chunk, context) {
    if(!nameOrTemplate) {
      return chunk.setError(new Error('No template or template name provided to render'));
    }

    var template = getTemplate(nameOrTemplate, dust.config.cache);

    if (template) {
      return template(chunk, Context.wrap(context, template.templateName));
    } else {
      if (dust.onLoad) {
        return chunk.map(function(chunk) {
          // Alias just so it's easier to read that this would always be a name
          var name = nameOrTemplate;
          // Three possible scenarios for a successful callback:
          //   - `require(nameOrTemplate)(dust); cb()`
          //   - `src = readFile('src.dust'); cb(null, src)`
          //   - `compiledTemplate = require(nameOrTemplate)(dust); cb(null, compiledTemplate)`
          function done(err, srcOrTemplate) {
            var template;
            if (err) {
              return chunk.setError(err);
            }
            // Prefer a template that is passed via callback over the cached version.
            template = getTemplate(srcOrTemplate, false) || getTemplate(name, dust.config.cache);
            if (!template) {
              // It's a template string, compile it and register under `name`
              if(dust.compile) {
                template = dust.loadSource(dust.compile(srcOrTemplate, name));
              } else {
                return chunk.setError(new Error('Dust compiler not available'));
              }
            }
            template(chunk, Context.wrap(context, template.templateName)).end();
          }

          if(dust.onLoad.length === 3) {
            dust.onLoad(name, context.options, done);
          } else {
            dust.onLoad(name, done);
          }
        });
      }
      return chunk.setError(new Error('Template Not Found: ' + nameOrTemplate));
    }
  }

  dust.loadSource = function(source) {
    /*jshint evil:true*/
    return eval(source);
  };

  if (Array.isArray) {
    dust.isArray = Array.isArray;
  } else {
    dust.isArray = function(arr) {
      return Object.prototype.toString.call(arr) === '[object Array]';
    };
  }

  dust.nextTick = (function() {
    return function(callback) {
      setTimeout(callback, 0);
    };
  })();

  /**
   * Dust has its own rules for what is "empty"-- which is not the same as falsy.
   * Empty arrays, null, and undefined are empty
   */
  dust.isEmpty = function(value) {
    if (value === 0) {
      return false;
    }
    if (dust.isArray(value) && !value.length) {
      return true;
    }
    return !value;
  };

  dust.isEmptyObject = function(obj) {
    var key;
    if (obj === null) {
      return false;
    }
    if (obj === undefined) {
      return false;
    }
    if (obj.length > 0) {
      return false;
    }
    for (key in obj) {
      if (Object.prototype.hasOwnProperty.call(obj, key)) {
        return false;
      }
    }
    return true;
  };

  dust.isTemplateFn = function(elem) {
    return typeof elem === 'function' &&
           elem.__dustBody;
  };

  /**
   * Decide somewhat-naively if something is a Thenable.  Matches Promises A+ Spec, section 1.2 “thenable” is an object or function that defines a then method."
   * @param elem {*} object to inspect
   * @return {Boolean} is `elem` a Thenable?
   */
  dust.isThenable = function(elem) {
    return elem &&  /* Beware: `typeof null` is `object` */
           (typeof elem === 'object' || typeof elem === 'function') &&
           typeof elem.then === 'function';
  };

  /**
   * Decide if an element is a function but not Thenable; it is prefereable to resolve a thenable function by its `.then` method.
   * @param elem {*} target of inspection
   * @return {Boolean} is `elem` a function without a `.then` property?
   */
  dust.isNonThenableFunction = function(elem) {
    return typeof elem === 'function' && !dust.isThenable(elem);
  };

  /**
   * Decide very naively if something is a Stream.
   * @param elem {*} object to inspect
   * @return {Boolean} is `elem` a Stream?
   */
  dust.isStreamable = function(elem) {
    return elem &&
           typeof elem.on === 'function' &&
           typeof elem.pipe === 'function';
  };

