[Merged by Bors] - remove QF generics from all `Query/State` methods and types#5170

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BoxyUwU:remove_QF_generics

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BoxyUwU commented Jul 1, 2022 •

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Objective

remove QF generics from a bunch of types and methods on query related items. this has a few benefits:

simplifies type signatures fn iter(&self) -> QueryIter<'_, 's, Q::ReadOnly, F::ReadOnly> is (imo) conceptually simpler than fn iter(&self) -> QueryIter<'_, 's, Q, ROQueryFetch<'_, Q>, F>
Fetch is mostly an implementation detail but previously we had to expose it on every iter get etc method
Allows us to potentially in the future simplify the WorldQuery trait hierarchy by removing the Fetch trait

Solution

remove the QF generic and add a way to (unsafely) turn &QueryState<Q1, F1> into &QueryState<Q2, F2>

Changelog/Migration Guide

The QF generic was removed from various Query iterator types and some methods, you should update your code to use the type of the corresponding worldquery of the fetch type that was being used, or call as_readonly/as_nop to convert a querystate to the appropriate type. For example:
.get_single_unchecked_manual::<ROQueryFetch<Q>>(..) -> .as_readonly().get_single_unchecked_manual(..)
my_field: QueryIter<'w, 's, Q, ROQueryFetch<'w, Q>, F> -> my_field: QueryIter<'w, 's, Q::ReadOnly, F::ReadOnly>

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July 1, 2022 19:04

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I really like how this cleans up this area, but there are some pressing questions about how as_whatever works.

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crates/bevy_ecs/src/query/state.rs

                   pub fn iter_combinations<'w, 's, const K: usize>(
                       &'s mut self,
                       world: &'w World,
-                  ) -> QueryCombinationIter<'w, 's, Q, F, K> {

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BoxyUwU Jul 1, 2022

this is a soundness fix, but it would be possible to make a much smaller PR solely fixing this soundness bug if we wanted (I would rather just do this PR though)

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alice-i-cecile commented Jul 1, 2022

I like this a lot. It simplifies the trait soup substantially and will make contributing simple things (like Query methods) much less painful.

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crates/bevy_ecs/src/query/state.rs

+                  >(
+                      &self,
+                  ) -> &QueryState<NewQ, NewF> {
+                      &*(self as *const QueryState<Q, F> as *const QueryState<NewQ, NewF>)

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DJMcNab Jul 1, 2022

This does not spark joy.

I am however reasonably convinced that this is sound (I haven't dared look at the mess of query traits otherwise, but I don't think this API can ever have language level UB).

I feel like it should be possible to seperate the implementation of WorldQuery from the state in WorldQueryState, somehow.

At the very least, we could split out all the non-Q/F state fields into a sub-struct, so that they are not forced into the pessimisation of repr(C).

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BoxyUwU Jul 1, 2022

oh splitting into a separate struct is really smart thanks

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BoxyUwU Jul 1, 2022

I don't know what you mean by WorldQueryState theres no item named that anywhere in bevy_ecs.

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DJMcNab Jul 2, 2022

My apologies. I meant QueryState.

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Just one final nit. This looks generally workable. Preferably I would have liked for the transmute-esque code to stay localized to bevy_ecs::query, but likely unavoidable given the current structure.

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tim-blackbird mentioned this pull request

Add methods for joining queries with lists. #5075

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[Merged by Bors] - make WorldQuery very flat #5205

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BoxyUwU force-pushed the remove_QF_generics branch from bdfcc0c to f946a59 Compare

July 4, 2022 22:51

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Replace many_for_each_mut with iter_many_mut. #5313

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          remove QF generics from all Query/State methods

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This looks correct to me and I love the improved clarity of the apis, but I'd like to have one last conversation about the transmute behavior.

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          add warning to not do stuff with Q or F >:)

5dad4fe

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cart commented Jul 19, 2022

bors r+

bors bot pushed a commit that referenced this pull request


          remove QF generics from all Query/State methods and types (#5170)

1ac8a47

# Objective

remove `QF` generics from a bunch of types and methods on query related items. this has a few benefits:
- simplifies type signatures `fn iter(&self) -> QueryIter<'_, 's, Q::ReadOnly, F::ReadOnly>` is (imo) conceptually simpler than `fn iter(&self) -> QueryIter<'_, 's, Q, ROQueryFetch<'_, Q>, F>`
- `Fetch` is mostly an implementation detail but previously we had to expose it on every `iter` `get` etc method
- Allows us to potentially in the future simplify the `WorldQuery` trait hierarchy by removing the `Fetch` trait

## Solution

remove the `QF` generic and add a way to (unsafely) turn `&QueryState<Q1, F1>` into `&QueryState<Q2, F2>`

---

## Changelog/Migration Guide

The `QF` generic was removed from various `Query` iterator types and some methods, you should update your code to use the type of the corresponding worldquery of the fetch type that was being used, or call `as_readonly`/`as_nop` to convert a querystate to the appropriate type. For example:
`.get_single_unchecked_manual::<ROQueryFetch<Q>>(..)` -> `.as_readonly().get_single_unchecked_manual(..)`
`my_field: QueryIter<'w, 's, Q, ROQueryFetch<'w, Q>, F>` -> `my_field: QueryIter<'w, 's, Q::ReadOnly, F::ReadOnly>`

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bors bot commented Jul 19, 2022

Pull request successfully merged into main.

