fix: expose npm binary in toolchain files

Fixes #3844

Author: alexeagle

e2e/smoke/BUILD.bazel

@@ -184,6 +184,14 @@ diff_test(
     target_compatible_with = not_windows,
 )
 
+genrule(
+    name = "npm_help",
+    outs = ["help.txt"],
+    cmd = "$(NPM_PATH) --help > $@ || true",
+    toolchains = ["@nodejs_toolchains//:resolved_toolchain"],
+    tools = ["@nodejs_toolchains//:resolved_toolchain"],
+)
+
 ################################################
 # Tests and setup for the toolchain changes
 

nodejs/toolchain.bzl

@@ -83,9 +83,10 @@ def _nodejs_toolchain_impl(ctx):
         "NODE_PATH": ctx.file.node.path if ctx.attr.node else ctx.attr.node_path,
         "NPM_PATH": ctx.file.npm.path if ctx.attr.npm else ctx.attr.npm_path,
     })
+    files = [f for f in [ctx.file.node, ctx.file.npm] if f]
     default = DefaultInfo(
-        files = depset([ctx.file.node]) if ctx.attr.node else depset(),
-        runfiles = ctx.runfiles(files = [ctx.file.node] if ctx.attr.node else []),
+        files = depset(files),
+        runfiles = ctx.runfiles(files = files),
     )
     npm_sources = depset([ctx.file.npm] + ctx.files.npm_srcs)
     nodeinfo = NodeInfo(