From 25ccf401502705e97f0fbd6a033c5763c249ebca Mon Sep 17 00:00:00 2001
From: Lily Foster <lily@lily.flowers>
Date: Thu, 29 Jun 2023 09:46:33 -0400
Subject: [PATCH] prefetch-npm-deps: support NIX_BUILD_CORES

(cherry picked from commit 9af0383296227450889a6d41107d892c29eb0c21)
---
 pkgs/build-support/node/fetch-npm-deps/src/main.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/pkgs/build-support/node/fetch-npm-deps/src/main.rs b/pkgs/build-support/node/fetch-npm-deps/src/main.rs
index e6e44fc9d92e..d664cfca4a14 100644
--- a/pkgs/build-support/node/fetch-npm-deps/src/main.rs
+++ b/pkgs/build-support/node/fetch-npm-deps/src/main.rs
@@ -182,6 +182,18 @@ fn main() -> anyhow::Result<()> {
         process::exit(1);
     }
 
+    if let Ok(jobs) = env::var("NIX_BUILD_CORES") {
+        if !jobs.is_empty() {
+            rayon::ThreadPoolBuilder::new()
+                .num_threads(
+                    jobs.parse()
+                        .expect("NIX_BUILD_CORES must be a whole number"),
+                )
+                .build_global()
+                .unwrap();
+        }
+    }
+
     if args[1] == "--fixup-lockfile" {
         let lock = serde_json::from_str(&fs::read_to_string(&args[2])?)?;