Fix: Derive macro requiring backend crate as dependency

[MrGVSV]

Problem

Fixes a bug found by @Tsudico on Discord:

I'm trying to figure out the basic schematic example. It runs as an example in a cloned bevy_proto, but when I copy the code into a new project it fails with the following error for any derived Schematic:

message: bevy_proto_backend is present in Cargo.toml: CrateNotFound { crate_name: "bevy_proto_backend", path: "f:\Repositories\rust\projects\bevy_proto_test\Cargo.toml" }

Cargo.toml has this under dependencies:

[dependencies]
bevy = "0.10.1"
bevy_proto = "0.8"

Am I missing something in the Cargo.toml?

Solution

Since bevy_proto and bevy_proto_backend need to use the derive macro, we can't just use a feature to swap between sources. Instead, we search for one and then the other if not found.

Since this is a very problematic bug that makes bevy_proto unusable (at least, the macros), I'm going to publish this version right away and yank the previous version.