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Commit 76d2910

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Scott J. Miles
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prevent stackoverflow when calling a non-existent superclass method
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‎src/lib/super.js

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/*
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* Copyright 2013 The Polymer Authors. All rights reserved.
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* Use of this source code is governed by a BSD-style
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* license that can be found in the LICENSE file.
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*/
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(function(scope) {
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// super
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// `arrayOfArgs` is an optional array of args like one might pass
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// to `Function.apply`
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// TODO(sjmiles):
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// $super must be installed on an instance or prototype chain
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// as `super`, and invoked via `this`, e.g.
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// `this.super();`
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// will not work if function objects are not unique, for example,
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// when using mixins.
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// The memoization strategy assumes each function exists on only one
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// prototype chain i.e. we use the function object for memoizing)
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// perhaps we can bookkeep on the prototype itself instead
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function $super(arrayOfArgs) {
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// since we are thunking a method call, performance is important here:
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// memoize all lookups, once memoized the fast path calls no other
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// functions
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//
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// find the caller (cannot be `strict` because of 'caller')
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var caller = $super.caller;
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// memoized 'name of method'
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var nom = caller.nom;
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// memoized next implementation prototype
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var _super = caller._super;
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if (!_super) {
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if (!nom) {
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nom = caller.nom = nameInThis.call(this, caller);
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}
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if (!nom) {
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console.warn('called super() on a method not installed declaratively (has no .nom property)');
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}
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// super prototype is either cached or we have to find it
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// by searching __proto__ (at the 'top')
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_super = memoizeSuper(caller, nom, getPrototypeOf(this));
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}
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if (!_super) {
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// if _super is falsey, there is no super implementation
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//console.warn('called $super(' + nom + ') where there is no super implementation');
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} else {
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// our super function
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var fn = _super[nom];
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// memoize information so 'fn' can call 'super'
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if (!fn._super) {
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memoizeSuper(fn, nom, _super);
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}
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// invoke the inherited method
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// if 'fn' is not function valued, this will throw
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return fn.apply(this, arrayOfArgs || []);
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}
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}
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function nextSuper(proto, name, caller) {
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// look for an inherited prototype that implements name
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while (proto) {
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if ((proto[name] !== caller) && proto[name]) {
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return proto;
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}
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proto = getPrototypeOf(proto);
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}
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}
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function memoizeSuper(method, name, proto) {
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// find and cache next prototype containing `name`
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// we need the prototype so we can do another lookup
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// from here
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method._super = nextSuper(proto, name, method);
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if (method._super) {
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// _super is a prototype, the actual method is _super[name]
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// tag super method with it's name for further lookups
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method._super[name].nom = name;
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}
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return method._super;
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}
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function nameInThis(value) {
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var p = this.__proto__;
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while (p && p !== HTMLElement.prototype) {
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// TODO(sjmiles): getOwnPropertyNames is absurdly expensive
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var n$ = Object.getOwnPropertyNames(p);
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for (var i=0, l=n$.length, n; i<l && (n=n$[i]); i++) {
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var d = Object.getOwnPropertyDescriptor(p, n);
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if (typeof d.value === 'function' && d.value === value) {
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return n;
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}
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}
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p = p.__proto__;
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}
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}
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// NOTE: In some platforms (IE10) the prototype chain is faked via
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// __proto__. Therefore, always get prototype via __proto__ instead of
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// the more standard Object.getPrototypeOf.
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function getPrototypeOf(prototype) {
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return prototype.__proto__;
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}
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// utility function to precompute name tags for functions
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// in a (unchained) prototype
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function hintSuper(prototype) {
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// tag functions with their prototype name to optimize
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// super call invocations
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for (var n in prototype) {
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var pd = Object.getOwnPropertyDescriptor(prototype, n);
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if (pd && typeof pd.value === 'function') {
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pd.value.nom = n;
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}
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}
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}
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// exports
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scope.super = $super;
