From 3016b811b8bc540952c4f64c5ace6442ac607cc5 Mon Sep 17 00:00:00 2001
From: Evan You <yyx990803@gmail.com>
Date: Thu, 3 Dec 2020 13:22:28 -0500
Subject: [PATCH] build: parallelize multi package builds

---
 scripts/build.js | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/scripts/build.js b/scripts/build.js
index f3a66051..26e287c4 100644
--- a/scripts/build.js
+++ b/scripts/build.js
@@ -50,9 +50,25 @@ async function run() {
 }
 
 async function buildAll(targets) {
-  for (const target of targets) {
-    await build(target)
+  await runParallel(require('os').cpus().length, targets, build)
+}
+
+async function runParallel(maxConcurrency, source, iteratorFn) {
+  const ret = []
+  const executing = []
+  for (const item of source) {
+    const p = Promise.resolve().then(() => iteratorFn(item, source))
+    ret.push(p)
+
+    if (maxConcurrency <= source.length) {
+      const e = p.then(() => executing.splice(executing.indexOf(e), 1))
+      executing.push(e)
+      if (executing.length >= maxConcurrency) {
+        await Promise.race(executing)
+      }
+    }
   }
+  return Promise.all(ret)
 }
 
 async function build(target) {