Rebuilding native modules for Linux

example.bzl

package_node_modules_cmd = """
    mkdir -p "$@"
    cp -pRL "external/npm/node_modules" "$(@D)"
    """

rebuild_node_modules_cmd = """
    NPM="$$(pwd)/$(location @nodejs//:bin/npm)"
    (
        cd "$(@D)"

        # Remove known-bad dependencies.
        rm -rf node_modules/fsevents

        # Fetch native module binaries for Linux. We're explicitly setting
        # --fallback-to-build=false so that we never build from source.
        # If we build from source on macOS, we will get a macOS binary,
        # which we don't want.
        $$NPM rebuild \
            --update-binary \
            --target_arch=x64 \
            --target_platform=linux \
            --target_libc=glibc \
            --fallback-to-build=false
    ) > "$(@D)/npm.log"
    """

native.genrule(
    name = "node_modules-rebuilt",
    message = "Packaging node_modules for Linux",
    srcs = [],
    tools = [
        "@nodejs//:bin/npm",
        "@npm//:node_modules",
    ],
    outs = ["node_modules"],

    tags = ["local"],  # run without sandboxing for ~2x speedup on macOS

    cmd = select({
        "@bazel_tools//src/conditions:darwin": (
            package_node_modules_cmd + rebuild_node_modules_cmd
        ),
        "//conditions:default": package_node_modules_cmd,
    }),
)