From 9fe76e49b18854fc6bca7ec772649fcc1305067d Mon Sep 17 00:00:00 2001
From: Noethix55555 <277300782+Noethix55555@users.noreply.github.com>
Date: Tue, 16 Jun 2026 23:18:53 -0400
Subject: [PATCH] fix: split process output on \n instead of os.EOL

NewlineTransformer split stdout/stderr on os.EOL. On Windows that is
\r\n, so output using bare \n line endings was never split into
messages: the data was buffered and dropped, because _flush runs after
the stream's end handler has already resolved the run()/end() callback.
Normal print() worked only because Python's text-mode stdout translates
\n to \r\n on Windows.

Split on /\r?\n/ so both line endings are handled.
---
 index.ts                  |  2 +-
 test/test-python-shell.ts | 24 +++++++++++++++++++++++-
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/index.ts b/index.ts
index 9569354..c2cd304 100644
--- a/index.ts
+++ b/index.ts
@@ -86,7 +86,7 @@ export class NewlineTransformer extends Transform {
   _transform(chunk: any, encoding: string, callback: TransformCallback) {
     let data: string = chunk.toString();
     if (this._lastLineData) data = this._lastLineData + data;
-    const lines = data.split(newline);
+    const lines = data.split(/\r?\n/);
     this._lastLineData = lines.pop();
     lines.forEach(this.push.bind(this));
     callback();
diff --git a/test/test-python-shell.ts b/test/test-python-shell.ts
index 3d5de81..1c886b5 100644
--- a/test/test-python-shell.ts
+++ b/test/test-python-shell.ts
@@ -1,5 +1,5 @@
 import * as should from 'should';
-import { PythonShell } from '..';
+import { PythonShell, NewlineTransformer } from '..';
 import { sep, join } from 'path';
 import { EOL as newline } from 'os';
 import { chdir, cwd } from 'process';
@@ -642,3 +642,25 @@ describe('PythonShell', function () {
     });
   });
 });
+
+describe('NewlineTransformer', function () {
+  function collect(input: Buffer): Promise<string[]> {
+    return new Promise((resolve) => {
+      const t = new NewlineTransformer();
+      t.setEncoding('utf8');
+      const out: string[] = [];
+      t.on('data', (chunk) => out.push(chunk.toString()));
+      t.on('end', () => resolve(out));
+      t.write(input);
+      t.end();
+    });
+  }
+
+  it('splits on \\n regardless of the platform line ending', async function () {
+    (await collect(Buffer.from('hello\nworld\n'))).should.eql(['hello', 'world']);
+  });
+
+  it('splits on \\r\\n', async function () {
+    (await collect(Buffer.from('hello\r\nworld\r\n'))).should.eql(['hello', 'world']);
+  });
+});