Generic SystemParam impls for Option and Result
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alice-i-cecile
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I thought I added one? Did I put it in the wrong place? |
alice-i-cecile
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…n-param # Conflicts: # crates/bevy_ecs/src/system/builder.rs # crates/bevy_ecs/src/system/system_param.rs
cBournhonesque
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andrewzhurov
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# Objective Provide a generic `impl SystemParam for Option<P>` that uses system parameter validation. This immediately gives useful impls for params like `EventReader` and `GizmosState` that are defined in terms of `Res`. It also allows third-party system parameters to be usable with `Option`, which was previously impossible due to orphan rules. Note that this is a behavior change for `Option<Single>`. It currently fails validation if there are multiple matching entities, but with this change it will pass validation and produce `None`. Also provide an impl for `Result<P, SystemParamValidationError>`. This allows systems to inspect the error if necessary, either for bubbling it up or for checking the `skipped` flag. Fixes bevyengine#12634 Fixes bevyengine#14949 Related to bevyengine#18516 ## Solution Add generic `SystemParam` impls for `Option` and `Result`, and remove the impls for specific types. Update documentation and `fallible_params` example with the new semantics for `Option<Single>`.
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Objective
Provide a generic
impl SystemParam for Option<P>that uses system parameter validation. This immediately gives useful impls for params likeEventReaderandGizmosStatethat are defined in terms ofRes. It also allows third-party system parameters to be usable withOption, which was previously impossible due to orphan rules.Note that this is a behavior change for
Option<Single>. It currently fails validation if there are multiple matching entities, but with this change it will pass validation and produceNone.Also provide an impl for
Result<P, SystemParamValidationError>. This allows systems to inspect the error if necessary, either for bubbling it up or for checking theskippedflag.Fixes #12634
Fixes #14949
Related to #18516
Solution
Add generic
SystemParamimpls forOptionandResult, and remove the impls for specific types.Update documentation and
fallible_paramsexample with the new semantics forOption<Single>.