Build succeeded:

bors bot changed the title ~~remove QF generics from all Query/State methods and types~~ [Merged by Bors] - remove QF generics from all Query/State methods and types

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inodentry pushed a commit to IyesGames/bevy that referenced this pull request


          remove QF generics from all Query/State methods and types (bevyengi…

…ne#5170)

# Objective

remove `QF` generics from a bunch of types and methods on query related items. this has a few benefits:
- simplifies type signatures `fn iter(&self) -> QueryIter<'_, 's, Q::ReadOnly, F::ReadOnly>` is (imo) conceptually simpler than `fn iter(&self) -> QueryIter<'_, 's, Q, ROQueryFetch<'_, Q>, F>`
- `Fetch` is mostly an implementation detail but previously we had to expose it on every `iter` `get` etc method
- Allows us to potentially in the future simplify the `WorldQuery` trait hierarchy by removing the `Fetch` trait

## Solution

remove the `QF` generic and add a way to (unsafely) turn `&QueryState<Q1, F1>` into `&QueryState<Q2, F2>`

---

## Changelog/Migration Guide

The `QF` generic was removed from various `Query` iterator types and some methods, you should update your code to use the type of the corresponding worldquery of the fetch type that was being used, or call `as_readonly`/`as_nop` to convert a querystate to the appropriate type. For example:
`.get_single_unchecked_manual::<ROQueryFetch<Q>>(..)` -> `.as_readonly().get_single_unchecked_manual(..)`
`my_field: QueryIter<'w, 's, Q, ROQueryFetch<'w, Q>, F>` -> `my_field: QueryIter<'w, 's, Q::ReadOnly, F::ReadOnly>`

james7132 pushed a commit to james7132/bevy that referenced this pull request


          remove QF generics from all Query/State methods and types (bevyengi…

02e4386

…ne#5170)

# Objective

remove `QF` generics from a bunch of types and methods on query related items. this has a few benefits:
- simplifies type signatures `fn iter(&self) -> QueryIter<'_, 's, Q::ReadOnly, F::ReadOnly>` is (imo) conceptually simpler than `fn iter(&self) -> QueryIter<'_, 's, Q, ROQueryFetch<'_, Q>, F>`
- `Fetch` is mostly an implementation detail but previously we had to expose it on every `iter` `get` etc method
- Allows us to potentially in the future simplify the `WorldQuery` trait hierarchy by removing the `Fetch` trait

## Solution

remove the `QF` generic and add a way to (unsafely) turn `&QueryState<Q1, F1>` into `&QueryState<Q2, F2>`

---

## Changelog/Migration Guide

The `QF` generic was removed from various `Query` iterator types and some methods, you should update your code to use the type of the corresponding worldquery of the fetch type that was being used, or call `as_readonly`/`as_nop` to convert a querystate to the appropriate type. For example:
`.get_single_unchecked_manual::<ROQueryFetch<Q>>(..)` -> `.as_readonly().get_single_unchecked_manual(..)`
`my_field: QueryIter<'w, 's, Q, ROQueryFetch<'w, Q>, F>` -> `my_field: QueryIter<'w, 's, Q::ReadOnly, F::ReadOnly>`

ItsDoot pushed a commit to ItsDoot/bevy that referenced this pull request


          remove QF generics from all Query/State methods and types (bevyengi…

13de06f

…ne#5170)

# Objective

remove `QF` generics from a bunch of types and methods on query related items. this has a few benefits:
- simplifies type signatures `fn iter(&self) -> QueryIter<'_, 's, Q::ReadOnly, F::ReadOnly>` is (imo) conceptually simpler than `fn iter(&self) -> QueryIter<'_, 's, Q, ROQueryFetch<'_, Q>, F>`
- `Fetch` is mostly an implementation detail but previously we had to expose it on every `iter` `get` etc method
- Allows us to potentially in the future simplify the `WorldQuery` trait hierarchy by removing the `Fetch` trait

## Solution

remove the `QF` generic and add a way to (unsafely) turn `&QueryState<Q1, F1>` into `&QueryState<Q2, F2>`

---

## Changelog/Migration Guide

The `QF` generic was removed from various `Query` iterator types and some methods, you should update your code to use the type of the corresponding worldquery of the fetch type that was being used, or call `as_readonly`/`as_nop` to convert a querystate to the appropriate type. For example:
`.get_single_unchecked_manual::<ROQueryFetch<Q>>(..)` -> `.as_readonly().get_single_unchecked_manual(..)`
`my_field: QueryIter<'w, 's, Q, ROQueryFetch<'w, Q>, F>` -> `my_field: QueryIter<'w, 's, Q::ReadOnly, F::ReadOnly>`

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