From 68193ee1917b442914ef6830c6eae5404eb85bf2 Mon Sep 17 00:00:00 2001
From: Marco Ippolito <marcoippolito54@gmail.com>
Date: Mon, 23 Jan 2023 22:13:03 +0100
Subject: [PATCH 1/4] stream: validate writable defaultEncoding

---
 lib/internal/streams/writable.js              |  8 ++++++-
 .../test-stream-writable-decoded-encoding.js  | 24 +++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/lib/internal/streams/writable.js b/lib/internal/streams/writable.js
index c4d95df9ac7153..4c1452120d4fc9 100644
--- a/lib/internal/streams/writable.js
+++ b/lib/internal/streams/writable.js
@@ -122,7 +122,13 @@ function WritableState(options, stream, isDuplex) {
   // Crypto is kind of old and crusty.  Historically, its default string
   // encoding is 'binary' so we have to make this configurable.
   // Everything else in the universe uses 'utf8', though.
-  this.defaultEncoding = (options && options.defaultEncoding) || 'utf8';
+  const defaultEncoding = options?.defaultEncoding;
+
+  if (defaultEncoding && !Buffer.isEncoding(defaultEncoding)) {
+    throw new ERR_UNKNOWN_ENCODING(defaultEncoding);
+  }
+
+  this.defaultEncoding = defaultEncoding || 'utf8';
 
   // Not an actual buffer we keep track of, but a measurement
   // of how much we're waiting to get pushed to some underlying
diff --git a/test/parallel/test-stream-writable-decoded-encoding.js b/test/parallel/test-stream-writable-decoded-encoding.js
index 578208a84bdec0..b2caef11d01d9f 100644
--- a/test/parallel/test-stream-writable-decoded-encoding.js
+++ b/test/parallel/test-stream-writable-decoded-encoding.js
@@ -56,3 +56,27 @@ class MyWritable extends stream.Writable {
   m.write('some-text', 'utf8');
   m.end();
 }
+
+{
+  assert.throws(() => {
+    const m = new MyWritable(null, {
+      defaultEncoding: 'my invalid encoding',
+    });
+    m.end();
+  }, {
+    code: 'ERR_UNKNOWN_ENCODING',
+  });
+}
+
+{
+  const w = new MyWritable(function(isBuffer, type, enc) {
+    assert(!isBuffer);
+    assert.strictEqual(type, 'string');
+    assert.strictEqual(enc, 'hex');
+  }, {
+    defaultEncoding: 'hex',
+    decodeStrings: false
+  });
+  w.write('asd');
+  w.end();
+}

From f9a2d212e29ff4c94f6279a5f0ab5312bc3039f5 Mon Sep 17 00:00:00 2001
From: Marco Ippolito <marcoippolito54@gmail.com>
Date: Tue, 24 Jan 2023 09:32:37 +0100
Subject: [PATCH 2/4] stream: test falsy defaultEncoding

---
 .../test-stream-writable-decoded-encoding.js        | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/test/parallel/test-stream-writable-decoded-encoding.js b/test/parallel/test-stream-writable-decoded-encoding.js
index b2caef11d01d9f..90fea7059a8ea4 100644
--- a/test/parallel/test-stream-writable-decoded-encoding.js
+++ b/test/parallel/test-stream-writable-decoded-encoding.js
@@ -80,3 +80,16 @@ class MyWritable extends stream.Writable {
   w.write('asd');
   w.end();
 }
+
+{
+  const w = new MyWritable(function(isBuffer, type, enc) {
+    assert(!isBuffer);
+    assert.strictEqual(type, 'string');
+    assert.strictEqual(enc, 'utf8');
+  }, {
+    defaultEncoding: null,
+    decodeStrings: false
+  });
+  w.write('asd');
+  w.end();
+}

From 1b962519f3c9658809638f4f4f80307ad30b72eb Mon Sep 17 00:00:00 2001
From: Marco Ippolito <marcoippolito54@gmail.com>
Date: Tue, 24 Jan 2023 10:07:00 +0100
Subject: [PATCH 3/4] stream: test object mode

---
 test/parallel/test-stream-writable-decoded-encoding.js | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/test/parallel/test-stream-writable-decoded-encoding.js b/test/parallel/test-stream-writable-decoded-encoding.js
index 90fea7059a8ea4..e3caa9928fda8c 100644
--- a/test/parallel/test-stream-writable-decoded-encoding.js
+++ b/test/parallel/test-stream-writable-decoded-encoding.js
@@ -93,3 +93,13 @@ class MyWritable extends stream.Writable {
   w.write('asd');
   w.end();
 }
+
+{
+  const m = new MyWritable(function(isBuffer, type, enc) {
+    assert.strictEqual(type, 'object');
+    assert.strictEqual(enc, 'utf8');
+  }, { defaultEncoding: 'hex',
+       objectMode: true });
+  m.write({ foo: 'bar' }, 'utf8');
+  m.end();
+}

From 958633dd2ad99e170a38fec0df09264c9f94328c Mon Sep 17 00:00:00 2001
From: Marco Ippolito <marcoippolito54@gmail.com>
Date: Wed, 25 Jan 2023 10:27:25 +0100
Subject: [PATCH 4/4] stream: refactor code style

---
 lib/internal/streams/writable.js | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/internal/streams/writable.js b/lib/internal/streams/writable.js
index 4c1452120d4fc9..5d01c854fbd16d 100644
--- a/lib/internal/streams/writable.js
+++ b/lib/internal/streams/writable.js
@@ -123,13 +123,14 @@ function WritableState(options, stream, isDuplex) {
   // encoding is 'binary' so we have to make this configurable.
   // Everything else in the universe uses 'utf8', though.
   const defaultEncoding = options?.defaultEncoding;
-
-  if (defaultEncoding && !Buffer.isEncoding(defaultEncoding)) {
+  if (defaultEncoding == null) {
+    this.defaultEncoding = 'utf8';
+  } else if (Buffer.isEncoding(defaultEncoding)) {
+    this.defaultEncoding = defaultEncoding;
+  } else {
     throw new ERR_UNKNOWN_ENCODING(defaultEncoding);
   }
 
-  this.defaultEncoding = defaultEncoding || 'utf8';
-
   // Not an actual buffer we keep track of, but a measurement
   // of how much we're waiting to get pushed to some underlying
   // socket or file.