From aecca1cdf4428c0ee60eaf9a37e2e0305e5d4d1e Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Tue, 25 Feb 2025 14:27:11 +0100
Subject: [PATCH] On mac, calling fsync on stdout/stderr when not isatty
 returns ENOTSUP (#5430)

---
 docs/project/changelog.md | 2 ++
 src/js/streams.ts         | 6 +++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/docs/project/changelog.md b/docs/project/changelog.md
index 094b23c2172..e5bada3e8c4 100644
--- a/docs/project/changelog.md
+++ b/docs/project/changelog.md
@@ -23,6 +23,8 @@ _Insert Date Here_
 - {{ Fix }} `mountNativeFS` API now correctly propagates the error. {pr}`5434`
 - {{ Fix }} `registerJsModule()` now works with non-extensible JS objects, such
   as ES6 modules. {pr}`5452`
+- {{ Fix }} The Pyodide CLI runner now works correctly on macs when stdout is
+  not a tty. {pr}`5430`
 - {{ Fix }} Since 0.27.1, Pyodide has been broken in iOS because iOS ships
   broken wasm-gc support. Pyodide feature detects whether the runtime supports
   wasm-gc and uses it if it is present. Unfortunately, iOS passes the feature
diff --git a/src/js/streams.ts b/src/js/streams.ts
index 439bbc1cf68..12daeb36604 100644
--- a/src/js/streams.ts
+++ b/src/js/streams.ts
@@ -9,7 +9,11 @@ function nodeFsync(fd: number): void {
   try {
     fs.fsyncSync(fd);
   } catch (e: any) {
-    if (e && e.code === "EINVAL") {
+    if (e?.code === "EINVAL") {
+      return;
+    }
+    // On mac, calling fsync on stdout/stderr when not isatty returns ENOTSUP
+    if (e?.code === "ENOTSUP" && (fd === 1 || fd === 2)) {
       return;
     }
     throw e;