bevy/release-content
Eagster 064e5e48b4
Remove entity placeholder from observers (#19440)
# Objective

`Entity::PLACEHOLDER` acts as a magic number that will *probably* never
really exist, but it certainly could. And, `Entity` has a niche, so the
only reason to use `PLACEHOLDER` is as an alternative to `MaybeUninit`
that trades safety risks for logic risks.

As a result, bevy has generally advised against using `PLACEHOLDER`, but
we still use if for a lot internally. This pr starts removing internal
uses of it, starting from observers.

## Solution

Change all trigger target related types from `Entity` to
`Option<Entity>`

Small migration guide to come.

## Testing

CI

## Future Work

This turned a lot of code from 

```rust
trigger.target()
```

to 

```rust
trigger.target().unwrap()
```

The extra panic is no worse than before; it's just earlier than
panicking after passing the placeholder to something else.

But this is kinda annoying. 

I would like to add a `TriggerMode` or something to `Event` that would
restrict what kinds of targets can be used for that event. Many events
like `Removed` etc, are always triggered with a target. We can make
those have a way to assume Some, etc. But I wanted to save that for a
future pr.
2025-06-09 19:37:56 +00:00
..
migration-guides Remove entity placeholder from observers (#19440) 2025-06-09 19:37:56 +00:00
release-notes Specialized UI transform (#16615) 2025-06-09 19:05:49 +00:00
migration_guides_template.md Make some changes to the migration guide recommendations (#18794) 2025-04-10 19:25:56 +00:00
migration_guides.md bevyengine.org -> bevy.org (#19503) 2025-06-05 23:09:28 +00:00
README.md Fixed broken link in release content README. (#19375) 2025-05-26 19:30:03 +00:00
release_notes_template.md
release_notes.md bevyengine.org -> bevy.org (#19503) 2025-06-05 23:09:28 +00:00

Release Content

This directory contains drafts of documentation for the current development cycle, which will be published to the website during the next release. You can find more information in the release notes and migration guides files.