# Objective
Improve querying ergonomics around collections and iterators of entities.
Example how queries over Children might be done currently.
```rust
fn system(foo_query: Query<(&Foo, &Children)>, bar_query: Query<(&Bar, &Children)>) {
for (foo, children) in &foo_query {
for child in children.iter() {
if let Ok((bar, children)) = bar_query.get(*child) {
for child in children.iter() {
if let Ok((foo, children)) = foo_query.get(*child) {
// D:
}
}
}
}
}
}
```
Answers #4868
Partially addresses #4864Fixes#1470
## Solution
Based on the great work by @deontologician in #2563
Added `iter_many` and `many_for_each_mut` to `Query`.
These take a list of entities (Anything that implements `IntoIterator<Item: Borrow<Entity>>`).
`iter_many` returns a `QueryManyIter` iterator over immutable results of a query (mutable data will be cast to an immutable form).
`many_for_each_mut` calls a closure for every result of the query, ensuring not aliased mutability.
This iterator goes over the list of entities in order and returns the result from the query for it. Skipping over any entities that don't match the query.
Also added `unsafe fn iter_many_unsafe`.
### Examples
```rust
#[derive(Component)]
struct Counter {
value: i32
}
#[derive(Component)]
struct Friends {
list: Vec<Entity>,
}
fn system(
friends_query: Query<&Friends>,
mut counter_query: Query<&mut Counter>,
) {
for friends in &friends_query {
for counter in counter_query.iter_many(&friends.list) {
println!("Friend's counter: {:?}", counter.value);
}
counter_query.many_for_each_mut(&friends.list, |mut counter| {
counter.value += 1;
println!("Friend's counter: {:?}", counter.value);
});
}
}
```
Here's how example in the Objective section can be written with this PR.
```rust
fn system(foo_query: Query<(&Foo, &Children)>, bar_query: Query<(&Bar, &Children)>) {
for (foo, children) in &foo_query {
for (bar, children) in bar_query.iter_many(children) {
for (foo, children) in foo_query.iter_many(children) {
// :D
}
}
}
}
```
## Additional changes
Implemented `IntoIterator` for `&Children` because why not.
## Todo
- Bikeshed!
Co-authored-by: deontologician <deontologician@gmail.com>
Co-authored-by: devil-ira <justthecooldude@gmail.com>
Required for https://github.com/bevyengine/bevy/pull/4402.
# Objective
- derived `SystemParam` implementations were never `ReadOnlySystemParamFetch`
- We want them to be, e.g. for `EventReader`
## Solution
- If possible, 'forward' the impl of `ReadOnlySystemParamFetch`.
The only tests we had for `derive(WorldQuery)` checked that the derive doesnt panic/emit a `compiler_error!`. This PR adds tests that actually assert the returned values of a query using the derived `WorldQuery` impl. Also adds a compile fail test to check that we correctly error on read only world queries containing mutable world queries.
Fixes#3408#3001 also solves this but I dont see it getting merged any time soon so...
# Objective
make bevy ecs a lil bit less unsound
## Solution
make `EntityMut::get_component_mut` return borrows from self instead of `'w`
# Objective
- std's new APIs do the same thing as `Query::get_multiple_mut`, but are called `get_many`: https://github.com/rust-lang/rust/pull/83608
## Solution
- Find and replace `get_multiple` with `get_many`
# Objective
- The inability to have multiple active mutable borrows into a query is a common source of borrow-checker pain for users.
- This is a pointless restriction if and only if we can guarantee that the entities they are accessing are unique.
- This could already by bypassed with get_unchecked, but that is an extremely unsafe API.
- Closes https://github.com/bevyengine/bevy/issues/2042.
## Solution
- Add `get_multiple`, `get_multiple_mut` and their unchecked equivalents (`multiple` and `multiple_mut`) to `Query` and `QueryState`.
- Improve the `QueryEntityError` type to provide more useful error information.
## Changelog
- Added `get_multiple`, `get_multiple_mut` and their unchecked equivalents (`multiple` and `multiple_mut`) to Query and QueryState.
## Migration Guide
- The `QueryEntityError` enum now has a `AliasedMutability variant, and returns the offending entity.
## Context
This is a fresh attempt at #3333; rebasing was behaving very badly and it was important to rebase on top of the recent query soundness fixes. Many thanks to all the reviewers in that thread, especially @BoxyUwU for the help with lifetimes.
## To-do
- [x] Add compile fail tests
- [x] Successfully deduplicate code
- [x] Decide what to do about failing doc tests
- [x] Get some reviews for lifetime soundness
# Objective
Add a system parameter `ParamSet` to be used as container for conflicting parameters.
## Solution
Added two methods to the SystemParamState trait, which gives the access used by the parameter. Did the implementation. Added some convenience methods to FilteredAccessSet. Changed `get_conflicts` to return every conflicting component instead of breaking on the first conflicting `FilteredAccess`.
Co-authored-by: bilsen <40690317+bilsen@users.noreply.github.com>
# Objective
- New clippy lints with rust 1.57 are failing
## Solution
- Fixed clippy lints following suggestions
- I ignored clippy in old renderer because there was many and it will be removed soon
A sample implementation of how to have `iter()` work on mutable queries without breaking aliasing rules.
# Objective
- Fixes#753
## Solution
- Added a ReadOnlyFetch to WorldQuery that is the `&T` version of `&mut T` that is used to specify the return type for read only operations like `iter()`.
- ~~As the comment suggests specifying the bound doesn't work due to restrictions on defining recursive implementations (like `Or`). However bounds on the functions are fine~~ Never mind I misread how `Or` was constructed, bounds now exist.
- Note that the only mutable one has a new `Fetch` for readonly as the `State` has to be the same for any of this to work
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
# Objective
bevy_ecs has several compile_fail tests that assert lifetime safety. In the past, these tests have been green for the wrong reasons (see e.g. #2984). This PR makes sure, that they will fail if the compiler error changes.
## Solution
Use [trybuild](https://crates.io/crates/trybuild) to assert the compiler errors.
The UI tests are in a separate crate that is not part of the Bevy workspace. This is to ensure that they do not break Bevy's crater builds. The tests get executed by the CI workflow on the stable toolchain.