  // apply the filter chain and return the output string
  dust.filter = function(string, auto, filters, context) {
    var i, len, name, filter;
    if (filters) {
      for (i = 0, len = filters.length; i < len; i++) {
        name = filters[i];
        if (!name.length) {
          continue;
        }
        filter = dust.filters[name];
        if (name === 's') {
          auto = null;
        } else if (typeof filter === 'function') {
          string = filter(string, context);
        } else {
          dust.log('Invalid filter `' + name + '`', WARN);
        }
      }
    }
    // by default always apply the h filter, unless asked to unescape with |s
    if (auto) {
      string = dust.filters[auto](string, context);
    }
    return string;
  };

  dust.filters = {
    h: function(value) { return dust.escapeHtml(value); },
    j: function(value) { return dust.escapeJs(value); },
    u: encodeURI,
    uc: encodeURIComponent,
    js: function(value) { return dust.escapeJSON(value); },
    jp: function(value) {
      if (!JSON) {dust.log('JSON is undefined; could not parse `' + value + '`', WARN);
        return value;
      } else {
        return JSON.parse(value);
      }
    }
  };

  function Context(stack, global, options, blocks, templateName) {
    if(stack !== undefined && !(stack instanceof Stack)) {
      stack = new Stack(stack);
    }
    this.stack = stack;
    this.global = global;
    this.options = options;
    this.blocks = blocks;
    this.templateName = templateName;
    this._isContext = true;
  }

  dust.makeBase = dust.context = function(global, options) {
    return new Context(undefined, global, options);
  };

  dust.isContext = function(obj) {
    return typeof obj === "object" && obj._isContext === true;
  };

  /**
   * Factory function that creates a closure scope around a Thenable-callback.
   * Returns a function that can be passed to a Thenable that will resume a
   * Context lookup once the Thenable resolves with new data, adding that new
   * data to the lookup stack.
   */
  function getWithResolvedData(ctx, cur, down) {
    return function(data) {
      return ctx.push(data)._get(cur, down);
    };
  }

  Context.wrap = function(context, name) {
    if (dust.isContext(context)) {
      context.templateName = name;
      return context;
    }
    return new Context(context, {}, {}, null, name);
  };

  /**
   * Public API for getting a value from the context.
   * @method get
   * @param {string|array} path The path to the value. Supported formats are:
   * 'key'
   * 'path.to.key'
   * '.path.to.key'
   * ['path', 'to', 'key']
   * ['key']
   * @param {boolean} [cur=false] Boolean which determines if the search should be limited to the
   * current context (true), or if get should search in parent contexts as well (false).
   * @public
   * @returns {string|object}
   */
  Context.prototype.get = function(path, cur) {
    if (typeof path === 'string') {
      if (path[0] === '.') {
        cur = true;
        path = path.substr(1);
      }
      path = path.split('.');
    }
    return this._get(cur, path);
  };

  /**
   * Get a value from the context
   * @method _get
   * @param {boolean} cur Get only from the current context
   * @param {array} down An array of each step in the path
   * @private
   * @return {string | object}
   */
  Context.prototype._get = function(cur, down) {
    var ctx = this.stack || {},
        i = 1,
        value, first, len, ctxThis, fn;

    first = down[0];
    len = down.length;

    if (cur && len === 0) {
      ctxThis = ctx;
      ctx = ctx.head;
    } else {
      if (!cur) {
        // Search up the stack for the first value
        while (ctx) {
          if (ctx.isObject) {
            ctxThis = ctx.head;
            value = ctx.head[first];
            if (value !== undefined) {
              break;
            }
          }
          ctx = ctx.tail;
        }

        // Try looking in the global context if we haven't found anything yet
        if (value !== undefined) {
          ctx = value;
        } else {
          ctx = this.global && this.global[first];
        }
      } else if (ctx) {
        // if scope is limited by a leading dot, don't search up the tree
        if(ctx.head) {
          ctx = ctx.head[first];
        } else {
          // context's head is empty, value we are searching for is not defined
          ctx = undefined;
        }
      }

      while (ctx && i < len) {
        if (dust.isThenable(ctx)) {
          // Bail early by returning a Thenable for the remainder of the search tree
          return ctx.then(getWithResolvedData(this, cur, down.slice(i)));
        }
        ctxThis = ctx;
        ctx = ctx[down[i]];
        i++;
      }
    }

    if (dust.isNonThenableFunction(ctx)) {
      fn = function() {
        try {
          return ctx.apply(ctxThis, arguments);
        } catch (err) {
          dust.log(err, ERROR);
          throw err;
        }
      };
      fn.__dustBody = !!ctx.__dustBody;
      return fn;
    } else {
      if (ctx === undefined) {
        dust.log('Cannot find reference `{' + down.join('.') + '}` in template `' + this.getTemplateName() + '`', INFO);
      }
      return ctx;
    }
  };

