buildRustCrate: move common build functions to a dedicated file

This means we aren't rebuilding hat file for each crate we are building
and the buildPhase expression is a lot easier to comprehent.

2 files changed, 155 insertions, 101 deletions

diff --git a/pkgs/build-support/rust/build-rust-crate/build-crate.nix b/pkgs/build-support/rust/build-rust-crate/build-crate.nix
index 70bd84c8346..9f1930fa62b 100644
--- a/pkgs/build-support/rust/build-rust-crate/build-crate.nix
+++ b/pkgs/build-support/rust/build-rust-crate/build-crate.nix
@@ -3,128 +3,65 @@
   dependencies,
   crateFeatures, crateRenames, libName, release, libPath,
   crateType, metadata, crateBin, hasCrateBin,
-  extraRustcOpts, verbose, colors }:
+  extraRustcOpts, verbose, colors,
+}:
 
   let
-    deps = mkRustcDepArgs dependencies crateRenames;
-    rustcOpts =
-      lib.foldl' (opts: opt: opts + " " + opt)
-        (if release then "-C opt-level=3" else "-C debuginfo=2")
-        (["-C codegen-units=$NIX_BUILD_CORES"] ++ extraRustcOpts);
+    baseRustcOpts =
+      [(if release then "-C opt-level=3" else "-C debuginfo=2")]
+      ++ ["-C codegen-units=$NIX_BUILD_CORES"]
+      ++ [(mkRustcDepArgs dependencies crateRenames)]
+      ++ [crateFeatures]
+      ++ extraRustcOpts
+      ++ lib.optional (stdenv.hostPlatform != stdenv.buildPlatform) "--target ${rust.toRustTarget stdenv.hostPlatform} -C linker=${stdenv.hostPlatform.config}-gcc"
+    ;
     rustcMeta = "-C metadata=${metadata} -C extra-filename=-${metadata}";
-  in ''
-    runHook preBuild
-    ${echo_build_heading colors}
-    ${noisily colors verbose}
 
-    build_lib() {
-       lib_src=$1
-       echo_build_heading $lib_src ${libName}
 
-       noisily rustc --crate-name $CRATE_NAME $lib_src \
-         ${lib.strings.concatStrings (map (x: " --crate-type ${x}") crateType)}  \
-         ${rustcOpts} ${rustcMeta} ${crateFeatures} --out-dir target/lib \
-         --emit=dep-info,link -L dependency=target/deps ${deps} --cap-lints allow \
-         $BUILD_OUT_DIR $EXTRA_BUILD $EXTRA_FEATURES --color ${colors}
+    # build the final rustc arguments that can be different between different
+    # crates
+    libRustcOpts = lib.concatStringsSep " " (
+      baseRustcOpts
+      ++ [rustcMeta]
+      ++ (map (x: "--crate-type ${x}") crateType)
+    );
 
-       EXTRA_LIB=" --extern $CRATE_NAME=target/lib/lib$CRATE_NAME-${metadata}.rlib"
-       if [ -e target/deps/lib$CRATE_NAME-${metadata}${stdenv.hostPlatform.extensions.sharedLibrary} ]; then
-          EXTRA_LIB="$EXTRA_LIB --extern $CRATE_NAME=target/lib/lib$CRATE_NAME-${metadata}${stdenv.hostPlatform.extensions.sharedLibrary}"
-       fi
-    }
+    binRustcOpts = lib.concatStringsSep " " (
+      baseRustcOpts
+    );
 
-    build_bin() {
-      crate_name=$1
-      crate_name_=$(echo $crate_name | tr '-' '_')
-      main_file=""
-      if [[ ! -z $2 ]]; then
-        main_file=$2
-      fi
-      echo_build_heading $@
-      noisily rustc --crate-name $crate_name_ $main_file --crate-type bin ${rustcOpts}\
-        ${crateFeatures} --out-dir target/bin --emit=dep-info,link -L dependency=target/deps \
-        $LINK ${deps}$EXTRA_LIB --cap-lints allow \
-        $BUILD_OUT_DIR $EXTRA_BUILD $EXTRA_FEATURES --color ${colors} \
-        ${if stdenv.hostPlatform != stdenv.buildPlatform then "--target ${rust.toRustTarget stdenv.hostPlatform} -C linker=${stdenv.hostPlatform.config}-gcc" else ""}
-      if [ "$crate_name_" != "$crate_name" ]; then
-        mv target/bin/$crate_name_ target/bin/$crate_name
-      fi
-    }
+  in ''
+    runHook preBuild
+    ${echo_build_heading colors}
+    ${noisily colors verbose}
 
