add a script to build an isolated node_modules

prelude-nri/node/BUCK

@@ -34,3 +34,8 @@ genrule(
     visibility = ["PUBLIC"],
     executable = True,
 )
+
+export_file(
+    name = "build_node_modules.py",
+    visibility = ["PUBLIC"],
+)

prelude-nri/node/build_node_modules.py

@@ -0,0 +1,56 @@
+#!/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
+import subprocess
+import sys
+import shutil
+import tempfile
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("out", help="Where you want node_modules to end up")
+    parser.add_argument(
+        "--package",
+        help="The package.json to install dependencies from",
+        default="package.json",
+    )
+    parser.add_argument(
+        "--package-lock",
+        help="The package-lock.json corresponding to package.json",
+        default="package-lock.json",
+    )
+    parser.add_argument(
+        "--no-ignore-scripts",
+        action="store_true",
+        help="Don't run package post-install scripts",
+    )
+
+    args = parser.parse_args()
+
+    with tempfile.TemporaryDirectory() as tempdir:
+        # npm wants these to be real files for whatever reason, and will throw
+        # errors if they're symlinks.
+        shutil.copy(args.package, os.path.join(tempdir, "package.json"))
+        shutil.copy(args.package_lock, os.path.join(tempdir, "package-lock.json"))
+
+        cmd = ["npm", "clean-install"]
+        if not args.no_ignore_scripts:
+            cmd.append("--ignore-scripts")
+
+        proc = subprocess.Popen(cmd, cwd=tempdir)
+        proc.communicate()
+
+        if proc.returncode == 0:
+            os.rename(
+                os.path.join(tempdir, "node_modules"),
+                args.out,
+            )
+
+    sys.exit(proc.returncode)

prelude-nri/node/toolchain.bzl

@@ -1,6 +1,7 @@
 NodeToolchainInfo = provider(fields=[
     "bin",
     "node",
+    "build_node_modules",
 ])
 
 def _node_toolchain_impl(ctx) -> [[DefaultInfo.type, NodeToolchainInfo.type]]:
@@ -13,6 +14,7 @@ def _node_toolchain_impl(ctx) -> [[DefaultInfo.type, NodeToolchainInfo.type]]:
         NodeToolchainInfo(
             bin = ctx.attrs.bin[DefaultInfo].default_outputs,
             node = ctx.attrs.node[RunInfo],
+            build_node_modules = ctx.attrs._build_node_modules,
         ),
     ]
 
@@ -26,6 +28,9 @@ node_toolchain = rule(
             providers = [RunInfo],
             default="prelude-nri//node:node"
         ),
+        "_build_node_modules": attrs.dep(
+            default="prelude-nri//node:build_node_modules.py",
+        ),
     },
     is_toolchain_rule = True,
 )