# Objective
- Working with hierarchies in Bevy is far too tedious due to a lack of
helper functions.
- This is the first half of #15609.
## Solution
Extend
[`HierarchyQueryExt`](https://docs.rs/bevy/latest/bevy/hierarchy/trait.HierarchyQueryExt)
with the following methods:
- `parent`
- `children`
- `root_parent`
- `iter_leaves`
- `iter_siblings`
- `iter_descendants_depth_first`
I've opted to make both `iter_leaves` and `iter_siblings` collect the
list of matching Entities for now, rather that operate by reference like
the existing `iter_descendants`. This was simpler, and in the case of
`iter_siblings` especially, the number of matching entities is likely to
be much smaller.
I've kept the generics in the type signature however, so we can go back
and optimize that freely without a breaking change whenever we want.
## Testing
I've added some basic testing, but they're currently failing. If you'd
like to help, I'd welcome suggestions or a PR to my PR over the weekend
<3
---------
Co-authored-by: Viktor Gustavsson <villor94@gmail.com>
Co-authored-by: poopy <gonesbird@gmail.com>
Co-authored-by: Christian Hughes <9044780+ItsDoot@users.noreply.github.com>
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