+    # configure & source common build functions
+    LIB_RUSTC_OPTS="${libRustcOpts}"
+    BIN_RUSTC_OPTS="${binRustcOpts}"
+    LIB_EXT="${stdenv.hostPlatform.extensions.sharedLibrary}"
+    LIB_PATH="${libPath}"
+    LIB_NAME="${libName}"
+    source ${./lib.sh}
 
-    EXTRA_LIB=""
     CRATE_NAME='${lib.replaceStrings ["-"] ["_"] libName}'
 
-    if [[ -e target/link_ ]]; then
-      EXTRA_BUILD="$(cat target/link_) $EXTRA_BUILD"
-    fi
+    setup_link_paths
 
-    if [[ -e "${libPath}" ]]; then
-       build_lib ${libPath}
+    if [[ -e "$LIB_PATH" ]]; then
+       build_lib $LIB_PATH
     elif [[ -e src/lib.rs ]]; then
        build_lib src/lib.rs
-    elif [[ -e src/${libName}.rs ]]; then
-       build_lib src/${libName}.rs
+    elif [[ -e "src/$LIB_NAME.rs" ]]; then
+       build_lib src/$LIB_NAME.rs
     fi
 
-    echo "$EXTRA_LINK_SEARCH" | while read i; do
-       if [[ ! -z "$i" ]]; then
-         for library in $i; do
-           echo "-L $library" >> target/link
-           L=$(echo $library | sed -e "s#$(pwd)/target/build#$lib/lib#")
-           echo "-L $L" >> target/link.final
-         done
-       fi
-    done
-    echo "$EXTRA_LINK" | while read i; do
-       if [[ ! -z "$i" ]]; then
-         for library in $i; do
-           echo "-l $library" >> target/link
-           echo "-l $library" >> target/link.final
-         done
-       fi
-    done
-
-    if [[ -e target/link ]]; then
-       sort -u target/link.final > target/link.final.sorted
-       mv target/link.final.sorted target/link.final
-       sort -u target/link > target/link.sorted
-       mv target/link.sorted target/link
-
-       tr '\n' ' ' < target/link > target/link_
-       LINK=$(cat target/link_)
-    fi
 
