fectchcargo: don't break old sha256

pkgs/build-support/rust/default.nix

@@ -17,15 +17,9 @@ in
 , cargoBuildFlags ? []
 
 , cargoVendorDir ? null
-# This tells cargo-vendor to include a Cargo config file in the fixed-output
-# derivation. This is desirable in every case, so please set it to true.
-# Eventually this will default to true and even later this option and the old
-# behaviour will be removed.
-, useRealVendorConfig ? false
 , ... } @ args:
 
 assert cargoVendorDir == null -> cargoSha256 != "unset";
-assert cargoVendorDir != null -> !useRealVendorConfig;
 
 let
   cargoDeps = if cargoVendorDir == null
@@ -33,7 +27,6 @@ let
         inherit name src srcs sourceRoot cargoUpdateHook;
         patches = cargoPatches;
         sha256 = cargoSha256;
-        writeVendorConfig = useRealVendorConfig;
       }
     else null;
 
@@ -68,19 +61,12 @@ in stdenv.mkDerivation (args // {
     ${setupVendorDir}
 
     mkdir .cargo
-  '' + (if useRealVendorConfig then ''
-      substitute "$(pwd)/$cargoDepsCopy/.cargo/config" .cargo/config \
-      --subst-var-by vendor "$(pwd)/$cargoDepsCopy"
-    '' else ''
-      cat >.cargo/config <<-EOF
-        [source.crates-io]
-        registry = 'https://github.com/rust-lang/crates.io-index'
-        replace-with = 'vendored-sources'
-
-        [source.vendored-sources]
-        directory = '$(pwd)/$cargoDepsCopy'
-      EOF
-    '') + ''
+    config="$(pwd)/$cargoDepsCopy/.cargo/config";
+    if [[ ! -e $config ]]; then
+      config=${./fetchcargo-default-config.toml};
+    fi;
+    substitute $config .cargo/config \
+    --subst-var-by vendor "$(pwd)/$cargoDepsCopy"
 
     unset cargoDepsCopy
 

pkgs/build-support/rust/fetchcargo-default-config.toml

@@ -0,0 +1,7 @@
+[source."crates-io"]
+"replace-with" = "vendored-sources"
+
+[source."vendored-sources"]
+"directory" = "@vendor@"
+
+

pkgs/build-support/rust/fetchcargo.nix

@@ -1,5 +1,4 @@
 { 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;
@@ -9,9 +8,10 @@ let cargo-vendor-normalise = stdenv.mkDerivation {
   preferLocalBuild = true;
 };
 in
+{ name ? "cargo-deps", src, srcs, patches, sourceRoot, sha256, cargoUpdateHook ? "" }:
 stdenv.mkDerivation {
   name = "${name}-vendor";
-  nativeBuildInputs = [ cacert cargo-vendor git rust.cargo ];
+  nativeBuildInputs = [ cacert cargo-vendor git cargo-vendor-normalise rust.cargo ];
   inherit src srcs patches sourceRoot;
 
   phases = "unpackPhase patchPhase installPhase";
@@ -33,10 +33,15 @@ stdenv.mkDerivation {
     ${cargoUpdateHook}
 
     mkdir -p $out
-    cargo vendor $out > config
-  '' + stdenv.lib.optionalString writeVendorConfig ''
-    mkdir $out/.cargo
-    < config ${cargo-vendor-normalise}/bin/cargo-vendor-normalise > $out/.cargo/config
+    cargo vendor $out | cargo-vendor-normalise > config
+    # fetchcargo used to never keep the config output by cargo vendor
+    # and instead hardcode the config in ./fetchcargo-default-config.toml.
+    # This broke on packages needing git dependencies, so now we keep the config.
+    # But not to break old cargoSha256, if the previous behavior was enough,
+    # we don't store the config.
+    if ! cmp config ${./fetchcargo-default-config.toml} > /dev/null; then
+      install -Dt $out/.cargo config;
+    fi;
   '';
 
   outputHashAlgo = "sha256";