Implement undefined-like exotic objects #673
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@@ -39904,6 +39904,60 @@ <h1>Initializers in ForIn Statement Heads</h1> | |
| 1. Return ? ForIn/OfBodyEvaluation(|BindingIdentifier|, |Statement|, _keyResult_, ~enumerate~, ~varBinding~, _labelSet_). | ||
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| <emu-annex id="sec-ishtmldda-internal-slot"> | ||
| <h1>The [[isHTMLDDA]] Internal Slot</h1> | ||
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There was a problem hiding this comment. Uppercase to match other internal slot names? |
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| <p>An <dfn>[[isHTMLDDA]] internal slot</dfn> may exist on implementation-defined exotic objects. Objects with an [[isHTMLDDA]] intenral slot behave like undefined in the <emu-xref href="#sec-toboolean">ToBoolean</emu-xref> and <emu-xref href="#sec-abstract-equality-comparison">Abstract Equality Comparison</emu-xref> abstract operations and when used as an operand for the <emu-xref href="#sec-typeof-operator">typeof operator</emu-xref>.</p> | ||
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It looks like
This isn't quite right, as HTML will define one with overridden internal methods. Not sure what the right phrasing is... "By default, ... (but other specifications may create HTML document dot all exotic objects with overridden internal methods)"? There was a problem hiding this comment. Maybe one way to do this would be to state somehow that any object (well, one precise object) can be "marked" as a HTML document dot all exotic object, not that it "is" a HTML dot all exotic object. That way it could be a "legacy platform exotic object" (= using various internal methods defined by Web IDL) plus be marked as a HTML document dot all exotic object, at the same time. There was a problem hiding this comment. Typo "intenrel" typeof still not codeified. Actually just using title="" attribute might work better? For most of these xrefs? Maybe even it's not required at all for ToBoolean? There was a problem hiding this comment. It should be “object(s)” rather than “exotic object(s)” (here and everywhere below). Although the behaviour described in this section is very “exotic” according the common meaning of that word, it does not make an exotic object in the sense of the definition given by the spec. There was a problem hiding this comment. I think it's still fair, since There was a problem hiding this comment. I think @claudepache is right - the object may be exotic depending on host choices, but it's confusing to say its exotic when it doesn't define anything exotic. Might trigger someone to go sleuthing for hours trying to find the missing exoticness. I'll fix it. |
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| <emu-note> | ||
| <p>Objects with an [[isHTMLDDA]] internal slot are never created by this specification. However, the <a href="https://html.spec.whatwg.org/multipage/obsolete.html#dom-document-all"><code>document.all</code> object</a> in web browsers is a host-created exotic object with this slot that exists for web compatibility purposes. There are no other known examples of this type of object and implementations should not create any with the exception of `document.all`.</p> | ||
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There was a problem hiding this comment. Maybe add a requirement on hosts? s/this type of object/and none must be introduced/ There was a problem hiding this comment. This was discussed somewhat, I think there was resistance to "overreach", but I'm definitely fine with the note saying something to this effect. There was a problem hiding this comment. Wouldn't it be better to point to There was a problem hiding this comment. I think document.all is better. There's nothing special about HTMLAllCollection itself, really. Its instances are the weird ones. And a good way of collectively referring to all such instances is probably "document.all". There was a problem hiding this comment. @annevk I only went with "should" because this is a note and it seems odd to use strong language in a non-normative section. |
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| <emu-annex id="sec-html-document-dot-all-exotic-object-to-boolean"> | ||
| <h1>Changes to ToBoolean</h1> | ||
| <p>The result column in <emu-xref href="#table-10"></emu-xref> for an argument type of Object is replaced with the following algorithm:</p> | ||
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| 1. If _argument_ has an [[isHTMLDDA]] internal slot, return *false*. | ||
| 1. Return *true*. | ||
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There was a problem hiding this comment. In this algorithm, switch “true” and “false”. |
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| <emu-annex id="sec-html-document-dot-all-exotic-object-aec"> | ||
| <h1>Changes to Abstract Equality Comparison</h1> | ||
| <p>The following steps are inserted after step 3 of the <emu-xref href="#sec-abstract-equality-comparison">Abstract Equality Comparison</emu-xref> algorithm:</p> | ||
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There was a problem hiding this comment. Consider labeling steps and referring to them by labels, as this is kind of fragile. However, it is how things have worked so far, so no need to fix if you'd rather keep as-is. There was a problem hiding this comment. Step labels sure would be nice, but I'll leave this as-is for now. |
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There was a problem hiding this comment. hmm I thought this did something but it doesn't. Guess I'll delete it. |
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| 1. If _x_ has an [[isHTMLDDA]] internal slot and _y_ is either *null* or *undefined*, return *true*. | ||
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There was a problem hiding this comment. HTML document dot all exotic object |
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| 1. If _x_ is either *null* or *undefined* and _y_ has an [[isHTMLDDA]] internal slot, return *true*. | ||
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| <emu-annex id="sec-html-document-dot-all-exotic-object-typeof"> | ||
| <h1>Changes to the `typeof` operator</h1> | ||
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| <p>The following table entry is inserted into <emu-xref href="#table-35"></emu-xref> immediately preceeding the entry for "Object (implements [[Call]])":</p> | ||
| <emu-table> | ||
| <emu-caption> | ||
| Additional <emu-xref href="#sec-typeof-operator">`typeof`</emu-xref> Operator Results | ||
| </emu-caption> | ||
| <table> | ||
| <tr> | ||
| <th> | ||
| Type of _val_ | ||
| </th> | ||
| <th> | ||
| Result | ||
| </th> | ||
| </tr> | ||
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There was a problem hiding this comment. xref? I guess we're already in the section due to annex B funtimes, so maybe it doesn't need to be. |
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| <tr> | ||
| <td> | ||
| Object (has an [[isHTMLDDA]] internal slot) | ||
| </td> | ||
| <td> | ||
| `"undefined"` | ||
| </td> | ||
| </tr> | ||
| </table> | ||
| </emu-table> | ||
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"Document Dot All", or
document.all? I feel like we may have lost something in the minutes from the TC39 meeting :).Either way is fine, although the latter is slightly less ugly.
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HA, maybe! I just assumed it was a deliberately bad editorial choice to underscore the badness of the thing being specified.