buildRustPackage: factor out build phase to cargoBuildHook

- API change: remove the `target` argument of `buildRustPackage`, the
  target should always be in sync with the C/C++ compiler that is used.

- Gathering of binaries has moved from `buildPhase` to `installPhase`,
  this simplifies the hook and orders this functionality logically
  with the installation logic.

3 files changed, 71 insertions, 43 deletions

diff --git a/pkgs/build-support/rust/default.nix b/pkgs/build-support/rust/default.nix
index 6741b329a30..19ec71261be 100644
--- a/pkgs/build-support/rust/default.nix
+++ b/pkgs/build-support/rust/default.nix
@@ -3,6 +3,7 @@
 , buildPackages
 , cacert
 , cargo
+, cargoBuildHook
 , cargoSetupHook
 , fetchCargoTarball
 , runCommandNoCC
@@ -37,7 +38,6 @@
 , cargoBuildFlags ? []
 , buildType ? "release"
 , meta ? {}
-, target ? rust.toRustTargetSpec stdenv.hostPlatform
 , cargoVendorDir ? null
 , checkType ? buildType
 , depsExtraArgs ? {}
@@ -71,6 +71,7 @@ let
   # against the src fixed-output derivation to check consistency.
   validateCargoDeps = !(cargoHash == "" && cargoSha256 == "");
 
+  target = rust.toRustTargetSpec stdenv.hostPlatform;
   targetIsJSON = lib.hasSuffix ".json" target;
   useSysroot = targetIsJSON && !__internal_dontAddSysroot;
 
@@ -86,10 +87,6 @@ let
     originalCargoToml = src + /Cargo.toml; # profile info is later extracted
   };
 
-  ccForBuild="${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}cc";
-  cxxForBuild="${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}c++";
-  ccForHost="${stdenv.cc}/bin/${stdenv.cc.targetPrefix}cc";
-  cxxForHost="${stdenv.cc}/bin/${stdenv.cc.targetPrefix}c++";
   releaseDir = "target/${shortTarget}/${buildType}";
   tmpDir = "${releaseDir}-tmp";
 
@@ -102,11 +99,17 @@ assert useSysroot -> !(args.doCheck or true);
 stdenv.mkDerivation ((removeAttrs args ["depsExtraArgs"]) // lib.optionalAttrs useSysroot {
   RUSTFLAGS = "--sysroot ${sysroot} " + (args.RUSTFLAGS or "");
 } // {
-  inherit cargoDeps;
+  inherit buildAndTestSubdir cargoDeps releaseDir tmpDir;
+
+  cargoBuildFlags = lib.concatStringsSep " " cargoBuildFlags;
+
+  cargoBuildType = "--${buildType}";
 
   patchRegistryDeps = ./patch-registry-deps;
 
-  nativeBuildInputs = nativeBuildInputs ++ [ cacert git cargo cargoSetupHook rustc ];
+  nativeBuildInputs = nativeBuildInputs ++
+    [ cacert git cargo cargoBuildHook cargoSetupHook rustc ];
+
   buildInputs = buildInputs ++ lib.optional stdenv.hostPlatform.isMinGW windows.pthreads;
 
   patches = cargoPatches ++ patches;
@@ -125,38 +128,6 @@ stdenv.mkDerivation ((removeAttrs args ["depsExtraArgs"]) // lib.optionalAttrs u
     runHook postConfigure
   '';
 
-  buildPhase = with builtins; args.buildPhase or ''
-    ${lib.optionalString (buildAndTestSubdir != null) "pushd ${buildAndTestSubdir}"}
-    runHook preBuild
-
-    (
-    set -x
-    env \
-      "CC_${rust.toRustTarget stdenv.buildPlatform}"="${ccForBuild}" \
-      "CXX_${rust.toRustTarget stdenv.buildPlatform}"="${cxxForBuild}" \
-      "CC_${rust.toRustTarget stdenv.hostPlatform}"="${ccForHost}" \
-      "CXX_${rust.toRustTarget stdenv.hostPlatform}"="${cxxForHost}" \
-      cargo build -j $NIX_BUILD_CORES \
-        ${lib.optionalString (buildType == "release") "--release"} \
-        --target ${target} \
-        --frozen ${concatStringsSep " " cargoBuildFlags}
-    )
-
-    runHook postBuild
-
-    ${lib.optionalString (buildAndTestSubdir != null) "popd"}
-
-    # This needs to be done after postBuild: packages like `cargo` do a pushd/popd in
-    # the pre/postBuild-hooks that need to be taken into account before gathering
-    # all binaries to install.
-    mkdir -p $tmpDir
-    cp -r $releaseDir/* $tmpDir/
-    bins=$(find $tmpDir \
-      -maxdepth 1 \
-      -type f \
-      -executable ! \( -regex ".*\.\(so.[0-9.]+\|so\|a\|dylib\)" \))
-  '';
-
   checkPhase = args.checkPhase or (let
     argstr = "${lib.optionalString (checkType == "release") "--release"} --target ${target} --frozen";
     threads = if cargoParallelTestThreads then "$NIX_BUILD_CORES" else "1";
@@ -173,11 +144,19 @@ stdenv.mkDerivation ((removeAttrs args ["depsExtraArgs"]) // lib.optionalAttrs u
 
   strictDeps = true;
 
