change not implemation to custom system struct #8105

B-Reif · 2023-03-16T03:55:16Z

Objective

The function common_conditions::not can't be used with the system configuration distributive_run_if, because the returned closure is typed as impl Condition<()>. Fixes another part of #8058.

Solution

Changes to not:

Add a custom NotSystem struct which wraps a Condition and inverts its output whenever it's run. Implements Clone.
Return the concrete NotSystem<_, T> type from not<_, T>, so that the return type is Clone when the input system is Clone.

Changes to FunctionSystem:

Add a Clone implementation for FunctionSystem<Marker, F> where F is Clone. Note: this implementation does not clone the param_state field, so the cloned system instance doesn't have the original's state. Let me know if this is a problem.
~~#[derive(Clone)] for the IsFunctionSystem marker. The compiler didn't like it when I tried to remove this. Is it really necessary to implement Clone for the marker types?~~

Changelog

Added NotSystem system type
Changed common_conditions::not to return a concrete type
Changed FunctionSystem to implement Clone for Clone functions

B-Reif · 2023-03-16T03:59:14Z

I accidentally removed some of the common_conditions tests while resolving conflicts in #8060, so this PR also re-adds them.

JoJoJet · 2023-03-16T04:06:09Z

#[derive(Clone)] for the IsFunctionSystem marker. The compiler didn't like it when I tried to remove this. Is it really necessary to implement Clone for the marker types?

The reason for this is right here:

#[derive(Clone)]
pub struct ConditionInverter<Marker, T>

When using #[derive(Clone)], the compiler (incorrectly) adds a Marker: Clone bound. To fix this you'd have to do a manual implementation of Clone.

I will do a full review later.

JoJoJet

It's a bit unfortunate to have to add another manual System impl, but I think it's absolutely worth it to make run conditions just work in more situations.

crates/bevy_ecs/src/schedule/condition.rs

JoJoJet · 2023-03-16T20:59:25Z

Add a Clone implementation for FunctionSystem<Marker, F> where F is Clone. Note: this implementation does not clone the param_state field, so the cloned system instance doesn't have the original's state. Let me know if this is a problem.

Essentially, this just means that cloned function systems will have their initialization undone. I think that's acceptable -- however the current implementation does not fully de-initialize the system. You'd need to make it reset the world_id, archetype_generation, and probably the system_meta.

Also, it might be worth adding a SystemClone trait instead of using std's Clone. It would make it easier to document the de-initialization behavior, and make it more difficult to misuse.

Alternatively, we could retain the initialization when cloning, but require the system's state to be Clone.

JoJoJet

Thank you for taking my suggestions. Generally I'm on board with this PR, but I'd like more opinions on how to handle the initialization issue.

crates/bevy_ecs/src/schedule/condition.rs

alice-i-cecile · 2023-03-16T23:19:26Z

I'd definitely prefer if this reset the system initialization completely. I don't care about performance here, and I think that not doing so is a correctness footgun.

…tionSystem

B-Reif · 2023-03-17T01:28:51Z

Thank you for taking my suggestions.

Thank you very much for your guidance!

I'd definitely prefer if this reset the system initialization completely.

I've changed the Clone implementation to only clone the func; other fields now match the IntoSystem implementation.

alice-i-cecile

I think this safety comment is clearer, but I won't block on it. Other changes look good.

crates/bevy_ecs/src/schedule/condition.rs

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

JoJoJet · 2023-03-17T11:08:44Z

crates/bevy_ecs/src/system/function_system.rs

+// De-initializes the cloned system.
+impl<Marker, F> Clone for FunctionSystem<Marker, F>
+where
+    F: SystemParamFunction<Marker> + Clone,


This behavior, while probably correct, is very subtle. It needs to be documented somewhere visible -- perhaps on the System trait? Also, maybe it should be documented on distributive_run_if, since I think that's the only place we're cloning systems right now.