  Context.prototype.getPath = function(cur, down) {
    return this._get(cur, down);
  };

  Context.prototype.push = function(head, idx, len) {
    if(head === undefined) {
      dust.log("Not pushing an undefined variable onto the context", INFO);
      return this;
    }
    return this.rebase(new Stack(head, this.stack, idx, len));
  };

  Context.prototype.pop = function() {
    var head = this.current();
    this.stack = this.stack && this.stack.tail;
    return head;
  };

  Context.prototype.rebase = function(head) {
    return new Context(head, this.global, this.options, this.blocks, this.getTemplateName());
  };

  Context.prototype.clone = function() {
    var context = this.rebase();
    context.stack = this.stack;
    return context;
  };

  Context.prototype.current = function() {
    return this.stack && this.stack.head;
  };

  Context.prototype.getBlock = function(key) {
    var blocks, len, fn;

    if (typeof key === 'function') {
      key = key(new Chunk(), this).data.join('');
    }

    blocks = this.blocks;

    if (!blocks) {
      dust.log('No blocks for context `' + key + '` in template `' + this.getTemplateName() + '`', DEBUG);
      return false;
    }

    len = blocks.length;
    while (len--) {
      fn = blocks[len][key];
      if (fn) {
        return fn;
      }
    }

    dust.log('Malformed template `' + this.getTemplateName() + '` was missing one or more blocks.');
    return false;
  };

  Context.prototype.shiftBlocks = function(locals) {
    var blocks = this.blocks,
        newBlocks;

    if (locals) {
      if (!blocks) {
        newBlocks = [locals];
      } else {
        newBlocks = blocks.concat([locals]);
      }
      return new Context(this.stack, this.global, this.options, newBlocks, this.getTemplateName());
    }
    return this;
  };

  Context.prototype.resolve = function(body) {
    var chunk;

    if(typeof body !== 'function') {
      return body;
    }
    chunk = new Chunk().render(body, this);
    if(chunk instanceof Chunk) {
      return chunk.data.join(''); // ie7 perf
    }
    return chunk;
  };

  Context.prototype.getTemplateName = function() {
    return this.templateName;
  };

  function Stack(head, tail, idx, len) {
    this.tail = tail;
    this.isObject = head && typeof head === 'object';
    this.head = head;
    this.index = idx;
    this.of = len;
  }

  function Stub(callback) {
    this.head = new Chunk(this);
    this.callback = callback;
    this.out = '';
  }

  Stub.prototype.flush = function() {
    var chunk = this.head;

    while (chunk) {
      if (chunk.flushable) {
        this.out += chunk.data.join(''); //ie7 perf
      } else if (chunk.error) {
        this.callback(chunk.error);
        dust.log('Rendering failed with error `' + chunk.error + '`', ERROR);
        this.flush = EMPTY_FUNC;
        return;
      } else {
        return;
      }
      chunk = chunk.next;
      this.head = chunk;
    }
    this.callback(null, this.out);
  };

  /**
   * Creates an interface sort of like a Streams2 ReadableStream.
   */
  function Stream() {
    this.head = new Chunk(this);
  }

  Stream.prototype.flush = function() {
    var chunk = this.head;

    while(chunk) {
      if (chunk.flushable) {
        this.emit('data', chunk.data.join('')); //ie7 perf
      } else if (chunk.error) {
        this.emit('error', chunk.error);
        this.emit('end');
        dust.log('Streaming failed with error `' + chunk.error + '`', ERROR);
        this.flush = EMPTY_FUNC;
        return;
      } else {
        return;
      }
      chunk = chunk.next;
      this.head = chunk;
    }
    this.emit('end');
  };

