fetchcargo: normalise cargo config to ensure determinism

pkgs/build-support/rust/cargo-vendor-normalise.py

@@ -0,0 +1,32 @@
+#!/usr/bin/env python
+
+import toml
+import sys
+
+def escape(s):
+    return '"'+s.replace('"', r'\"').replace("\n", r"\n").replace("\\", "\\\\")+'"'
+
+data = toml.load(sys.stdin)
+
+assert list(data.keys()) == [ "source" ]
+
+# this value is non deterministic
+data["source"]["vendored-sources"]["directory"] = "@vendor@"
+
+result = ""
+inner = data["source"]
+for source in sorted(inner.keys()):
+    result += '[source.{}]\n'.format(escape(source))
+    if source == "vendored-sources":
+        result += '"directory" = "@vendor@"\n'
+    else:
+        for key in sorted(inner[source].keys()):
+            result += '{} = {}\n'.format(escape(key), escape(inner[source][key]))
+    result += "\n"
+
+real = toml.loads(result)
+assert real == data, "output = {} while input = {}".format(real, data)
+
+print(result)
+
+

pkgs/build-support/rust/default.nix

@@ -1,7 +1,7 @@
-{ stdenv, cacert, git, rust, cargo-vendor }:
+{ stdenv, cacert, git, rust, cargo-vendor, python3 }:
 let
   fetchcargo = import ./fetchcargo.nix {
-    inherit stdenv cacert git rust cargo-vendor;
+    inherit stdenv cacert git rust cargo-vendor python3;
   };
 in
 { name, cargoSha256 ? "unset"
@@ -69,8 +69,8 @@ in stdenv.mkDerivation (args // {
 
     mkdir .cargo
   '' + (if useRealVendorConfig then ''
-      sed "s|directory = \".*\"|directory = \"$(pwd)/$cargoDepsCopy\"|g" \
-        "$(pwd)/$cargoDepsCopy/.cargo/config" > .cargo/config
+      substitute "$(pwd)/$cargoDepsCopy/.cargo/config" .cargo/config \
+      --subst-var-by vendor "$(pwd)/$cargoDepsCopy"
     '' else ''
       cat >.cargo/config <<-EOF
         [source.crates-io]

pkgs/build-support/rust/fetchcargo.nix

@@ -1,5 +1,14 @@
-{ stdenv, cacert, git, rust, cargo-vendor }:
+{ stdenv, cacert, git, rust, cargo-vendor, python3 }:
 { name ? "cargo-deps", src, srcs, patches, sourceRoot, sha256, cargoUpdateHook ? "", writeVendorConfig ? false }:
+let cargo-vendor-normalise = stdenv.mkDerivation {
+  name = "cargo-vendor-normalise";
+  src = ./cargo-vendor-normalise.py;
+  unpackPhase = ":";
+  installPhase = "install -D $src $out/bin/cargo-vendor-normalise";
+  buildInputs = [ (python3.withPackages(ps: [ ps.toml ])) ];
+  preferLocalBuild = true;
+};
+in
 stdenv.mkDerivation {
   name = "${name}-vendor";
   nativeBuildInputs = [ cacert cargo-vendor git rust.cargo ];
@@ -27,7 +36,7 @@ stdenv.mkDerivation {
     cargo vendor $out > config
   '' + stdenv.lib.optionalString writeVendorConfig ''
     mkdir $out/.cargo
-    sed "s|directory = \".*\"|directory = \"./vendor\"|g" config > $out/.cargo/config
+    < config ${cargo-vendor-normalise}/bin/cargo-vendor-normalise > $out/.cargo/config
   '';
 
   outputHashAlgo = "sha256";