[Merged by Bors] - Added documentation on the query filters

[sdfgeoff]

This documents both the non-obvious interaction with non-explicit system ordering
and adds examples for Changed and Added. This likely closes #1551

[sdfgeoff]

Hmm, I'm not familiar enough with rustdoc to figure out how to make those examples pass CI. Can someone give me some pointers?

[Ratysz]

cargo test --doc in bevy_ecs directory.

Oh, I see what the issue is. I'm fairly sure you can't use bevy there because bevy_ecs does not depend on bevy; you should be able to import stuff from bevy_ecs and hide it from the doc with a #, like # use bevy_ecs::prelude::*;.

[mockersf]

you can't use use bevy::prelude::*; from inside bevy_ecs, you will need to use a more direct path to the struct you want to use... and as bevy_ecs is one of the core crate, you don't have access to a lot of stuff without adding dev dependencies.

Mutated, Added and Changed should be reachable as they are defined here, but you can't use Name or Transform. Simplest solution would probably to create struct in the doc example and have them hidden, see https://doc.rust-lang.org/rustdoc/documentation-tests.html#hiding-portions-of-the-example

[sdfgeoff]

Thanks for the review! Yup, I've got the examples compiling by using bevy_ecs:: and hiding some structs.

[mockersf]

no need to wrap the types in tuples, you can have

fn print_moving_objects_system(query: Query<Name, Mutated<Transform>>) {
    for name in query.iter() {
        println!("Entity Moved: {}", name)
    }
}

[sdfgeoff]

Cool! I didn't know that, I've been putting all my queries in tuples.......

[mockersf]

also, #1525 is changing the location of those structs, let's see what gets merged first 😄

[mockersf]

now defined here

[sdfgeoff]

Updated :)

[cart]

bors r+

[bors]

Pull request successfully merged into main.

Build succeeded:

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