  /**
   * Executes listeners for `type` by passing data. Note that this is different from a
   * Node stream, which can pass an arbitrary number of arguments
   * @return `true` if event had listeners, `false` otherwise
   */
  Stream.prototype.emit = function(type, data) {
    var events = this.events || {},
        handlers = events[type] || [],
        i, l;

    if (!handlers.length) {
      dust.log('Stream broadcasting, but no listeners for `' + type + '`', DEBUG);
      return false;
    }

    handlers = handlers.slice(0);
    for (i = 0, l = handlers.length; i < l; i++) {
      handlers[i](data);
    }
    return true;
  };

  Stream.prototype.on = function(type, callback) {
    var events = this.events = this.events || {},
        handlers = events[type] = events[type] || [];

    if(typeof callback !== 'function') {
      dust.log('No callback function provided for `' + type + '` event listener', WARN);
    } else {
      handlers.push(callback);
    }
    return this;
  };

  /**
   * Pipes to a WritableStream. Note that backpressure isn't implemented,
   * so we just write as fast as we can.
   * @param stream {WritableStream}
   * @return self
   */
  Stream.prototype.pipe = function(stream) {
    if(typeof stream.write !== 'function' ||
       typeof stream.end !== 'function') {
      dust.log('Incompatible stream passed to `pipe`', WARN);
      return this;
    }

    var destEnded = false;

    if(typeof stream.emit === 'function') {
      stream.emit('pipe', this);
    }

    if(typeof stream.on === 'function') {
      stream.on('error', function() {
        destEnded = true;
      });
    }

    return this
    .on('data', function(data) {
      if(destEnded) {
        return;
      }
      try {
        stream.write(data, 'utf8');
      } catch (err) {
        dust.log(err, ERROR);
      }
    })
    .on('end', function() {
      if(destEnded) {
        return;
      }
      try {
        stream.end();
        destEnded = true;
      } catch (err) {
        dust.log(err, ERROR);
      }
    });
  };

  function Chunk(root, next, taps) {
    this.root = root;
    this.next = next;
    this.data = []; //ie7 perf
    this.flushable = false;
    this.taps = taps;
  }

  Chunk.prototype.write = function(data) {
    var taps = this.taps;

    if (taps) {
      data = taps.go(data);
    }
    this.data.push(data);
    return this;
  };

  Chunk.prototype.end = function(data) {
    if (data) {
      this.write(data);
    }
    this.flushable = true;
    this.root.flush();
    return this;
  };

  /**
   * Inserts a new chunk that can be used to asynchronously render or write to it
   * @param callback {Function} The function that will be called with the new chunk
   * @returns {Chunk} A copy of this chunk instance in order to further chain function calls on the chunk
   */
  Chunk.prototype.map = function(callback) {
    var cursor = new Chunk(this.root, this.next, this.taps),
        branch = new Chunk(this.root, cursor, this.taps);

    this.next = branch;
    this.flushable = true;
    try {
      callback(branch);
    } catch(err) {
      dust.log(err, ERROR);
      branch.setError(err);
    }
    return cursor;
  };

  /**
   * Like Chunk#map but additionally resolves a thenable.  If the thenable succeeds the callback is invoked with
   * a new chunk that can be used to asynchronously render or write to it, otherwise if the thenable is rejected
   * then the error body is rendered if available, an error is logged, and the callback is never invoked.
   * @param {Chunk} The current chunk to insert a new chunk
   * @param thenable {Thenable} the target thenable to await
   * @param context {Context} context to use to render the deferred chunk
   * @param bodies {Object} may optionally contain an "error" for when the thenable is rejected
   * @param callback {Function} The function that will be called with the new chunk
   * @returns {Chunk} A copy of this chunk instance in order to further chain function calls on the chunk
   */
  function mapThenable(chunk, thenable, context, bodies, callback) {
    return chunk.map(function(asyncChunk) {
      thenable.then(function(data) {
        try {
          callback(asyncChunk, data);
        } catch (err) {
          // handle errors the same way Chunk#map would.  This logic is only here since the thenable defers
          // logic such that the try / catch in Chunk#map would not capture it.
          dust.log(err, ERROR);
          asyncChunk.setError(err);
        }
      }, function(err) {
        dust.log('Unhandled promise rejection in `' + context.getTemplateName() + '`', INFO);
        asyncChunk.renderError(err, context, bodies).end();
      });
    });
  }

