protogenes commented on PR #962:
URL: https://github.com/apache/jackrabbit-oak/pull/962#issuecomment-5726818166
Despite this being an old, merged topic, here still seems like the best
place for discussion.
I encountered a corner case that works with `ClassicMove` but not with
`NeoMove`:
If you indirectly move a tree to a path below its original location `/x ->
/x/a`, all `Tree` references to descendants become invalid.
```java
Tree xx = root.getTree("/x/xx");
root.move("/x", "/a");
// workaround: xx.getPath();
root.getTree("/").addChild("x");
root.move("/a", "/x/a");
assertEquals("/x/a/xx", xx.getPath()); // fails as path is "/x/a/a/xx" with
NeoMove
```
Looking at `org.apache.jackrabbit.oak.core.MutableTree#applyPendingMoves`
the moves are applied multiple times to a path:
1. moves are applied to the parent tree
2. `NeoMove.apply` constructs the most recent path and then
3. applies the same moves again, if the paths overlap as above
The easy solution is to store the path instead of constructing it from the
parent which was already rewritten.
The stored path matches the state of pendingMoves at all times and can be
rewritten directly.
Alternatively one could restore the path matching the pendingMoves by
reverse-rewriting the parent path, requiring a weak back reference in `NeoMove`
and effectively doubling the rewrite operations.
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