Re: [whatwg/webidl] Introduce a "detachable" algorithm for BufferSource (PR #1419)

@inexorabletash commented on this pull request.



> @@ -9054,6 +9054,21 @@ a reference to the same object that the IDL value represents.
     1.  Return [$IsDetachedBuffer$](|jsArrayBuffer|).
 </div>
 
+<div algorithm>
+    A [=buffer source type=] instance |bufferSource| is
+    <dfn for="BufferSource" export>detachable</dfn> if the following steps return true:
+
+    1.  Let |jsArrayBuffer| be the result of [=converted to a JavaScript value|converting=]
+        |bufferSource| to a JavaScript value.
+    1.  If |jsArrayBuffer| has a \[[ViewedArrayBuffer]] internal slot, then set |jsArrayBuffer| to
+        |jsArrayBuffer|.\[[ViewedArrayBuffer]].
+    1.  If [$IsSharedArrayBuffer$](|jsArrayBuffer|) is true, then return false.
+    1.  If [$IsDetachedBuffer$](|jsArrayBuffer|) is true, then return false.

Hopefully I'm not misunderstanding your question. The use case is over at https://webmachinelearning.github.io/webnn/#mlnamedarraybufferviews-transfer

Shorter version for explanatory purposes:

1. For each _buffer_ of _buffers_:
    1. If _buffer_ is not **detachable**, then throw a TypeError.
1. For each _buffer_ of _buffers_:
    1. Let _xfer_ be the result of [transferring](https://webidl.spec.whatwg.org/#arraybuffer-transfer) _buffer_'s underlying buffer.

The "IsDetachedBuffer" check is to ensure that [transferring](https://webidl.spec.whatwg.org/#arraybuffer-transfer) wouldn't assert ("_Assert: IsDetachedBuffer(jsArrayBuffer) is false"_).

This could alternately be done by the caller, e.g.:

1. For each _buffer_ of _buffers_:
    1. If _buffer_ has a [[ViewedArrayBuffer]] internal slot, then set _buffer_ to _buffer_.[[ViewedArrayBuffer]].
    1. If [IsDetachedBuffer](https://tc39.es/ecma262/multipage/structured-data.html#sec-isdetachedbuffer)(_buffer_) is true, then throw a TypeError.
    1. If _buffer_ is not **detachable**, then throw a TypeError.
1. For each _buffer_ of _buffers_:
    1. Let _xfer_ be the result of [transferring](https://webidl.spec.whatwg.org/#arraybuffer-transfer) _buffer_'s underlying buffer.

... but it seems we'd want to keep this logic together in WebIDL. Would it be clearer if we named the new algorithm **transferable** instead?

(But maybe I'm answering the wrong question?)

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