Include cargo dependencies in the Nix tarball

nix-rust/local.mk

@@ -4,4 +4,6 @@ libnixrust_LDFLAGS_USE := -L$(d)/target/release -lnixrust -ldl
 libnixrust_LDFLAGS_USE_INSTALLED := $(libnixrust_LDFLAGS_USE)
 
 $(d)/target/release/libnixrust.a: $(wildcard $(d)/src/*.rs) $(d)/Cargo.toml
-	$(trace-gen) cd nix-rust && RUSTC_BOOTSTRAP=1 cargo build --release && touch target/release/libnixrust.a
+	$(trace-gen) cd nix-rust && CARGO_HOME=$$(if [[ -d vendor ]]; then echo vendor; fi) cargo build --release -Z offline && touch target/release/libnixrust.a
+
+dist-files += $(d)/vendor

release.nix

@@ -10,6 +10,43 @@ let
 
   jobs = rec {
 
+    # Create a "vendor" directory that contains the crates listed in
+    # Cargo.lock, and include it in the Nix tarball. This allows Nix
+    # to be built without network access.
+    vendoredCrates =
+      let
+        lockFile = builtins.fromTOML (builtins.readFile nix-rust/Cargo.lock);
+
+        files = map (pkg: import <nix/fetchurl.nix> {
+          url = "https://crates.io/api/v1/crates/${pkg.name}/${pkg.version}/download";
+          sha256 = lockFile.metadata."checksum ${pkg.name} ${pkg.version} (registry+https://github.com/rust-lang/crates.io-index)";
+        }) (builtins.filter (pkg: pkg.source or "" == "registry+https://github.com/rust-lang/crates.io-index") lockFile.package);
+
+      in pkgs.runCommand "cargo-vendor-dir" {}
+        ''
+          mkdir -p $out/vendor
+
+          cat > $out/vendor/config <<EOF
+          [source.crates-io]
+          replace-with = "vendored-sources"
+
+          [source.vendored-sources]
+          directory = "vendor"
+          EOF
+
+          ${toString (builtins.map (file: ''
+            mkdir $out/vendor/tmp
+            tar xvf ${file} -C $out/vendor/tmp
+            dir=$(echo $out/vendor/tmp/*)
+
+            # Add just enough metadata to keep Cargo happy.
+            printf '{"files":{},"package":"${file.outputHash}"}' > "$dir/.cargo-checksum.json"
+
+            mv "$dir" $out/vendor/
+            rmdir $out/vendor/tmp
+          '') files)}
+        '';
+
 
     tarball =
       with pkgs;
@@ -38,6 +75,8 @@ let
 
         distPhase =
           ''
+            cp -prd ${vendoredCrates}/vendor/ nix-rust/vendor/
+
             runHook preDist
             make dist
             mkdir -p $out/tarballs