Right now Clone is implemented specifically for FunctionSystem, and not necessarily for other System implementers. I think it makes more sense to call it out on FunctionSystem. I also added a note on distributive_run_if.

Right now Clone is implemented specifically for FunctionSystem, and not necessarily for other System implementers.

Right, but users will rarely if ever interact with the FunctionSystem type directly. I think it's more likely to be seen if the System trait mentions that systems defined using a fn have this property.

Why is this resolved?

This was addressed below in 3a98270.

That documented it on FunctionSystem, but users have little reason to ever interact with that type or read its documentation. Function systems get automagically created through type magic, so many users are probably only vaguely aware of that type's existence because of compiler errors.

…ition-inverter

JoJoJet · 2023-03-17T20:40:26Z

crates/bevy_ecs/src/system/function_system.rs

+// De-initializes the cloned system.
+impl<Marker, F> Clone for FunctionSystem<Marker, F>
+where
+    F: SystemParamFunction<Marker> + Clone,


Right now Clone is implemented specifically for FunctionSystem, and not necessarily for other System implementers.

Right, but users will rarely if ever interact with the FunctionSystem type directly. I think it's more likely to be seen if the System trait mentions that systems defined using a fn have this property.

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

B-Reif added 2 commits March 15, 2023 20:44

change not implemation to custom system struct

5ed8021

remove some clone calls

6f5e3db

JoJoJet self-requested a review March 16, 2023 04:01

manually impl clone, remove clone from marker

f53d33a

JoJoJet suggested changes Mar 16, 2023

View reviewed changes

B-Reif added 2 commits March 16, 2023 13:39

remove marker type

858ef20

rename, remove readonly bound

f16e72b

JoJoJet reviewed Mar 16, 2023

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crates/bevy_ecs/src/schedule/condition.rs Outdated Show resolved Hide resolved

JoJoJet requested a review from alice-i-cecile March 16, 2023 21:00

use std::ops::Not

6b65346

JoJoJet reviewed Mar 16, 2023

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crates/bevy_ecs/src/schedule/condition.rs Outdated Show resolved Hide resolved

B-Reif added 3 commits March 16, 2023 18:16

relax type requirements

57f1cb6

clear world_id, system_meta, and archetype_generation for cloned Func…

055c7b4

…tionSystem

reorder fields

3338d57

alice-i-cecile approved these changes Mar 17, 2023

View reviewed changes

crates/bevy_ecs/src/schedule/condition.rs Outdated Show resolved Hide resolved

Update crates/bevy_ecs/src/schedule/condition.rs

fa0aa35

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

JoJoJet reviewed Mar 17, 2023

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B-Reif added 2 commits March 17, 2023 12:06

add doc comments for FunctionSystem and distributive_run_if

3a98270

Merge branch 'condition-inverter' of github.com:B-Reif/bevy into cond…

e68de94

…ition-inverter

JoJoJet approved these changes Mar 17, 2023

View reviewed changes

alice-i-cecile added S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it A-ECS Entities, components, systems, and events C-Usability A simple quality-of-life change that makes Bevy easier to use labels Mar 17, 2023

alice-i-cecile added this to the 0.10.1 milestone Mar 17, 2023

alice-i-cecile added this pull request to the merge queue Mar 17, 2023

alice-i-cecile merged commit bca4b36 into bevyengine:main Mar 17, 2023
23 checks passed

B-Reif deleted the condition-inverter branch March 17, 2023 22:40

Shfty pushed a commit to shfty-rust/bevy that referenced this pull request Mar 19, 2023

change not implemation to custom system struct (bevyengine#8105)

27adaa3

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

Shfty pushed a commit to shfty-rust/bevy that referenced this pull request Mar 19, 2023

change not implemation to custom system struct (bevyengine#8105)

05e155d

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

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change not implemation to custom system struct #8105

change not implemation to custom system struct #8105

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change not implemation to custom system struct #8105

change not implemation to custom system struct #8105

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B-Reif commented Mar 16, 2023 • edited

Objective

Solution

Changelog

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