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})(Polymer);
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/*
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* Copyright 2013 The Polymer Authors. All rights reserved.
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* Use of this source code is governed by a BSD-style
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* license that can be found in the LICENSE file.
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*/
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(function(scope) {
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// super
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// `arrayOfArgs` is an optional array of args like one might pass
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// to `Function.apply`
11+
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// TODO(sjmiles):
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// $super must be installed on an instance or prototype chain
14+
// as `super`, and invoked via `this`, e.g.
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// `this.super();`
16+
17+
// will not work if function objects are not unique, for example,
18+
// when using mixins.
19+
// The memoization strategy assumes each function exists on only one
20+
// prototype chain i.e. we use the function object for memoizing)
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// perhaps we can bookkeep on the prototype itself instead
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function $super(arrayOfArgs) {
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// since we are thunking a method call, performance is important here:
24+
// memoize all lookups, once memoized the fast path calls no other
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// functions
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//
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// find the caller (cannot be `strict` because of 'caller')
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var caller = $super.caller;
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// memoized 'name of method'
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var nom = caller.nom;
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// memoized next implementation prototype
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var _super = caller._super;
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if (!_super) {
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if (!nom) {
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nom = caller.nom = nameInThis.call(this, caller);
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}
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if (!nom) {
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console.warn('called super() on a method not installed declaratively (has no .nom property)');
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}
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// super prototype is either cached or we have to find it
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// by searching __proto__ (at the 'top')
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// invariant: because we cache _super on fn below, we never reach
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// here from inside a series of calls to super(), so it's ok to
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// start searching from the prototype of 'this' (at the 'top')
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// we must never memoize a null super for this reason
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_super = memoizeSuper(caller, nom, getPrototypeOf(this));
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}
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// our super function
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var fn = _super[nom];
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if (fn) {
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// memoize information so 'fn' can call 'super'
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if (!fn._super) {
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// must not memoize null, or we lose our invariant above
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memoizeSuper(fn, nom, _super);
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}
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// invoke the inherited method
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// if 'fn' is not function valued, this will throw
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return fn.apply(this, arrayOfArgs || []);
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}
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}
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function nameInThis(value) {
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var p = this.__proto__;
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while (p && p !== HTMLElement.prototype) {
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// TODO(sjmiles): getOwnPropertyNames is absurdly expensive
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var n$ = Object.getOwnPropertyNames(p);
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for (var i=0, l=n$.length, n; i<l && (n=n$[i]); i++) {
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var d = Object.getOwnPropertyDescriptor(p, n);
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if (typeof d.value === 'function' && d.value === value) {
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return n;
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}
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}
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p = p.__proto__;
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}
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}
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function memoizeSuper(method, name, proto) {
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// find and cache next prototype containing `name`
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// we need the prototype so we can do another lookup
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// from here
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var s = nextSuper(proto, name, method);
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if (s[name]) {
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// `s` is a prototype, the actual method is `s[name]`
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// tag super method with it's name for quicker lookups
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s[name].nom = name;
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}
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return method._super = s;
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}
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function nextSuper(proto, name, caller) {
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// look for an inherited prototype that implements name
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while (proto) {
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if ((proto[name] !== caller) && proto[name]) {
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return proto;
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}
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proto = getPrototypeOf(proto);
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}
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// must not return null, or we lose our invariant above
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// in this case, a super() call was invoked where no superclass
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// method exists
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// TODO(sjmiles): thow an exception?
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return Object;
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}
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// NOTE: In some platforms (IE10) the prototype chain is faked via
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// __proto__. Therefore, always get prototype via __proto__ instead of
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// the more standard Object.getPrototypeOf.
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function getPrototypeOf(prototype) {
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return prototype.__proto__;
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}
111+
112+
// utility function to precompute name tags for functions
113+
// in a (unchained) prototype
114+
function hintSuper(prototype) {
115+
// tag functions with their prototype name to optimize
116+
// super call invocations
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for (var n in prototype) {
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var pd = Object.getOwnPropertyDescriptor(prototype, n);
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if (pd && typeof pd.value === 'function') {
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pd.value.nom = n;
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}
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}
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}
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// exports
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scope.super = $super;
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})(Polymer);

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