Support nixpkgs_node_configure

[epigramengineer]

Is your feature request related to a problem? Please describe.
using rules_node with the nixpkgs node is extremely painful and requires the workaround specified in bazel-contrib/rules_nodejs#464 / bazelbuild/bazel#2927

Specifically:

nixpkgs_package(
    name = "nixpkgs_nodejs",
    build_file_content = 'exports_files(glob(["nixpkgs_nodejs/**"]))',
    nix_file_content = """
    with import <nixpkgs> { config = {}; overlays = []; };
    runCommand "nodejs-build" { buildInputs = [ nodejs ]; } ''
      mkdir -p $out/nixpkgs_nodejs
      cd $out/nixpkgs_nodejs
      for i in ${nodejs}/*; do ln -s $i; done
      ''
    """,
    nixopts = [
        "--option",
        "sandbox",
        "false",
    ],
    repository = "@nixpkgs",
)

load("@build_bazel_rules_nodejs//:index.bzl", "node_repositories")
node_repositories(
  vendored_node = "@nixpkgs_nodejs",
  package_json = [":package.json"],
)

Describe the solution you'd like
Ideally this is a solved with a call to nixpkgs_node_configure

Describe alternatives you've considered
^ workaround described above

Additional context
bazel-contrib/rules_nodejs#464
bazelbuild/bazel#2927

[aherrmann]

This would be great to have. With more recent versions of rules_nodejs the following setup works.

http_archive(
    name = "build_bazel_rules_nodejs",
    sha256 = "cfc289523cf1594598215901154a6c2515e8bf3671fd708264a6f6aefe02bf39",
    urls = ["https://github.com/bazelbuild/rules_nodejs/releases/download/4.4.6/rules_nodejs-4.4.6.tar.gz"],
)

nixpkgs_package(
    name = "nix_node",
    build_file_content = 'exports_files(glob(["nix_node/bin/**"]))',
    nix_file_content = 'with import <nixpkgs> {}; linkFarm "nodejs" [ { name = "nix_node"; path = nodejs-10_x; }]',
    repository = "@nixpkgs",
)

load("@build_bazel_rules_nodejs//:index.bzl", "node_repositories")

node_repositories(
    package_json = ["//typescript:package.json"],
    vendored_node = "@nix_node",
)

Having a nixpkgs_node_configure that captures that would still be great.

PRs to add this are welcome.

This should go into a separate file here or a dedicated component after #182 to not introduce a dependency on rules_nodejs to all users of rules_nixpkgs independent of whether they use this or not.

A test case would also be good. See here for a Go example.

[benradf]

I started looking into this but it seems like node_repositories changed quite drastically between 4.4.6 and 5.5.3. It no longer takes package_json and vendored_node parameters. I don't really have the knowledge needed to investigate this further so I'm going to unassign myself for now.