feat(tvix/nix-compat-derive): Add deriver for NixDeserialize

This adds a nix-compat-derive derive crate that implements a deriver
for NixDeserialize implementations. This is to reduce the amount of
code needed to implement deserialization for all the types used by
the Nix daemon protocol.

Change-Id: I484724b550e8a1d5e9adad9555d9dc1374ae95c2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12022
Autosubmit: Brian Olsen <me@griff.name>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

tvix/nix-compat/Cargo.toml

@@ -8,9 +8,10 @@ edition = "2021"
 async = ["tokio"]
 # code emitting low-level packets used in the daemon protocol.
 wire = ["tokio", "pin-project-lite", "bytes"]
+test = []
 
 # Enable all features by default.
-default = ["async", "wire"]
+default = ["async", "wire", "nix-compat-derive"]
 
 [dependencies]
 bitflags = "2.4.1"
@@ -33,6 +34,11 @@ tracing = "0.1.37"
 optional = true
 version = "1.6.1"
 
+[dependencies.nix-compat-derive]
+path = "../nix-compat-derive"
+optional = true
+default-features = false
+
 [dependencies.tokio]
 optional = true
 version = "1.32.0"

tvix/nix-compat/src/nix_daemon/protocol_version.rs

@@ -54,6 +54,13 @@ impl From<u16> for ProtocolVersion {
     }
 }
 
+#[cfg(any(test, feature = "test"))]
+impl From<(u8, u8)> for ProtocolVersion {
+    fn from((major, minor): (u8, u8)) -> Self {
+        Self::from_parts(major, minor)
+    }
+}
+
 impl TryFrom<u64> for ProtocolVersion {
     type Error = &'static str;