From 7e2a3d1b3ec1cf0b9a1f1a9aa1d6c81c621ff095 Mon Sep 17 00:00:00 2001
From: Charlotte Som <charlotte@som.codes>
Date: Thu, 11 Apr 2024 23:32:29 +0000
Subject: [PATCH 1/2] fix(ext/fs): truncate files when a ReadableStream is
 passed to writeFile

Closes #19697
---
 ext/fs/30_fs.js               |  1 +
 tests/unit/write_file_test.ts | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/ext/fs/30_fs.js b/ext/fs/30_fs.js
index b6cd2d1f136776..e99c9837a315ab 100644
--- a/ext/fs/30_fs.js
+++ b/ext/fs/30_fs.js
@@ -926,6 +926,7 @@ async function writeFile(
         append: options.append ?? false,
         create: options.create ?? true,
         createNew: options.createNew ?? false,
+        truncate: true,
         write: true,
       });
       await data.pipeTo(file.writable, {
diff --git a/tests/unit/write_file_test.ts b/tests/unit/write_file_test.ts
index 6cd08e2d14db98..29780446cf63ea 100644
--- a/tests/unit/write_file_test.ts
+++ b/tests/unit/write_file_test.ts
@@ -425,3 +425,21 @@ Deno.test(
     assertEquals(Deno.readFileSync(filename), new Uint8Array([1, 2]));
   },
 );
+
+Deno.test(
+  { permissions: { read: true, write: true } },
+  async function overwriteFileWithStream() {
+    const filename = Deno.makeTempDirSync() + "/test.txt";
+    await Deno.writeFile(filename, new Uint8Array([1, 2, 3, 4]));
+
+    const stream = new ReadableStream({
+      pull(controller) {
+        controller.enqueue(new Uint8Array([1]));
+        controller.enqueue(new Uint8Array([2]));
+        controller.close();
+      },
+    });
+    await Deno.writeFile(filename, stream);
+    assertEquals(Deno.readFileSync(filename), new Uint8Array([1, 2]));
+  },
+);

From 281776512cd1f3c9a30a78c88e646b0ce0a947b5 Mon Sep 17 00:00:00 2001
From: Charlotte Som <charlotte@som.codes>
Date: Wed, 24 Apr 2024 19:14:43 +0000
Subject: [PATCH 2/2] writeFile with ReadableStream: truncate only when not
 appending

Mirrors op_fs_write_file_async behavior
---
 ext/fs/30_fs.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ext/fs/30_fs.js b/ext/fs/30_fs.js
index e99c9837a315ab..31094fb8204516 100644
--- a/ext/fs/30_fs.js
+++ b/ext/fs/30_fs.js
@@ -926,7 +926,7 @@ async function writeFile(
         append: options.append ?? false,
         create: options.create ?? true,
         createNew: options.createNew ?? false,
-        truncate: true,
+        truncate: !(options.append ?? false),
         write: true,
       });
       await data.pipeTo(file.writable, {