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Merge pull request #5266 from Polymer/5262-kschaaf-legacy-undefined
[2.x] Add legacy-data-mixin as 1.x->2.x migration aide. Fixes #5262.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,171 @@ | ||
| <!-- | ||
| @license | ||
| Copyright (c) 2017 The Polymer Project Authors. All rights reserved. | ||
| This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt | ||
| The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt | ||
| The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt | ||
| Code distributed by Google as part of the polymer project is also | ||
| subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt | ||
| --> | ||
|
|
||
| <link rel="import" href="class.html"> | ||
| <link rel="import" href="../../polymer.html"> | ||
| <link rel="import" href="../utils/mixin.html"> | ||
| <link rel="import" href="../utils/templatize.html"> | ||
|
|
||
| <script> | ||
| (function() { | ||
| 'use strict'; | ||
|
|
||
| const UndefinedArgumentError = class extends Error { | ||
| constructor(message, arg) { | ||
| super(message); | ||
| this.arg = arg; | ||
| this.name = this.constructor.name; | ||
| // Affordances for ensuring instanceof works after babel ES5 compilation | ||
| // TODO(kschaaf): Remove after polymer CLI updates to newer Babel that | ||
| // sets the constructor/prototype correctly for subclassed builtins | ||
| this.constructor = UndefinedArgumentError; | ||
| this.__proto__ = UndefinedArgumentError.prototype; | ||
| } | ||
| }; | ||
|
|
||
| /** | ||
| * Wraps effect functions to catch `UndefinedArgumentError`s and warn. | ||
| * | ||
| * @param {Object=} effect Effect metadata object | ||
| * @param {Object=} fnName Name of user function, if known | ||
| * @return {?Object} Effect metadata object | ||
| */ | ||
| function wrapEffect(effect, fnName) { | ||
| if (effect && effect.fn) { | ||
| const fn = effect.fn; | ||
| effect.fn = function() { | ||
| try { | ||
| fn.apply(this, arguments); | ||
| } catch (e) { | ||
| if (e instanceof UndefinedArgumentError) { | ||
| console.warn(`Argument '${e.arg}'${fnName ?` for method '${fnName}'` : ''} was undefined. Ensure it has an undefined check.`); | ||
| } else { | ||
| throw e; | ||
| } | ||
| } | ||
| }; | ||
| } | ||
| return effect; | ||
| } | ||
|
|
||
| /** | ||
| * Mixin to selectively add back Polymer 1.x's `undefined` rules | ||
| * governing when observers & computing functions run based | ||
| * on all arguments being defined (reference https://www.polymer-project.org/1.0/docs/devguide/observers#multi-property-observers). | ||
| * | ||
| * When loaded, all legacy elements (defined with `Polymer({...})`) | ||
| * will have the mixin applied. The mixin only restores legacy data handling | ||
| * if `_legacyUndefinedCheck: true` is set on the element's prototype. | ||
| * | ||
| * This mixin is intended for use to help migration from Polymer 1.x to | ||
| * 2.x+ by allowing legacy code to work while identifying observers and | ||
| * computing functions that need undefined checks to work without | ||
| * the mixin in Polymer 2. | ||
| * | ||
| * @mixinFunction | ||
| * @polymer | ||
| * @summary Mixin to selectively add back Polymer 1.x's `undefined` rules | ||
| * governing when observers & computing functions run. | ||
| */ | ||
| Polymer.LegacyDataMixin = Polymer.dedupingMixin(superClass => { | ||
|
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||
| /** | ||
| * @polymer | ||
| * @mixinClass | ||
| * @implements {Polymer_LegacyDataMixin} | ||
| */ | ||
| class LegacyDataMixin extends superClass { | ||
| /** | ||
| * Overrides `Polyer.PropertyEffects` to add `undefined` argument | ||
| * checking to match Polymer 1.x style rules | ||
| * | ||
| * @param {!Array<!MethodArg>} args Array of argument metadata | ||
| * @param {string} path Property/path name that triggered the method effect | ||
| * @param {Object} props Bag of current property changes | ||
| * @return {Array<*>} Array of argument values | ||
| * @private | ||
| */ | ||
| _marshalArgs(args, path, props) { | ||
| const vals = super._marshalArgs(args, path, props); | ||
| // Per legacy data rules, single-property observers (whether in `properties` | ||
| // and in `observers`) are called regardless of whether their argument is | ||
| // undefined or not. Multi-property observers must have all arguments defined | ||
| if (this._legacyUndefinedCheck && vals.length > 1) { | ||
| for (let i=0; i<vals.length; i++) { | ||
| if (vals[i] === undefined) { | ||
| // Break out of effect's control flow; will be caught in | ||
| // wrapped property effect function below | ||
| const name = args[i].name; | ||
| throw new UndefinedArgumentError(`Argument '${name}' is undefined. Ensure it has an undefined check.`, name); | ||
| } | ||
| } | ||
| } | ||
| return vals; | ||
| } | ||
|
|
||
| /** | ||
| * Overrides `Polyer.PropertyEffects` to wrap effect functions to | ||
| * catch `UndefinedArgumentError`s and warn. | ||
| * | ||
| * @param {string} property Property that should trigger the effect | ||
| * @param {string} type Effect type, from this.PROPERTY_EFFECT_TYPES | ||
| * @param {Object=} effect Effect metadata object | ||
| * @return {void} | ||
| * @protected | ||
| */ | ||
| _addPropertyEffect(property, type, effect) { | ||
| return super._addPropertyEffect(property, type, | ||
| wrapEffect(effect, effect && effect.info && effect.info.methodName)); | ||
| } | ||
|
|
||
| /** | ||
| * Overrides `Polyer.PropertyEffects` to wrap effect functions to | ||
| * catch `UndefinedArgumentError`s and warn. | ||
| * | ||
| * @param {Object} templateInfo Template metadata to add effect to | ||
| * @param {string} prop Property that should trigger the effect | ||
| * @param {Object=} effect Effect metadata object | ||
| * @return {void} | ||
| * @protected | ||
| */ | ||
| static _addTemplatePropertyEffect(templateInfo, prop, effect) { | ||
| return super._addTemplatePropertyEffect(templateInfo, prop, wrapEffect(effect)); | ||
| } | ||
|
|
||
| } | ||
|
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| return LegacyDataMixin; | ||
|
|
||
| }); | ||
|
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| // LegacyDataMixin is applied to base class _before_ metaprogramming, to | ||
| // ensure override of _addPropertyEffect et.al. are used by metaprogramming | ||
| // performed in _finalizeClass | ||
| const Class = Polymer.Class; | ||
| Polymer.Class = (info, mixin) => Class(info, | ||
| superClass => mixin ? | ||
| mixin(Polymer.LegacyDataMixin(superClass)) : | ||
| Polymer.LegacyDataMixin(superClass) | ||
| ); | ||
|
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||
| // Apply LegacyDataMixin to Templatizer instances as well, and defer | ||
| // runtime switch to the root's host (_methodHost) | ||
| Polymer.Templatize.mixin = | ||
| Polymer.dedupingMixin(superClass => class extends Polymer.LegacyDataMixin(superClass) { | ||
| get _legacyUndefinedCheck() { | ||
| return this._methodHost && this._methodHost._legacyUndefinedCheck; | ||
| } | ||
| }); | ||
|
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| console.info('LegacyDataMixin will be applied to all legacy elements.\n' + | ||
| 'Set `_legacyUndefinedCheck: true` to enable.'); | ||
|
|
||
| })(); | ||
| </script> |
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