build-crate.nix

{ lib, stdenv
, mkRustcDepArgs, mkRustcFeatureArgs, needUnstableCLI, rustc
}:

{ crateName,
  dependencies,
  crateFeatures, crateRenames, libName, release, libPath,
  crateType, metadata, crateBin, hasCrateBin,
  extraRustcOpts, verbose, colors,
  buildTests,
  codegenUnits
}:

  let
    baseRustcOpts =
      [
        (if release then "-C opt-level=3" else "-C debuginfo=2")
        "-C codegen-units=${toString codegenUnits}"
        "--remap-path-prefix=$NIX_BUILD_TOP=/"
        (mkRustcDepArgs dependencies crateRenames)
        (mkRustcFeatureArgs crateFeatures)
      ] ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
        "--target" stdenv.hostPlatform.rust.rustcTargetSpec
      ] ++ lib.optionals (needUnstableCLI dependencies) [
        "-Z" "unstable-options"
      ] ++ extraRustcOpts
      # since rustc 1.42 the "proc_macro" crate is part of the default crate prelude
      # https://github.com/rust-lang/cargo/commit/4d64eb99a4#diff-7f98585dbf9d30aa100c8318e2c77e79R1021-R1022
      ++ lib.optional (lib.elem "proc-macro" crateType) "--extern proc_macro"
      ++ lib.optional (stdenv.hostPlatform.linker == "lld") # Needed when building for targets that use lld. e.g. 'wasm32-unknown-unknown'
        "-C linker=${rustc.llvmPackages.lld}/bin/lld"
      ++ lib.optional (stdenv.hasCC && stdenv.hostPlatform.linker != "lld")
        "-C linker=${stdenv.cc}/bin/${stdenv.cc.targetPrefix}cc"
    ;
    rustcMeta = "-C metadata=${metadata} -C extra-filename=-${metadata}";


    # build the final rustc arguments that can be different between different
    # crates
    libRustcOpts = lib.concatStringsSep " " (
      baseRustcOpts
      ++ [rustcMeta]
      ++ (map (x: "--crate-type ${x}") crateType)
    );

    binRustcOpts = lib.concatStringsSep " " baseRustcOpts;

    build_bin = if buildTests then "build_bin_test" else "build_bin";
  in ''
    runHook preBuild

    # configure & source common build functions
    LIB_RUSTC_OPTS="${libRustcOpts}"
    BIN_RUSTC_OPTS="${binRustcOpts}"
    LIB_EXT="${stdenv.hostPlatform.extensions.library}"
    LIB_PATH="${libPath}"
    LIB_NAME="${libName}"

    CRATE_NAME='${lib.replaceStrings ["-"] ["_"] libName}'

    setup_link_paths

    if [[ -e "$LIB_PATH" ]]; then
       build_lib "$LIB_PATH"
       ${lib.optionalString buildTests ''build_lib_test "$LIB_PATH"''}
    elif [[ -e src/lib.rs ]]; then
       build_lib src/lib.rs
       ${lib.optionalString buildTests "build_lib_test src/lib.rs"}
    fi



    ${lib.optionalString (lib.length crateBin > 0) (lib.concatMapStringsSep "\n" (bin:
    let
      haveRequiredFeature = if bin ? requiredFeatures then
        # Check that all element in requiredFeatures are also present in crateFeatures
        lib.intersectLists bin.requiredFeatures crateFeatures == bin.requiredFeatures
      else
        true;
    in
    if haveRequiredFeature then ''
      mkdir -p target/bin
      BIN_NAME='${bin.name or crateName}'
      ${if !bin ? path then ''
        BIN_PATH=""
        search_for_bin_path "$BIN_NAME"
      '' else ''
        BIN_PATH='${bin.path}'
      ''}
        ${build_bin} "$BIN_NAME" "$BIN_PATH"
    '' else ''
      echo Binary ${bin.name or crateName} not compiled due to not having all of the required features -- ${lib.escapeShellArg (builtins.toJSON bin.requiredFeatures)} -- enabled.
    '') crateBin)}

    ${lib.optionalString buildTests ''
    # When tests are enabled build all the files in the `tests` directory as
    # test binaries.
    if [ -d tests ]; then
      # find all the .rs files (or symlinks to those) in the tests directory, no subdirectories
      find tests -maxdepth 1 \( -type f -o -type l \) -a -name '*.rs' -print0 | while IFS= read -r -d ''' file; do
        mkdir -p target/bin
        build_bin_test_file "$file"
      done

      # find all the subdirectories of tests/ that contain a main.rs file as
      # that is also a test according to cargo
      find tests/ -mindepth 1 -maxdepth 2 \( -type f -o -type l \) -a -name 'main.rs' -print0 | while IFS= read -r -d ''' file; do
        mkdir -p target/bin
        build_bin_test_file "$file"
      done

    fi
    ''}

    # If crateBin is empty and hasCrateBin is not set then we must try to
    # detect some kind of bin target based on some files that might exist.
    ${lib.optionalString (lib.length crateBin == 0 && !hasCrateBin) ''
      if [[ -e src/main.rs ]]; then
        mkdir -p target/bin
        ${build_bin} ${crateName} src/main.rs
      fi
      for i in src/bin/*.rs; do #*/
        mkdir -p target/bin
        ${build_bin} "$(basename $i .rs)" "$i"
      done
    ''}
    # Remove object files to avoid "wrong ELF type"
    find target -type f -name "*.o" -print0 | xargs -0 rm -f
    runHook postBuild
  ''