meteor/packages/spacebars/spacebars-runtime.js

Spacebars = {};

var tripleEquals = function (a, b) { return a === b; };

Spacebars.include = function (templateOrFunction, contentFunc, elseFunc) {
  if (! templateOrFunction)
    return null;

  if (typeof templateOrFunction !== 'function') {
    var template = templateOrFunction;
    if (! Blaze.isTemplate(template))
      throw new Error("Expected template or null, found: " + template);
    var view = templateOrFunction.constructView(contentFunc, elseFunc);
    view.__startsNewLexicalScope = true;
    return view;
  }

  var templateVar = Blaze.ReactiveVar(null, tripleEquals);
  var view = Blaze.View('Spacebars.include', function () {
    var template = templateVar.get();
    if (template === null)
      return null;

    if (! Blaze.isTemplate(template))
      throw new Error("Expected template or null, found: " + template);

    return template.constructView(contentFunc, elseFunc);
  });
  view.__templateVar = templateVar;
  view.onViewCreated(function () {
    this.autorun(function () {
      templateVar.set(templateOrFunction());
    });
  });
  view.__startsNewLexicalScope = true;

  return view;
};

// Executes `{{foo bar baz}}` when called on `(foo, bar, baz)`.
// If `bar` and `baz` are functions, they are called before
// `foo` is called on them.
//
// This is the shared part of Spacebars.mustache and
// Spacebars.attrMustache, which differ in how they post-process the
// result.
Spacebars.mustacheImpl = function (value/*, args*/) {
  var args = arguments;
  // if we have any arguments (pos or kw), add an options argument
  // if there isn't one.
  if (args.length > 1) {
    var kw = args[args.length - 1];
    if (! (kw instanceof Spacebars.kw)) {
      kw = Spacebars.kw();
      // clone arguments into an actual array, then push
      // the empty kw object.
      args = Array.prototype.slice.call(arguments);
      args.push(kw);
    } else {
      // For each keyword arg, call it if it's a function
      var newHash = {};
      for (var k in kw.hash) {
        var v = kw.hash[k];
        newHash[k] = (typeof v === 'function' ? v() : v);
      }
      args[args.length - 1] = Spacebars.kw(newHash);
    }
  }

  return Spacebars.call.apply(null, args);
};

Spacebars.mustache = function (value/*, args*/) {
  var result = Spacebars.mustacheImpl.apply(null, arguments);

  if (result instanceof Spacebars.SafeString)
    return HTML.Raw(result.toString());
  else
    // map `null`, `undefined`, and `false` to null, which is important
    // so that attributes with nully values are considered absent.
    // stringify anything else (e.g. strings, booleans, numbers including 0).
    return (result == null || result === false) ? null : String(result);
};

Spacebars.attrMustache = function (value/*, args*/) {
  var result = Spacebars.mustacheImpl.apply(null, arguments);

  if (result == null || result === '') {
    return null;
  } else if (typeof result === 'object') {
    return result;
  } else if (typeof result === 'string' && HTML.isValidAttributeName(result)) {
    var obj = {};
    obj[result] = '';
    return obj;
  } else {
    throw new Error("Expected valid attribute name, '', null, or object");
  }
};

Spacebars.dataMustache = function (value/*, args*/) {
  var result = Spacebars.mustacheImpl.apply(null, arguments);

  return result;
};

// Idempotently wrap in `HTML.Raw`.
//
// Called on the return value from `Spacebars.mustache` in case the
// template uses triple-stache (`{{{foo bar baz}}}`).
Spacebars.makeRaw = function (value) {
  if (value == null) // null or undefined
    return null;
  else if (value instanceof HTML.Raw)
    return value;
  else
    return HTML.Raw(value);
};

// If `value` is a function, called it on the `args`, after
// evaluating the args themselves (by calling them if they are
// functions).  Otherwise, simply return `value` (and assert that
// there are no args).
Spacebars.call = function (value/*, args*/) {
  if (typeof value === 'function') {
    // evaluate arguments if they are functions (by calling them)
    var newArgs = [];
    for (var i = 1; i < arguments.length; i++) {
      var arg = arguments[i];
      newArgs[i-1] = (typeof arg === 'function' ? arg() : arg);
    }

    return value.apply(null, newArgs);
  } else {
    if (arguments.length > 1)
      throw new Error("Can't call non-function: " + value);

    return value;
  }
};

// Call this as `Spacebars.kw({ ... })`.  The return value
// is `instanceof Spacebars.kw`.
Spacebars.kw = function (hash) {
  if (! (this instanceof Spacebars.kw))
    // called without new; call with new
    return new Spacebars.kw(hash);

  this.hash = hash || {};
};

