add shadow-compatible quinn-udp fallback

[bomanaps]

Shadow

[ArtiomTr]

I'm completely lost - this is for testing, right? Why is it patched for everything - including prod builds?

[bomanaps]

This pr should be in it own branch with a separate image tag its just for shadow related work not to be merged in main or devnet 5 branch

[bomanaps]

I dropped a dm on Tg on this

[ArtiomTr]

ah right, now I understand. However, I think maintaining two different versions can be too much burden. I think it should be possible to configure this via separate profile (https://doc.rust-lang.org/cargo/reference/profiles.html). Then, we can merge this, and build two images for all devnet-* branches

[bomanaps]

Profiles can't toggle [patch.crates-io] they only control codegen flags, but we can drop the patch block from Cargo.toml and have CI apply it only for the shadow image via cargo build --release --config 'patch.crates-io.quinn-udp.path="rust/patch/quinn-udp"' so we have one branch, two images, no source divergence if this will be better?

[ArtiomTr]

ye it is better, but still not good enough. First of all, better to keep this stuff in Makefile, so it can be executed locally. Second, you probably can do some trick like:

# Root Cargo.toml
[profile.shadow]
rustflags = ["--cfg", "shadow_mode"]

# P2P crate's Cargo.toml
[target.'cfg(shadow_mode)'.dependencies]
quinn-udp = { path = '..some path..' }

[target.'cfg(not(shadow_mode))'.dependencies]
quinn-udp = '..some version..'

This will probably be more maintainable

[bomanaps]

Thanks for the pointer, but that cfg-target swap only works when a crate directly depends on quinn-udp here we pull it in transitively through libp2p-quic, so there's nothing in our Cargo.toml files to swap, to redirect a transitive dependency, Cargo will only gives us [patch.crates-io], so I will keep the patch block out of source and apply it via --config from a make shadow-* target this way the same command works locally and in CI, while production stays untouched.