-  inherit releaseDir tmpDir;
-
   installPhase = args.installPhase or ''
     runHook preInstall
 
+    # This needs to be done after postBuild: packages like `cargo` do a pushd/popd in
+    # the pre/postBuild-hooks that need to be taken into account before gathering
+    # all binaries to install.
+    mkdir -p $tmpDir
+    cp -r $releaseDir/* $tmpDir/
+    bins=$(find $tmpDir \
+      -maxdepth 1 \
+      -type f \
+      -executable ! \( -regex ".*\.\(so.[0-9.]+\|so\|a\|dylib\)" \))
+
     # rename the output dir to a architecture independent one
     mapfile -t targets < <(find "$NIX_BUILD_TOP" -type d | grep '${tmpDir}$')
     for target in "''${targets[@]}"; do
diff --git a/pkgs/build-support/rust/hooks/cargo-build-hook.sh b/pkgs/build-support/rust/hooks/cargo-build-hook.sh
new file mode 100644
index 00000000000..55585233413
--- /dev/null
+++ b/pkgs/build-support/rust/hooks/cargo-build-hook.sh
@@ -0,0 +1,33 @@
+cargoBuildHook() {
+    echo "Executing cargoBuildHook"
+
+    runHook preBuild
+
+    if [ ! -z "${buildAndTestSubdir-}" ]; then
+        pushd "${buildAndTestSubdir}"
+    fi
+
+    (
+    set -x
+    env \
+      "CC_@rustBuildPlatform@=@ccForBuild@" \
+      "CXX_@rustBuildPlatform@=@cxxForBuild@" \
+      "CC_@rustTargetPlatform@=@ccForHost@" \
+      "CXX_@rustTargetPlatform@=@cxxForHost@" \
+      cargo build -j $NIX_BUILD_CORES \
+        --target @rustTargetPlatformSpec@ \
+        --frozen \
+        ${cargoBuildType} \
+        ${cargoBuildFlags}
+    )
+
+    runHook postBuild
+
+    if [ ! -z "${buildAndTestSubdir-}" ]; then
+        popd
+    fi
+
+    echo "Finished cargoBuildHook"
+}
+
+buildPhase=cargoBuildHook
diff --git a/pkgs/build-support/rust/hooks/default.nix b/pkgs/build-support/rust/hooks/default.nix
index dea749f9393..e33d5813a13 100644
--- a/pkgs/build-support/rust/hooks/default.nix
+++ b/pkgs/build-support/rust/hooks/default.nix
@@ -1,5 +1,6 @@
 { buildPackages
 , callPackage
+, cargo
 , diffutils
 , lib
 , makeSetupHook
@@ -16,9 +17,24 @@ let
   shortTarget = if targetIsJSON then
       (lib.removeSuffix ".json" (builtins.baseNameOf "${target}"))
     else target;
-  ccForBuild="${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}cc";
-  ccForHost="${stdenv.cc}/bin/${stdenv.cc.targetPrefix}cc";
+  ccForBuild = "${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}cc";
+  cxxForBuild = "${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}c++";
+  ccForHost = "${stdenv.cc}/bin/${stdenv.cc.targetPrefix}cc";
+  cxxForHost = "${stdenv.cc}/bin/${stdenv.cc.targetPrefix}c++";
+  rustBuildPlatform = rust.toRustTarget stdenv.buildPlatform;
+  rustTargetPlatform = rust.toRustTarget stdenv.hostPlatform;
+  rustTargetPlatformSpec = rust.toRustTargetSpec stdenv.hostPlatform;
 in {
+  cargoBuildHook = callPackage ({ }:
+    makeSetupHook {
+      name = "cargo-build-hook.sh";
+      deps = [ cargo ];
+      substitutions = {
+        inherit ccForBuild ccForHost cxxForBuild cxxForHost
+          rustBuildPlatform rustTargetPlatform rustTargetPlatformSpec;
+      };
+    } ./cargo-build-hook.sh) {};
+
   cargoSetupHook = callPackage ({ }:
     makeSetupHook {
       name = "cargo-setup-hook.sh";