Use `cargo-deny` to prevent duplicate dependencies

[emilk]

By running cargo-deny on CI for all supported platforms, we can ensure users of accesskit won't have duplicated dependencies. Reducing duplicated dependencies reduces compile times and binary bloat.

Here's how it is done in winit, for instance:

https://github.com/rust-windowing/winit/blob/4d4d6e5052877d9578bac73f52eaf323e9089998/.github/workflows/ci.yml#L180-L203

and their deny.toml:

https://github.com/rust-windowing/winit/blob/master/deny.toml

[mwcampbell]

@emilk Thanks for the feedback. We actually already added cargo deny in a recent PR. I guess our deny.toml might need tweaking though. Are you having a problem now with AccessKit introducing duplicate dependencies in egui?

[emilk]

Oh sorry, I thought I checked first 🤦

Yeah I got some duplicated deps via accesskit-winit and accesskit-unix… I'll see if I can reproduce

[mwcampbell]

We haven't actually published a release since adding cargo deny.

[emilk]

Ah, yes, the deny.toml does not prevent duplicated dependencies. What is needed is:

--- a/deny.toml
+++ b/deny.toml
@@ -34,7 +34,7 @@ exceptions = [
 ]
 
 [bans]
-multiple-versions = "warn"
+multiple-versions = "deny"
 wildcards = "allow"
 highlight = "all"
 workspace-default-features = "allow"

and then duplicates popup fast when checking different platforms with

cargo deny --all-features --log-level error --target aarch64-apple-darwin check
cargo deny --all-features --log-level error --target aarch64-linux-android check
cargo deny --all-features --log-level error --target i686-pc-windows-gnu check
cargo deny --all-features --log-level error --target i686-pc-windows-msvc check
cargo deny --all-features --log-level error --target i686-unknown-linux-gnu check
cargo deny --all-features --log-level error --target wasm32-unknown-unknown check
cargo deny --all-features --log-level error --target x86_64-apple-darwin check
cargo deny --all-features --log-level error --target x86_64-pc-windows-gnu check
cargo deny --all-features --log-level error --target x86_64-pc-windows-msvc check
cargo deny --all-features --log-level error --target x86_64-unknown-linux-gnu check
cargo deny --all-features --log-level error --target x86_64-unknown-linux-musl check
cargo deny --all-features --log-level error --target x86_64-unknown-redox check

Some are small things like raw-window-handle that should just be ignored, but there are also a lot of large crates that are duplicated.

There are for instance multiple version of socket2, polling, event-listener, async-channel, objc2-encode, …

[DataTriny]

Hello,

I won't comment about deny.toml needing some tweaking at this time, getting rid of the remaining duplicates might not be that easy.

I just wanted to say that I don't think we need to run cargo deny on each platform. My guess is that's because we're checking out Cargo.lock into the repo, so the dependency graph is already there for the tool to explore. Passing different values to the --target option seem to always yield the same results.