Fix fragmentInstance#compareDocumentPosition nesting and portal cases #34069
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Found a couple of bugs when integrating this API into fabric. 1) Basic checks of nested host instances were inaccurate. For example, checking the first child of the first child of the Fragment would not return CONTAINED_BY. 2) The DOM positioning relied on the assumption that the first and last top-level children were in the same order as the Fiber tree. I added additional checks against the parent's position in the DOM, and special cased a portaled Fragment by getting its DOM parent from the child instance, rather than taking the instance from the Fiber return. This should be accurate in more cases. Though its still a guess and I'm not sure yet I've covered every variation of this. Portals are hard to deal with and we may end up having to push more results towards IMPLEMENTATION_SPECIFIC if accuracy is an issue.
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…#34069) Found a couple of issues while integrating FragmentInstance#compareDocumentPosition into Fabric. 1. Basic checks of nested host instances were inaccurate. For example, checking the first child of the first child of the Fragment would not return CONTAINED_BY. 2. Then fixing that logic exposed issues with Portals. The DOM positioning relied on the assumption that the first and last top-level children were in the same order as the Fiber tree. I added additional checks against the parent's position in the DOM, and special cased a portaled Fragment by getting its DOM parent from the child instance, rather than taking the instance from the Fiber return. This should be accurate in more cases. Though its still a guess and I'm not sure yet I've covered every variation of this. Portals are hard to deal with and we may end up having to push more results towards IMPLEMENTATION_SPECIFIC if accuracy is an issue. DiffTrain build for [a96a0f3](a96a0f3)
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…#34069) Found a couple of issues while integrating FragmentInstance#compareDocumentPosition into Fabric. 1. Basic checks of nested host instances were inaccurate. For example, checking the first child of the first child of the Fragment would not return CONTAINED_BY. 2. Then fixing that logic exposed issues with Portals. The DOM positioning relied on the assumption that the first and last top-level children were in the same order as the Fiber tree. I added additional checks against the parent's position in the DOM, and special cased a portaled Fragment by getting its DOM parent from the child instance, rather than taking the instance from the Fiber return. This should be accurate in more cases. Though its still a guess and I'm not sure yet I've covered every variation of this. Portals are hard to deal with and we may end up having to push more results towards IMPLEMENTATION_SPECIFIC if accuracy is an issue. DiffTrain build for [a96a0f3](a96a0f3)
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Stacked on #34069 Same basic semantics as the react-dom for determining document position of a Fragment compared to a given node. It's simpler here because we don't have to deal with inserted nodes or portals. So we can skip a bunch of the validation logic. The logic for handling empty fragments is the same so I've split out `compareDocumentPositionForEmptyFragment` into a shared module. There doesn't seem to be a great place to put shared DOM logic between Fabric and DOM configs at the moment. There may be more of this coming as we add more and more DOM APIs to RN. For testing I've written Fantom tests internally which pass the basic cases on this build. The renderer we have configured for Fabric tests in the repo doesn't support the Element APIs we need like `compareDocumentPosition`.
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Stacked on #34069 Same basic semantics as the react-dom for determining document position of a Fragment compared to a given node. It's simpler here because we don't have to deal with inserted nodes or portals. So we can skip a bunch of the validation logic. The logic for handling empty fragments is the same so I've split out `compareDocumentPositionForEmptyFragment` into a shared module. There doesn't seem to be a great place to put shared DOM logic between Fabric and DOM configs at the moment. There may be more of this coming as we add more and more DOM APIs to RN. For testing I've written Fantom tests internally which pass the basic cases on this build. The renderer we have configured for Fabric tests in the repo doesn't support the Element APIs we need like `compareDocumentPosition`. DiffTrain build for [45a6532](45a6532)
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Aug 15, 2025
Stacked on #34069 Same basic semantics as the react-dom for determining document position of a Fragment compared to a given node. It's simpler here because we don't have to deal with inserted nodes or portals. So we can skip a bunch of the validation logic. The logic for handling empty fragments is the same so I've split out `compareDocumentPositionForEmptyFragment` into a shared module. There doesn't seem to be a great place to put shared DOM logic between Fabric and DOM configs at the moment. There may be more of this coming as we add more and more DOM APIs to RN. For testing I've written Fantom tests internally which pass the basic cases on this build. The renderer we have configured for Fabric tests in the repo doesn't support the Element APIs we need like `compareDocumentPosition`. DiffTrain build for [45a6532](45a6532)
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Found a couple of issues while integrating FragmentInstance#compareDocumentPosition into Fabric.