Add install_tools option to yarn_modules rule (#60)

node/internal/yarn_modules.bzl

@@ -55,10 +55,17 @@ def _yarn_modules_impl(ctx):
     execute(ctx, ["cp", parse_yarn_lock_js, "internal/parse_yarn_lock.js"])
     execute(ctx, ["cp", yarn_js, "yarn.js"])
 
+    install_path = [node.dirname]
+    for tool in ctx.attr.install_tools:
+        tool_path = ctx.which(tool)
+        if not tool_path:
+            fail("Required install tool '%s' is not in the PATH" % tool, "install_tools")
+        install_path.append(tool_path.dirname)
+    install_path.append("$PATH")
+
     # Build node_modules via 'yarn install'
     execute(ctx, [node, yarn_js, "install"], quiet = True, environment = {
-        # postinstall scripts may need to find the node binary
-        "PATH": "%s:$PATH" % ctx.path(node).dirname,
+        "PATH": ":".join(install_path),
     })
 
     # Run the script and save the stdout to our BUILD file(s)
@@ -93,6 +100,9 @@ yarn_modules = repository_rule(
             default = Label("@yarn//:bin/yarn.js"),
             single_file = True,
         ),
+        # If specififed, augment the PATH environment variable with these
+        # tools during 'yarn install'.  
+        "install_tools": attr.string_list(),
         "package_json": attr.label(
             mandatory = False,
             allow_files = FileType(["package.json"]),

tests/node-ref/BUILD

@@ -0,0 +1,19 @@
+package(default_visibility = ["//visibility:public"])
+
+load("@org_pubref_rules_node//node:rules.bzl", "node_binary")
+
+node_binary(
+    name = "example",
+    main = "example.js",
+    deps = [
+        "@yarn_modules//:_all_",
+    ],
+)
+
+sh_test(
+    name = "example_test",
+    size = "small",
+    srcs = ["example_test.sh"],
+    data = [":example"],
+)
+

tests/node-ref/README.md

@@ -0,0 +1,9 @@
+# Ref Example
+
+This example demonstrates the `install_tools` option.
+
+In this case, `yarn install` of the `ref` package triggers `node-gyp`,
+which in this case uses tools in `/bin` and `/usr/bin`.  We normally
+take these for granted as being on the path but bazel runs the yarn
+install script in the bare environment, so we need to specify these
+explicitly to build up the appropriate `PATH`.

tests/node-ref/WORKSPACE

@@ -0,0 +1,22 @@
+local_repository(
+    name = "org_pubref_rules_node",
+    path = "../..",
+)
+
+load("@org_pubref_rules_node//node:rules.bzl", "node_repositories", "yarn_modules")
+
+node_repositories()
+
+yarn_modules(
+    name = "yarn_modules",
+    deps = {
+        "ref": "1.3.5",
+    },
+    # yarn install of 'ref' triggers node-gyp. This will in turn
+    # require 'sh' and 'dirname'.  Explicitly make these tools
+    # available during the yarn install step.
+    install_tools = [
+        "sh", # /bin
+        "dirname", # #/usr/bin
+    ],
+)

tests/node-ref/example.js

@@ -0,0 +1,9 @@
+const ref = require("ref");
+
+const buf = new Buffer(4)
+
+buf.writeInt32LE(12345, 0)
+buf.type = ref.types.int
+
+console.log(buf.deref())  // ← 12345
+

tests/node-ref/example_test.sh

@@ -0,0 +1,7 @@
+set -e
+
+if (./example &) | grep -q '12345'; then
+    echo "PASS"
+else
+    exit 1
+fi