  Chunk.prototype.tap = function(tap) {
    var taps = this.taps;

    if (taps) {
      this.taps = taps.push(tap);
    } else {
      this.taps = new Tap(tap);
    }
    return this;
  };

  Chunk.prototype.untap = function() {
    this.taps = this.taps.tail;
    return this;
  };

  Chunk.prototype.render = function(body, context) {
    return body(this, context);
  };

  Chunk.prototype.reference = function(elem, context, auto, filters) {
    if (dust.isNonThenableFunction(elem)) {
      elem = elem.apply(context.current(), [this, context, null, {auto: auto, filters: filters}]);
      if (elem instanceof Chunk) {
        return elem;
      } else {
        return this.reference(elem, context, auto, filters);
      }
    }
    if (dust.isThenable(elem)) {
      return this.await(elem, context, null, auto, filters);
    } else if (dust.isStreamable(elem)) {
      return this.stream(elem, context, null, auto, filters);
    } else if (!dust.isEmpty(elem)) {
      return this.write(dust.filter(elem, auto, filters, context));
    } else {
      return this;
    }
  };

  Chunk.prototype.section = function(elem, context, bodies, params) {
    var body = bodies.block,
        skip = bodies['else'],
        chunk = this,
        i, len, head;

    if (dust.isNonThenableFunction(elem) && !dust.isTemplateFn(elem)) {
      try {
        elem = elem.apply(context.current(), [this, context, bodies, params]);
      } catch(err) {
        dust.log(err, ERROR);
        return this.setError(err);
      }
      // Functions that return chunks are assumed to have handled the chunk manually.
      // Make that chunk the current one and go to the next method in the chain.
      if (elem instanceof Chunk) {
        return elem;
      }
    }

    if (dust.isEmptyObject(bodies)) {
      // No bodies to render, and we've already invoked any function that was available in
      // hopes of returning a Chunk.
      return chunk;
    }

    if (!dust.isEmptyObject(params)) {
      context = context.push(params);
    }

    /*
    Dust's default behavior is to enumerate over the array elem, passing each object in the array to the block.
    When elem resolves to a value or object instead of an array, Dust sets the current context to the value
    and renders the block one time.
    */
    if (dust.isArray(elem)) {
      if (body) {
        len = elem.length;
        if (len > 0) {
          head = context.stack && context.stack.head || {};
          head.$len = len;
          for (i = 0; i < len; i++) {
            head.$idx = i;
            chunk = body(chunk, context.push(elem[i], i, len));
          }
          head.$idx = undefined;
          head.$len = undefined;
          return chunk;
        } else if (skip) {
          return skip(this, context);
        }
      }
    } else if (dust.isThenable(elem)) {
      return this.await(elem, context, bodies);
    } else if (dust.isStreamable(elem)) {
      return this.stream(elem, context, bodies);
    } else if (elem === true) {
     // true is truthy but does not change context
      if (body) {
        return body(this, context);
      }
    } else if (elem || elem === 0) {
       // everything that evaluates to true are truthy ( e.g. Non-empty strings and Empty objects are truthy. )
       // zero is truthy
       // for anonymous functions that did not returns a chunk, truthiness is evaluated based on the return value
      if (body) {
        return body(this, context.push(elem));
      }
     // nonexistent, scalar false value, scalar empty string, null,
     // undefined are all falsy
    } else if (skip) {
      return skip(this, context);
    }
    dust.log('Section without corresponding key in template `' + context.getTemplateName() + '`', DEBUG);
    return this;
  };

  Chunk.prototype.exists = function(elem, context, bodies) {
    var body = bodies.block,
        skip = bodies['else'];

    if (dust.isThenable(elem)) {
      return mapThenable(this, elem, context, bodies, function(chunk, data) {
        chunk.exists(data, context, bodies).end();
      });
    }

    if (!dust.isEmpty(elem)) {
      if (body) {
        return body(this, context);
      }
      dust.log('No block for exists check in template `' + context.getTemplateName() + '`', DEBUG);
    } else if (skip) {
      return skip(this, context);
    }
    return this;
  };

