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Introduce Populated system param #15302

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MiniaczQ opened this issue Sep 19, 2024 · 5 comments · Fixed by #15488
Closed

Introduce Populated system param #15302

MiniaczQ opened this issue Sep 19, 2024 · 5 comments · Fixed by #15488
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@MiniaczQ
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A-ECS Entities, components, systems, and events C-Feature A new feature, making something new possible S-Ready-For-Implementation This issue is ready for an implementation PR. Go for it! X-Contentious There are nontrivial implications that should be thought through

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@MiniaczQ
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MiniaczQ commented Sep 19, 2024 •
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What problem does this solve or what need does it fill?

There have been many requests to not run systems if there is nothing to process (in a query).
The Populated system param would do exactly that.

What solution would you like?

Add Populated system param that fails validation if query is empty.
@MiniaczQ MiniaczQ added C-Feature A new feature, making something new possible S-Needs-Triage This issue needs to be labelled A-ECS Entities, components, systems, and events X-Contentious There are nontrivial implications that should be thought through and removed S-Needs-Triage This issue needs to be labelled labels Sep 19, 2024
@MiniaczQ MiniaczQ mentioned this issue Sep 19, 2024
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@alice-i-cecile
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I'm in favor of this existing: seems quite useful once #15276 is merged. This is a sibling to #15264.

I'd be interested in adding a NonEmptyEventReader as well, either in the same PR or in a separate one.

@benfrankel
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Bikeshedding, but would QueryNonEmpty be a better name? It'd be next to Query and QuerySingle alphabetically and in code-completion.

@alice-i-cecile
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I think that's a bit better, yeah.

@MiniaczQ
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I prefer proper spelling, all of them will show up when typing "Query"
I'm fine either way

@MiniaczQ
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Second thoughts, maybe we should skip Query entirely, assuming we're moving more things to entities, this will naturally show up more so we don't need to be worried about awareness

@MiniaczQ MiniaczQ mentioned this issue Sep 23, 2024
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github-merge-queue bot pushed a commit that referenced this issue Sep 23, 2024
@MiniaczQ
Reduce runtime panics through SystemParam validation (#15276)
e312da8 
# Objective

The goal of this PR is to introduce `SystemParam` validation in order to
reduce runtime panics.

Fixes #15265

## Solution

`SystemParam` now has a new method `validate_param(...) -> bool`, which
takes immutable variants of `get_param` arguments. The returned value
indicates whether the parameter can be acquired from the world. If
parameters cannot be acquired for a system, it won't be executed,
similarly to run conditions. This reduces panics when using params like
`Res`, `ResMut`, etc. as well as allows for new, ergonomic params like
#15264 or #15302.

Param validation happens at the level of executors. All validation
happens directly before executing a system, in case of normal systems
they are skipped, in case of conditions they return false.

Warning about system skipping is primitive and subject to change in
subsequent PRs.

## Testing

Two executor tests check that all executors:
- skip systems which have invalid parameters:
  - piped systems get skipped together,
  - dependent systems still run correctly,
- skip systems with invalid run conditions:
  - system conditions have invalid parameters,
  - system set conditions have invalid parameters.
@MiniaczQ MiniaczQ added the S-Ready-For-Implementation This issue is ready for an implementation PR. Go for it! label Sep 23, 2024
This was referenced Sep 23, 2024
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@MiniaczQ MiniaczQ changed the title Introduce NonEmptyQuery system param Introduce Populated system param Sep 29, 2024
github-merge-queue bot pushed a commit that referenced this issue Sep 30, 2024
@MiniaczQ @alice-i-cecile
Populated (query) system param (#15488)
fc93e13 
# Objective

Add a `Populated` system parameter that acts like `Query`, but prevents
system from running if there are no matching entities.

Fixes: #15302

## Solution

Implement the system param which newtypes the `Query`.
The only change is new validation, which fails if query is empty.

The new system param is used in `fallible_params` example.

## Testing

Ran `fallible_params` example.

---------

Co-authored-by: Alice Cecile <[email protected]>
robtfm pushed a commit to robtfm/bevy that referenced this issue Oct 4, 2024
@MiniaczQ @alice-i-cecile @robtfm
Populated (query) system param (bevyengine#15488)
ea48a84 
# Objective

Add a `Populated` system parameter that acts like `Query`, but prevents
system from running if there are no matching entities.

Fixes: bevyengine#15302

## Solution

Implement the system param which newtypes the `Query`.
The only change is new validation, which fails if query is empty.

The new system param is used in `fallible_params` example.

## Testing

Ran `fallible_params` example.

---------

Co-authored-by: Alice Cecile <[email protected]>
@MiniaczQ MiniaczQ self-assigned this Oct 20, 2024
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@MiniaczQ MiniaczQ

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A-ECS Entities, components, systems, and events C-Feature A new feature, making something new possible S-Ready-For-Implementation This issue is ready for an implementation PR. Go for it! X-Contentious There are nontrivial implications that should be thought through
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Populated (query) system param MiniaczQ/bevy
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@alice-i-cecile @benfrankel @MiniaczQ