Fix GH-11500: Namespace reuse in createElementNS() generates wrong output #11528
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… output When you construct a DOM tree containing subtrees which are constructed top-down, this won't remove the redundant namespaces. That's because the following conditions hold: 1) The namespace are reused from the doc->oldNs list. 2) Therefore during reconciliation no nsDef field is set, so no redundant namespaces are removed by our reconciliation code. Furthermore, it would only be fixed up automatically if the tree wasn't added in bottom-up way, or if it had been constructed bottom-up from the start. Fix it by setting a flag to remove redundant namespaces in the libxml2 reconciliation call. Since removing redundant namespaces may have a performance cost, we only do this after performing a simple check.
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Forgot to split the commits up in a before and after. Here's the diff as a gist, the removed lines are the old behaviour and the green lines the new behaviour https://gist.github.com/nielsdos/40d26d1df9339ab974f027f8c8ff82a5 |
Girgias
approved these changes
Jun 26, 2023
| @@ -1494,7 +1494,8 @@ static void dom_libxml_reconcile_ensure_namespaces_are_declared(xmlNodePtr nodep | |||
| * Although libxml2 currently does not use this for the reconciliation, it still | |||
| * makes sense to do this just in case libxml2's internal change in the future. */ | |||
| xmlDOMWrapCtxt dummy_ctxt = {0}; | |||
| xmlDOMWrapReconcileNamespaces(&dummy_ctxt, nodep, /* options */ 0); | |||
| bool remove_redundant = nodep->nsDef == NULL && nodep->ns != NULL; | |||
| xmlDOMWrapReconcileNamespaces(&dummy_ctxt, nodep, /* options */ remove_redundant ? (1 << 0) : 0); | |||
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Should the (1 << 0) be exposed as a constant somewhere?
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Sadly libxml2 doesn't have a define for this. I can make my own define (but with a PHP_LIBXML2_ prefix to prevent name collisions). I'll do that in the merge.
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When you construct a DOM tree containing subtrees which are constructed top-down, this won't remove the redundant namespaces. That's because the following conditions hold:
namespaces are removed by our reconciliation code.
Furthermore, it would only be fixed up automatically if the tree wasn't added in bottom-up way, or if it had been constructed bottom-up from the start.
Fix it by setting a flag to remove redundant namespaces in the libxml2 reconciliation call.
Since removing redundant namespaces may have a performance cost, we only do this after performing a simple check.
Closes GH-11500