28849 2015-06-24 23:39:41 +0000 Cloning steps for ES Map/Set should copy [[MapData]]/[[SetData]] list before recursing 2015-09-01 03:54:54 +0000 1 1 1 Unclassified WHATWG HTML unspecified Other other RESOLVED MOVED https://html.spec.whatwg.org/#safe-passing-of-structured-data P3 normal Unsorted 1 contributor ian adamk annevk mike contributor oldest_to_newest 121468 0 contributor 2015-06-24 23:39:41 +0000 Specification: https://html.spec.whatwg.org/multipage/infrastructure.html Multipage: https://html.spec.whatwg.org/multipage/#safe-passing-of-structured-data Complete: https://html.spec.whatwg.org/#safe-passing-of-structured-data Referrer: https://html.spec.whatwg.org/multipage/ Comment: Cloning steps for ES Map/Set should copy [[MapData]]/[[SetData]] list before recursing Posted from: 72.14.229.81 User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/43.0.2357.130 Safari/537.36 121469 1 adamk 2015-06-24 23:47:06 +0000 The spec as currently-written says: "1. Let source be the List that is the value of input's [[SetData]] internal slot, if any." Consider the following code: var set = new Set; var mutator = { get val() { set.add('mutator was here') } }; set.add(mutator); onmessage = function(e) { console.log(e.data.size); }; postMessage(set, '*') What should be printed to the console? In Firefox, this example prints '1' (Chrome will print 1, soon, once it supports cloning Maps and Sets). But the spec suggests that it should print '2', since step 7.3.1 invokes the clone algorithm on |mutator| and thus adds another item to set's [[SetData]] List. I'd recommend that the spec change to explicitly make a copy of [[SetData]] (and [[MapData]], for maps) before attempting to clone anything contained in those lists. This will match the existing implementation, and should be easier to implement in general. 122875 2 annevk 2015-08-28 17:01:33 +0000 Adam, would you be willing to provide a pull request for https://github.com/whatwg/html? 122934 3 adamk 2015-08-31 21:50:22 +0000 (In reply to Anne from comment #2) > Adam, would you be willing to provide a pull request for > https://github.com/whatwg/html? https://github.com/whatwg/html/pull/64 122935 4 annevk 2015-09-01 03:54:54 +0000 Thank you!