From 3a7abe6906c54f9c628215c2b71d67e8db25a519 Mon Sep 17 00:00:00 2001
From: Florian Schwalm <68847951+egfx-notifications@users.noreply.github.com>
Date: Sun, 12 Nov 2023 20:47:03 +0100
Subject: [PATCH] fix(ext/web): Prevent TextDecoderStream resource leak on
 stream cancellation (#21074)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This PR uses the new `cancel` method of `TransformStream` to properly
clean up the internal `TextDecoder` used in `TextDecoderStream` if the
stream is cancelled.

Fixes #13142

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>
---
 cli/tests/unit/text_encoding_test.ts | 17 +++++++++++++++++
 ext/web/06_streams.js                |  4 ++++
 ext/web/08_text_encoding.js          |  8 ++++++++
 3 files changed, 29 insertions(+)

diff --git a/cli/tests/unit/text_encoding_test.ts b/cli/tests/unit/text_encoding_test.ts
index b76e9a9bf0fa19..270fd07a835e69 100644
--- a/cli/tests/unit/text_encoding_test.ts
+++ b/cli/tests/unit/text_encoding_test.ts
@@ -319,3 +319,20 @@ Deno.test(function binaryEncode() {
     assertEquals(Array.from(bytes), decodeBinary(binaryString));
   }
 });
+
+Deno.test(
+  { permissions: { read: true } },
+  async function textDecoderStreamCleansUpOnCancel() {
+    const filename = "cli/tests/testdata/assets/hello.txt";
+    const file = await Deno.open(filename);
+    const readable = file.readable.pipeThrough(new TextDecoderStream());
+    const chunks = [];
+    for await (const chunk of readable) {
+      chunks.push(chunk);
+      // breaking out of the loop prevents normal shutdown at end of async iterator values and triggers the cancel method of the stream instead
+      break;
+    }
+    assertEquals(chunks.length, 1);
+    assertEquals(chunks[0].length, 12);
+  },
+);
diff --git a/ext/web/06_streams.js b/ext/web/06_streams.js
index c5306ca9c3351f..7ce045e6839200 100644
--- a/ext/web/06_streams.js
+++ b/ext/web/06_streams.js
@@ -6680,6 +6680,10 @@ webidl.converters.Transformer = webidl
       key: "flush",
       converter: webidl.converters.Function,
     },
+    {
+      key: "cancel",
+      converter: webidl.converters.Function,
+    },
     {
       key: "readableType",
       converter: webidl.converters.any,
diff --git a/ext/web/08_text_encoding.js b/ext/web/08_text_encoding.js
index 45dbad53822ca7..5f8391e124c2f2 100644
--- a/ext/web/08_text_encoding.js
+++ b/ext/web/08_text_encoding.js
@@ -301,6 +301,14 @@ class TextDecoderStream {
           return PromiseReject(err);
         }
       },
+      cancel: (_reason) => {
+        try {
+          const _ = this.#decoder.decode();
+          return PromiseResolve();
+        } catch (err) {
+          return PromiseReject(err);
+        }
+      },
     });
     this[webidl.brand] = webidl.brand;
   }