From 09fc33171b408a4ab426df4ae70f0d080dc0a52d Mon Sep 17 00:00:00 2001
From: Daijiro Wachi <daijiro.wachi@gmail.com>
Date: Thu, 25 Jun 2026 00:51:29 +0900
Subject: [PATCH] buffer: normalize lone "\r" in Blob native line endings

`new Blob(parts, { endings: 'native' })` failed to normalize a
standalone carriage return. The replacement regex only matched
`\n` and `\r\n`, so a lone `\r` (and runs such as `\r\r`) were
left untouched instead of being converted to the platform's
native line ending.

The WHATWG "convert line endings to native" algorithm requires
`\r`, `\n`, and `\r\n` to all be normalized. Match `\r\n` before
a lone `\r` so that CRLF collapses to a single native ending.

Refs: https://w3c.github.io/FileAPI/#convert-line-endings-to-native

Signed-off-by: Daijiro Wachi <daijiro.wachi@gmail.com>
---
 lib/internal/blob.js       |  2 +-
 test/parallel/test-blob.js | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/lib/internal/blob.js b/lib/internal/blob.js
index dfaa24b79db5ab..fca2813b96a578 100644
--- a/lib/internal/blob.js
+++ b/lib/internal/blob.js
@@ -122,7 +122,7 @@ function getSource(source, endings) {
     source = new Uint8Array(source);
   } else if (!isArrayBufferView(source)) {
     if (endings === 'native')
-      source = RegExpPrototypeSymbolReplace(/\n|\r\n/g, source, EOL);
+      source = RegExpPrototypeSymbolReplace(/\r\n|\r|\n/g, source, EOL);
     source = enc.encode(source);
   }
 
diff --git a/test/parallel/test-blob.js b/test/parallel/test-blob.js
index 19ca24b0319f13..b061fa944f3cec 100644
--- a/test/parallel/test-blob.js
+++ b/test/parallel/test-blob.js
@@ -403,6 +403,24 @@ assert.throws(() => new Blob({}), {
   const b = new Blob(['hello\n'], { endings: 'native' });
   assert.strictEqual(b.size, EOL.length + 5);
 
+  // The WHATWG "convert line endings to native" algorithm normalizes every
+  // standalone "\r", "\n", and "\r\n" sequence to the native line ending.
+  // Refs: https://w3c.github.io/FileAPI/#convert-line-endings-to-native
+  (async () => {
+    const cases = [
+      ['a\rb', `a${EOL}b`],
+      ['a\nb', `a${EOL}b`],
+      ['a\r\nb', `a${EOL}b`],
+      ['a\r\rb', `a${EOL}${EOL}b`],
+      ['a\n\rb', `a${EOL}${EOL}b`],
+      ['\r\n\r', `${EOL}${EOL}`],
+    ];
+    for (const [input, expected] of cases) {
+      const blob = new Blob([input], { endings: 'native' });
+      assert.strictEqual(await blob.text(), expected);
+    }
+  })().then(common.mustCall());
+
   [1, {}, 'foo'].forEach((endings) => {
     assert.throws(() => new Blob([], { endings }), {
       code: 'ERR_INVALID_ARG_VALUE',