  Chunk.prototype.notexists = function(elem, context, bodies) {
    var body = bodies.block,
        skip = bodies['else'];

    if (dust.isThenable(elem)) {
      return mapThenable(this, elem, context, bodies, function(chunk, data) {
        chunk.notexists(data, context, bodies).end();
      });
    }

    if (dust.isEmpty(elem)) {
      if (body) {
        return body(this, context);
      }
      dust.log('No block for not-exists check in template `' + context.getTemplateName() + '`', DEBUG);
    } else if (skip) {
      return skip(this, context);
    }
    return this;
  };

  Chunk.prototype.block = function(elem, context, bodies) {
    var body = elem || bodies.block;

    if (body) {
      return body(this, context);
    }
    return this;
  };

  Chunk.prototype.partial = function(elem, context, partialContext, params) {
    var head;

    if(params === undefined) {
      // Compatibility for < 2.7.0 where `partialContext` did not exist
      params = partialContext;
      partialContext = context;
    }

    if (!dust.isEmptyObject(params)) {
      partialContext = partialContext.clone();
      head = partialContext.pop();
      partialContext = partialContext.push(params)
                                     .push(head);
    }

    if (dust.isTemplateFn(elem)) {
      // The eventual result of evaluating `elem` is a partial name
      // Load the partial after getting its name and end the async chunk
      return this.capture(elem, context, function(name, chunk) {
        load(name, chunk, partialContext).end();
      });
    } else {
      return load(elem, this, partialContext);
    }
  };

  Chunk.prototype.helper = function(name, context, bodies, params, auto) {
    var chunk = this,
        filters = params.filters,
        ret;

    // Pre-2.7.1 compat: if auto is undefined, it's an old template. Automatically escape
    if (auto === undefined) {
      auto = 'h';
    }

    // handle invalid helpers, similar to invalid filters
    if(dust.helpers[name]) {
      try {
        ret = dust.helpers[name](chunk, context, bodies, params);
        if (ret instanceof Chunk) {
          return ret;
        }
        if(typeof filters === 'string') {
          filters = filters.split('|');
        }
        if (!dust.isEmptyObject(bodies)) {
          return chunk.section(ret, context, bodies, params);
        }
        // Helpers act slightly differently from functions in context in that they will act as
        // a reference if they are self-closing (due to grammar limitations)
        // In the Chunk.await function we check to make sure bodies is null before acting as a reference
        return chunk.reference(ret, context, auto, filters);
      } catch(err) {
        dust.log('Error in helper `' + name + '`: ' + err.message, ERROR);
        return chunk.setError(err);
      }
    } else {
      dust.log('Helper `' + name + '` does not exist', WARN);
      return chunk;
    }
  };

  /**
   * Reserve a chunk to be evaluated once a thenable is resolved or rejected
   * @param thenable {Thenable} the target thenable to await
   * @param context {Context} context to use to render the deferred chunk
   * @param bodies {Object} must contain a "body", may contain an "error"
   * @param auto {String} automatically apply this filter if the Thenable is a reference
   * @param filters {Array} apply these filters if the Thenable is a reference
   * @return {Chunk}
   */
  Chunk.prototype.await = function(thenable, context, bodies, auto, filters) {
    return mapThenable(this, thenable, context, bodies, function(chunk, data) {
      if (bodies) {
        chunk.section(data, context, bodies).end();
      } else {
        // Actually a reference. Self-closing sections don't render
        chunk.reference(data, context, auto, filters).end();
      }
    });
  };

  /**
   * Render an error body if available
   * @param err {Error} error that occurred
   * @param context {Context} context to use to render the error
   * @param bodies {Object} may optionally contain an "error" which will be rendered
   * @return {Chunk}
   */
  Chunk.prototype.renderError = function(err, context, bodies) {
    var errorBody = bodies && bodies.error;
    if (errorBody) {
      return this.render(errorBody, context.push(err));
    }
    return this;
  };

