20127 2012-11-28 18:58:05 +0000 [Templates]: Template needs to disallow DOM hierarchy cycles which can result from template.contents 2013-02-08 17:53:53 +0000 1 1 1 Unclassified WebAppsWG HISTORICAL - Component Model unspecified PC All RESOLVED FIXED P2 normal --- 15476 1 rafaelw dglazkov adamk annevk dglazkov hsivonen travil tross wchen public-webapps-bugzilla oldest_to_newest 79028 0 rafaelw 2012-11-28 18:58:05 +0000 e.g. template.content.appendChild(template). Note that ShadowRoot has an nearly identical problem, we hopefully we can address both with the same solution. I propose the right behavior is DOM operation that would result in a cycle via template.content throw a DOM HIERARCHY exception the same way that it does now with parent/child cycles. 82101 1 rafaelw 2013-01-24 17:54:24 +0000 This has been implemented both for template element and also for ShadowRoot in WebKit. Note that I've made a non-normative comment about this in the template element spec. I suspect that maybe DOM needs to say something about this, but I'm not sure how to approach this. Anne, what's your feeling? 82102 2 rafaelw 2013-01-24 17:55:26 +0000 Note that last statement under the template element section: https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/templates/index.html#template-element 82139 3 annevk 2013-01-25 13:58:18 +0000 Lets keep this open until it's fixed then okay? So it seems like in addition to checking the inclusive ancestors as is already done by the pre-insert and replace algorithms, we also need to check the inclusive ancestors of the object the tree is associated with. Should we maybe introduce a new node that inherits from DocumentFragment that can carry that additional semantic as well as provide a pointer to the hosting element? 82159 4 adamk 2013-01-25 20:02:29 +0000 (In reply to comment #3) > Should we maybe introduce a new node that inherits from DocumentFragment > that can carry that additional semantic as well as provide a pointer to the > hosting element? When you say "provide a pointer" do you mean as part of its interface? The WebKit implementation of course does exactly what you describe (a DocumentFragment subclass, a pointer to the host <template>) but doesn't change at the WebIDL level. 82191 5 annevk 2013-01-26 08:42:57 +0000 Well the idea was a new interface as the functionality might be useful. But I guess for now I can add a concept to DocumentFragment named "host" and then add the appropriate checks to pre-insert and replace in case there's a DocumentFragment root which has a host defined. Would that work? 82242 6 rafaelw 2013-01-28 20:47:59 +0000 @Anne, I like your solution in comment 5. It seems like we should avoid exposing |host| as an IDL property until we have a clear use case. 82275 7 annevk 2013-01-29 12:36:42 +0000 If someone appends <template>.contents (or whatever that's called), that should just work right? 82349 8 adamk 2013-01-30 20:50:30 +0000 (In reply to comment #7) > If someone appends <template>.contents (or whatever that's called), that > should just work right? Yes, that'll simply remove everything from the content fragment and append it to wherever it got appended, as it works for any other fragment. But there's no way to "detach" the fragment from the <template> (its "host" property can't change). 82635 9 annevk 2013-02-06 17:40:47 +0000 https://github.com/whatwg/dom/commit/bc62c366536ace9fde6bbc9f0098d0f17a64aef1 http://dom.spec.whatwg.org/#concept-documentfragment-host You can now use this host concept in the <template> specification. 82653 10 rafaelw 2013-02-06 22:26:24 +0000 @Anne: The language in pre-insert doesn't look sufficient to me. I think you need to recursively traverse host boundaries. e.g. <div> <template> <div> <template> and append the outer div to the inner-most template.content. 82691 11 annevk 2013-02-07 12:37:49 +0000 https://github.com/whatwg/dom/commit/534a39839a8bb69b6cf57c7692fe16ead5b1bcb7 Thanks! 82716 12 rafaelw 2013-02-07 21:34:26 +0000 Ok. The spec now is clear that when the content document fragment is initialized, its host element is set to the template. https://dvcs.w3.org/hg/webcomponents/rev/1671f8bac2df I'm going to go ahead and close this and leave it to Anne to get the language correct in DOM about preventing hierarchy cycles. 82745 13 annevk 2013-02-08 10:09:41 +0000 Are you saying I did not fix it? I'm confused. 82771 14 rafaelw 2013-02-08 17:53:53 +0000 My bad. I didn't noticed that you had fixed it. Looks right to me now. Thanks!