// Call this as `Spacebars.SafeString("some HTML")`.  The return value
// is `instanceof Spacebars.SafeString` (and `instanceof Handlebars.SafeString).
Spacebars.SafeString = function (html) {
  if (! (this instanceof Spacebars.SafeString))
    // called without new; call with new
    return new Spacebars.SafeString(html);

  return new Handlebars.SafeString(html);
};
Spacebars.SafeString.prototype = Handlebars.SafeString.prototype;

// `Spacebars.dot(foo, "bar", "baz")` performs a special kind
// of `foo.bar.baz` that allows safe indexing of `null` and
// indexing of functions (which calls the function).  If the
// result is a function, it is always a bound function (e.g.
// a wrapped version of `baz` that always uses `foo.bar` as
// `this`).
//
// In `Spacebars.dot(foo, "bar")`, `foo` is assumed to be either
// a non-function value or a "fully-bound" function wrapping a value,
// where fully-bound means it takes no arguments and ignores `this`.
//
// `Spacebars.dot(foo, "bar")` performs the following steps:
//
// * If `foo` is falsy, return `foo`.
//
// * If `foo` is a function, call it (set `foo` to `foo()`).
//
// * If `foo` is falsy now, return `foo`.
//
// * Return `foo.bar`, binding it to `foo` if it's a function.
Spacebars.dot = function (value, id1/*, id2, ...*/) {
  if (arguments.length > 2) {
    // Note: doing this recursively is probably less efficient than
    // doing it in an iterative loop.
    var argsForRecurse = [];
    argsForRecurse.push(Spacebars.dot(value, id1));
    argsForRecurse.push.apply(argsForRecurse,
                              Array.prototype.slice.call(arguments, 2));
    return Spacebars.dot.apply(null, argsForRecurse);
  }

  if (typeof value === 'function')
    value = value();

  if (! value)
    return value; // falsy, don't index, pass through

  var result = value[id1];
  if (typeof result !== 'function')
    return result;
  // `value[id1]` (or `value()[id1]`) is a function.
  // Bind it so that when called, `value` will be placed in `this`.
  return function (/*arguments*/) {
    return result.apply(value, arguments);
  };
};

// Spacebars.With implements the conditional logic of rendering
// the `{{else}}` block if the argument is falsy.  It combines
// a Blaze.If with a Blaze.With (the latter only in the truthy
// case, since the else block is evaluated without entering
// a new data context).
Spacebars.With = function (argFunc, contentFunc, elseFunc) {
  var argVar = new Blaze.ReactiveVar;
  var view = Blaze.View('Spacebars_with', function () {
    return Blaze.If(function () { return argVar.get(); },
                    function () { return Blaze.With(function () {
                      return argVar.get(); }, contentFunc); },
                    elseFunc);
  });
  view.onViewCreated(function () {
    this.autorun(function () {
      argVar.set(argFunc());

      // This is a hack so that autoruns inside the body
      // of the #with get stopped sooner.  It reaches inside
      // our ReactiveVar to access its dep.

      Tracker.onInvalidate(function () {
        argVar.dep.changed();
      });

      // Take the case of `{{#with A}}{{B}}{{/with}}`.  The goal
      // is to not re-render `B` if `A` changes to become falsy
      // and `B` is simultaneously invalidated.
      //
      // A series of autoruns are involved:
      //
      // 1. This autorun (argument to Spacebars.With)
      // 2. Argument to Blaze.If
      // 3. Blaze.If view re-render
      // 4. Argument to Blaze.With
      // 5. The template tag `{{B}}`
      //
      // When (3) is invalidated, it immediately stops (4) and (5)
      // because of a Tracker.onInvalidate built into materializeView.
      // (When a View's render method is invalidated, it immediately
      // tears down all the subviews, via a Tracker.onInvalidate much
      // like this one.
      //
      // Suppose `A` changes to become falsy, and `B` changes at the
      // same time (i.e. without an intervening flush).
      // Without the code above, this happens:
      //
      // - (1) and (5) are invalidated.
      // - (1) runs, invalidating (2) and (4).
      // - (5) runs.
      // - (2) runs, invalidating (3), stopping (4) and (5).
      //
      // With the code above:
      //
      // - (1) and (5) are invalidated, invalidating (2) and (4).
      // - (1) runs.
      // - (2) runs, invalidating (3), stopping (4) and (5).
      //
      // If the re-run of (5) is originally enqueued before (1), all
      // bets are off, but typically that doesn't seem to be the
      // case.  Anyway, doing this is always better than not doing it,
      // because it might save a bunch of DOM from being updated
      // needlessly.
    });
  });

  return view;
};

// XXX COMPAT WITH 0.9.0
Spacebars.TemplateWith = Blaze._TemplateWith;