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This spec draft is in line with issue mikewest#2 with @domenic's suggestion for where the brand check function should go.
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| <!DOCTYPE html> | ||
| <meta charset="utf-8"> | ||
| <pre class="metadata"> | ||
| title: Template Literal Tracking | ||
| status: proposal | ||
| stage: 1 | ||
| location: https://littledan.github.io/tc39-proposal-literals/ | ||
| copyright: false | ||
| contributors: Mike West, Adam Klein, Daniel Ehrenberg | ||
| </pre> | ||
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| <emu-clause id="sec-introduction"> | ||
| <h1>Introduction</h1> | ||
| <p>This proposal describes a mechanism for tracking literal strings in APIs by providing a mechanism that temlate tags can use to ensure that they are being called with actual literals. See <a href="https://github.com/mikewest/tc39-proposal-literals">the explainer</a> for more context.</p> | ||
| <p>This spec draft describes a strawman by Daniel Ehrenberg (not one of the champions) for how the semantic details could be worked out in line with <a href="https://github.com/mikewest/tc39-proposal-literals/issues/2">Issue #2</a>. It's intended as a basis for discussion, not in any way authoritative. In this draft, a new function, Array.isTemplateLiteral is provided to check the brand of template objects which resulted from literal ECMAScript code. With this design, a template literal which was included in an `eval` call will be tagged as a literal.</p> | ||
| </emu-clause> | ||
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| <!-- es6num="12.2.9.3" --> | ||
| <emu-clause id="sec-gettemplateobject" aoid="GetTemplateObject"> | ||
| <h1>Runtime Semantics: GetTemplateObject ( _templateLiteral_ )</h1> | ||
| <p>The abstract operation GetTemplateObject is called with a Parse Node, _templateLiteral_, as an argument. It performs the following steps:</p> | ||
| <emu-alg> | ||
| 1. Let _rawStrings_ be TemplateStrings of _templateLiteral_ with argument *true*. | ||
| 1. Let _realm_ be the current Realm Record. | ||
| 1. Let _templateRegistry_ be _realm_.[[TemplateMap]]. | ||
| 1. For each element _e_ of _templateRegistry_, do | ||
| 1. If _e_.[[Strings]] and _rawStrings_ contain the same values in the same order, then | ||
| 1. Return _e_.[[Array]]. | ||
| 1. Let _cookedStrings_ be TemplateStrings of _templateLiteral_ with argument *false*. | ||
| 1. Let _count_ be the number of elements in the List _cookedStrings_. | ||
| 1. Assert: _count_ ≤ 2<sup>32</sup>-1. | ||
| 1. Let _template_ be ! ArrayCreate(_count_<ins>, %ArrayPrototype%, « [[TemplateLiteral]] »</ins>). | ||
| 1. Let _rawObj_ be ! ArrayCreate(_count_). | ||
| 1. Let _index_ be 0. | ||
| 1. Repeat, while _index_ < _count_ | ||
| 1. Let _prop_ be ! ToString(_index_). | ||
| 1. Let _cookedValue_ be the String value _cookedStrings_[_index_]. | ||
| 1. Call _template_.[[DefineOwnProperty]](_prop_, PropertyDescriptor{[[Value]]: _cookedValue_, [[Writable]]: *false*, [[Enumerable]]: *true*, [[Configurable]]: *false*}). | ||
| 1. Let _rawValue_ be the String value _rawStrings_[_index_]. | ||
| 1. Call _rawObj_.[[DefineOwnProperty]](_prop_, PropertyDescriptor{[[Value]]: _rawValue_, [[Writable]]: *false*, [[Enumerable]]: *true*, [[Configurable]]: *false*}). | ||
| 1. Let _index_ be _index_+1. | ||
| 1. Perform SetIntegrityLevel(_rawObj_, `"frozen"`). | ||
| 1. Call _template_.[[DefineOwnProperty]](`"raw"`, PropertyDescriptor{[[Value]]: _rawObj_, [[Writable]]: *false*, [[Enumerable]]: *false*, [[Configurable]]: *false*}). | ||