     ${lib.optionalString (lib.length crateBin > 0) (lib.concatMapStringsSep "\n" (bin: ''
       mkdir -p target/bin
       BIN_NAME='${bin.name or crateName}'
       ${if !bin ? path then ''
-        # heuristic to "guess" the correct source file as found in cargo:
-        # https://github.com/rust-lang/cargo/blob/90fc9f620190d5fa3c80b0c8c65a1e1361e6b8ae/src/cargo/util/toml/targets.rs#L308-L325
-
-        # the first two cases are the "new" default IIRC
-        BIN_NAME_='${lib.replaceStrings ["-"] ["_"] bin.name}'
-        FILES=( "src/bin/$BIN_NAME.rs" "src/bin/$BIN_NAME/main.rs" "src/bin/$BIN_NAME_.rs" "src/bin/$BIN_NAME_/main.rs" "src/bin/main.rs" "src/main.rs" )
-
-        if ! [ -e "${libPath}" -o -e src/lib.rs -o -e "src/${libName}.rs" ]; then
-          # if this is not a library the following path is also valid
-          FILES=( "src/$BIN_NAME.rs" "src/$BIN_NAME_.rs" "''${FILES[@]}" )
-        fi
-
-        for file in "''${FILES[@]}";
-        do
-          echo "checking file $file"
-          # first file that exists wins
-          if [[ -e "$file" ]]; then
-                  BIN_PATH="$file"
-                  break
-          fi
-        done
-
-        if [[ -z "$BIN_PATH" ]]; then
-          echo "failed to find file for binary target: $BIN_NAME" >&2
-          exit 1
-        fi
+        BIN_PATH=""
+        search_for_bin_path "$BIN_NAME"
       '' else ''
         BIN_PATH='${bin.path}'
       ''}
diff --git a/pkgs/build-support/rust/build-rust-crate/lib.sh b/pkgs/build-support/rust/build-rust-crate/lib.sh
new file mode 100644
index 00000000000..24c712468ea
--- /dev/null
+++ b/pkgs/build-support/rust/build-rust-crate/lib.sh
@@ -0,0 +1,117 @@
+build_lib() {
+  lib_src=$1
+  echo_build_heading $lib_src ${libName}
+
+  noisily rustc \
+    --crate-name $CRATE_NAME \
+    $lib_src \
+    --out-dir target/lib \
+    --emit=dep-info,link \
+    -L dependency=target/deps \
+    --cap-lints allow \
+    $LIB_RUSTC_OPTS \
+    $BUILD_OUT_DIR \
+    $EXTRA_BUILD \
+    $EXTRA_FEATURES \
+    --color $colors
+
+  EXTRA_LIB=" --extern $CRATE_NAME=target/lib/lib$CRATE_NAME-$metadata.rlib"
+  if [ -e target/deps/lib$CRATE_NAME-$metadata$LIB_EXT ]; then
+     EXTRA_LIB="$EXTRA_LIB --extern $CRATE_NAME=target/lib/lib$CRATE_NAME-$metadata$LIB_EXT"
+  fi
+}
+
+build_bin() {
+  crate_name=$1
+  crate_name_=$(echo $crate_name | tr '-' '_')
+  main_file=""
+  if [[ ! -z $2 ]]; then
+    main_file=$2
+  fi
+  echo_build_heading $@
+  noisily rustc \
+    --crate-name $crate_name_ \
+    $main_file \
+    --crate-type bin \
+    $BIN_RUSTC_OPTS \
+    --out-dir target/bin \
+    --emit=dep-info,link \
+    -L dependency=target/deps \
+    $LINK \
+    $EXTRA_LIB \
+    --cap-lints allow \
+    $BUILD_OUT_DIR \
+    $EXTRA_BUILD \
+    $EXTRA_FEATURES \
+    --color ${colors} \
+
+  if [ "$crate_name_" != "$crate_name" ]; then
+    mv target/bin/$crate_name_ target/bin/$crate_name
+  fi
+}
+
+setup_link_paths() {
+  EXTRA_LIB=""
+  if [[ -e target/link_ ]]; then
+    EXTRA_BUILD="$(cat target/link_) $EXTRA_BUILD"
+  fi
+
+  echo "$EXTRA_LINK_SEARCH" | while read i; do
+     if [[ ! -z "$i" ]]; then
+       for library in $i; do
+         echo "-L $library" >> target/link
+         L=$(echo $library | sed -e "s#$(pwd)/target/build#$lib/lib#")
+         echo "-L $L" >> target/link.final
+       done
+     fi
+  done
+  echo "$EXTRA_LINK" | while read i; do
+     if [[ ! -z "$i" ]]; then
+       for library in $i; do
+         echo "-l $library" >> target/link
+         echo "-l $library" >> target/link.final
+       done
+     fi
+  done
+
+  if [[ -e target/link ]]; then
+     sort -u target/link.final > target/link.final.sorted
+     mv target/link.final.sorted target/link.final
+     sort -u target/link > target/link.sorted
+     mv target/link.sorted target/link
+
+     tr '\n' ' ' < target/link > target/link_
+     LINK=$(cat target/link_)
+  fi
+}
+
+search_for_bin_path() {
+  # heuristic to "guess" the correct source file as found in cargo:
+  # https://github.com/rust-lang/cargo/blob/90fc9f620190d5fa3c80b0c8c65a1e1361e6b8ae/src/cargo/util/toml/targets.rs#L308-L325
+
+  BIN_NAME=$1
+  BIN_NAME_=$(echo $BIN_NAME | tr '-' '_')
+
+  # the first two cases are the "new" default IIRC
+  FILES=( "src/bin/$BIN_NAME.rs" "src/bin/$BIN_NAME/main.rs" "src/bin/$BIN_NAME_.rs" "src/bin/$BIN_NAME_/main.rs" "src/bin/main.rs" "src/main.rs" )
+
+  if ! [ -e "$LIB_PATH" -o -e src/lib.rs -o -e "src/$LIB_NAME.rs" ]; then
+    # if this is not a library the following path is also valid
+    FILES=( "src/$BIN_NAME.rs" "src/$BIN_NAME_.rs" "${FILES[@]}" )
+  fi
+
+  for file in "${FILES[@]}";
+  do
+    echo "checking file $file"
+    # first file that exists wins
+    if [[ -e "$file" ]]; then
+            BIN_PATH="$file"
+            break
+    fi
+  done
+
+  if [[ -z "$BIN_PATH" ]]; then
+    echo "failed to find file for binary target: $BIN_NAME" >&2
+    exit 1
+  fi
+}