  /**
   * Reserve a chunk to be evaluated with the contents of a streamable.
   * Currently an error event will bomb out the stream. Once an error
   * is received, we push it to an {:error} block if one exists, and log otherwise,
   * then stop listening to the stream.
   * @param streamable {Streamable} the target streamable that will emit events
   * @param context {Context} context to use to render each thunk
   * @param bodies {Object} must contain a "body", may contain an "error"
   * @return {Chunk}
   */
  Chunk.prototype.stream = function(stream, context, bodies, auto, filters) {
    var body = bodies && bodies.block;
    return this.map(function(chunk) {
      var ended = false;
      stream
        .on('data', function data(thunk) {
          if(ended) {
            return;
          }
          if(body) {
            // Fork a new chunk out of the blockstream so that we can flush it independently
            chunk = chunk.map(function(chunk) {
              chunk.render(body, context.push(thunk)).end();
            });
          } else if(!bodies) {
            // When actually a reference, don't fork, just write into the master async chunk
            chunk = chunk.reference(thunk, context, auto, filters);
          }
        })
        .on('error', function error(err) {
          if(ended) {
            return;
          }
          chunk.renderError(err, context, bodies);
          dust.log('Unhandled stream error in `' + context.getTemplateName() + '`', INFO);
          if(!ended) {
            ended = true;
            chunk.end();
          }
        })
        .on('end', function end() {
          if(!ended) {
            ended = true;
            chunk.end();
          }
        });
    });
  };

  Chunk.prototype.capture = function(body, context, callback) {
    return this.map(function(chunk) {
      var stub = new Stub(function(err, out) {
        if (err) {
          chunk.setError(err);
        } else {
          callback(out, chunk);
        }
      });
      body(stub.head, context).end();
    });
  };

  Chunk.prototype.setError = function(err) {
    this.error = err;
    this.root.flush();
    return this;
  };

  // Chunk aliases
  for(var f in Chunk.prototype) {
    if(dust._aliases[f]) {
      Chunk.prototype[dust._aliases[f]] = Chunk.prototype[f];
    }
  }

  function Tap(head, tail) {
    this.head = head;
    this.tail = tail;
  }

  Tap.prototype.push = function(tap) {
    return new Tap(tap, this);
  };

  Tap.prototype.go = function(value) {
    var tap = this;

    while(tap) {
      value = tap.head(value);
      tap = tap.tail;
    }
    return value;
  };

  var HCHARS = /[&<>"']/,
      AMP    = /&/g,
      LT     = /</g,
      GT     = />/g,
      QUOT   = /\"/g,
      SQUOT  = /\'/g;

  dust.escapeHtml = function(s) {
    if (typeof s === "string" || (s && typeof s.toString === "function")) {
      if (typeof s !== "string") {
        s = s.toString();
      }
      if (!HCHARS.test(s)) {
        return s;
      }
      return s.replace(AMP,'&amp;').replace(LT,'&lt;').replace(GT,'&gt;').replace(QUOT,'&quot;').replace(SQUOT, '&#39;');
    }
    return s;
  };

  var BS = /\\/g,
      FS = /\//g,
      CR = /\r/g,
      LS = /\u2028/g,
      PS = /\u2029/g,
      NL = /\n/g,
      LF = /\f/g,
      SQ = /'/g,
      DQ = /"/g,
      TB = /\t/g;

  dust.escapeJs = function(s) {
    if (typeof s === 'string') {
      return s
        .replace(BS, '\\\\')
        .replace(FS, '\\/')
        .replace(DQ, '\\"')
        .replace(SQ, '\\\'')
        .replace(CR, '\\r')
        .replace(LS, '\\u2028')
        .replace(PS, '\\u2029')
        .replace(NL, '\\n')
        .replace(LF, '\\f')
        .replace(TB, '\\t');
    }
    return s;
  };

  dust.escapeJSON = function(o) {
    if (!JSON) {
      dust.log('JSON is undefined; could not escape `' + o + '`', WARN);
      return o;
    } else {
      return JSON.stringify(o)
        .replace(LS, '\\u2028')
        .replace(PS, '\\u2029')
        .replace(LT, '\\u003c');
    }
  };

  return dust;

}));

if (typeof define === "function" && define.amd && define.amd.dust === true) {
    define(["require", "dust.core"], function(require, dust) {
        dust.onLoad = function(name, cb) {
            require([name], function(tmpl) {
                cb(null, tmpl);
            });
        };
        return dust;
    });
}