| 1. Perform SetIntegrityLevel(_template_, `"frozen"`). | ||
| 1. Append the Record{[[Strings]]: _rawStrings_, [[Array]]: _template_} to _templateRegistry_. | ||
| 1. Return _template_. | ||
| </emu-alg> | ||
| <emu-note> | ||
| <p>The creation of a template object cannot result in an abrupt completion.</p> | ||
| </emu-note> | ||
| <emu-note> | ||
| <p>Each |TemplateLiteral| in the program code of a realm is associated with a unique template object that is used in the evaluation of tagged Templates (<emu-xref href="#sec-template-literals-runtime-semantics-evaluation"></emu-xref>). The template objects are frozen and the same template object is used each time a specific tagged Template is evaluated. Whether template objects are created lazily upon first evaluation of the |TemplateLiteral| or eagerly prior to first evaluation is an implementation choice that is not observable to ECMAScript code.</p> | ||
| </emu-note> | ||
| <emu-note> | ||
| <p>Future editions of this specification may define additional non-enumerable properties of template objects.</p> | ||
| </emu-note> | ||
| </emu-clause> | ||
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| <!-- es6num="9.4.2.2" --> | ||
| <emu-clause id="sec-arraycreate" aoid="ArrayCreate"> | ||
| <h1>ArrayCreate ( _length_ [ , _proto_ [ , _internalSlotsList_ ] ] )</h1> | ||
| <p>The abstract operation ArrayCreate with argument _length_ (either 0 or a positive integer) and optional argument _proto_ is used to specify the creation of new Array exotic objects. It performs the following steps:</p> | ||
| <emu-alg> | ||
| 1. Assert: _length_ is an integer Number ≥ 0. | ||
| 1. If _length_ is *-0*, set _length_ to *+0*. | ||
| 1. If _length_>2<sup>32</sup>-1, throw a *RangeError* exception. | ||
| 1. If _proto_ is not present, set _proto_ to the intrinsic object %ArrayPrototype%. | ||
| 1. <ins>If _internalSlotsList_ is not present, set _internalSlotsList_ to a new empty List.</ins> | ||
| 1. Let _A_ be a newly created Array exotic object <ins>with an internal slot for each name in _internalSlotsList_</ins>. | ||
| 1. Set _A_'s essential internal methods except for [[DefineOwnProperty]] to the default ordinary object definitions specified in <emu-xref href="#sec-ordinary-object-internal-methods-and-internal-slots"></emu-xref>. | ||
| 1. Set _A_.[[DefineOwnProperty]] as specified in <emu-xref href="#sec-array-exotic-objects-defineownproperty-p-desc"></emu-xref>. | ||
| 1. Set _A_.[[Prototype]] to _proto_. | ||
| 1. Set _A_.[[Extensible]] to *true*. | ||
| 1. Perform ! OrdinaryDefineOwnProperty(_A_, `"length"`, PropertyDescriptor{[[Value]]: _length_, [[Writable]]: *true*, [[Enumerable]]: *false*, [[Configurable]]: *false*}). | ||
| 1. Return _A_. | ||
| </emu-alg> | ||
| </emu-clause> | ||
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| <!-- es6num="22.1.2" --> | ||
| <emu-clause id="sec-properties-of-the-array-constructor"> | ||
| <h1>Properties of the Array Constructor</h1> | ||
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| <!-- es6num="22.1.2.1" --> | ||
| <emu-clause id="sec-array.isTemplateLiteral"> | ||
| <h1>Array.isTemplateLiteral ( _array_ )</h1> | ||
| <p>When the `isTemplateLiteral` method is called with argument _array_, the following steps are taken:</p> | ||
| <emu-alg> | ||
| 1. If _array_ has a [[TemplateLiteral]] internal slot, return *true*. | ||
| 1. Otherwise, return *false*. | ||
| </emu-alg> | ||
| </emu-clause> | ||
| </emu-clause> |