allow specifying the binary directory when making node_modules

prelude-nri/node.bzl

@@ -4,13 +4,16 @@ load("@prelude//python:toolchain.bzl", "PythonToolchainInfo")
 def _node_modules_impl(ctx: "context") -> [DefaultInfo.type]:
     out = ctx.actions.declare_output("node_modules")
 
+    node_toolchain = ctx.attrs._node_toolchain[NodeToolchainInfo]
+
     ctx.actions.run(
         [
             ctx.attrs._python_toolchain[PythonToolchainInfo].interpreter,
-            ctx.attrs._node_toolchain[NodeToolchainInfo].build_node_modules[DefaultInfo].default_outputs,
+            node_toolchain.build_node_modules[DefaultInfo].default_outputs,
             out.as_output(),
             "--package", ctx.attrs.package,
             "--package-lock", ctx.attrs.package_lock,
+            "--bin-dir", node_toolchain.bin_dir[DefaultInfo].default_outputs,
         ],
         category = "npm",
     )

prelude-nri/node/build_node_modules.py

@@ -1,10 +1,6 @@
 #!/usr/bin/env python3
 """
 Make a fresh `node_modules` directory in an isolated directory.
-
-This script assumes it has `npm` and its dependencies in the right `PATH` and
-`NODE_PATH`. Make sure that's set up properly using whatever installation method
-is necessary!
 """
 import argparse
 import os
@@ -31,9 +27,18 @@ if __name__ == "__main__":
         action="store_true",
         help="Don't run package post-install scripts",
     )
+    parser.add_argument(
+        "--bin-dir",
+        help="Path to a node installation's binary directory. If present, will be treated as an extra entry in PATH for the duration of this command.",
+    )
 
     args = parser.parse_args()
 
+    if args.bin_dir:
+        os.environ["PATH"] = "{}:{}".format(
+            os.path.abspath(args.bin_dir), os.environ["PATH"]
+        )
+
     with tempfile.TemporaryDirectory() as tempdir:
         # npm wants these to be real files for whatever reason, and will throw
         # errors if they're symlinks.

prelude-nri/node/toolchain.bzl

@@ -1,5 +1,5 @@
 NodeToolchainInfo = provider(fields=[
-    "bin",
+    "bin_dir",
     "node",
     "build_node_modules",
 ])
@@ -12,7 +12,7 @@ def _node_toolchain_impl(ctx) -> [[DefaultInfo.type, NodeToolchainInfo.type]]:
     return [
         DefaultInfo(),
         NodeToolchainInfo(
-            bin = ctx.attrs.bin[DefaultInfo].default_outputs,
+            bin_dir = ctx.attrs.bin_dir,
             node = ctx.attrs.node[RunInfo],
             build_node_modules = ctx.attrs._build_node_modules,
         ),
@@ -21,7 +21,7 @@ def _node_toolchain_impl(ctx) -> [[DefaultInfo.type, NodeToolchainInfo.type]]:
 node_toolchain = rule(
     impl = _node_toolchain_impl,
     attrs = {
-        "bin": attrs.dep(
+        "bin_dir": attrs.dep(
             default="prelude-nri//node:bin"
         ),
         "node": attrs.dep(