fix decoding invalid UTF-8 input (#3563)

* fix decoding invalid UTF-8 input
Close: https://github.com/oven-sh/bun/issues/3562

* add unittest

1 files changed, 9 insertions, 0 deletions

diff --git a/test/js/node/string_decoder/string-decoder.test.js b/test/js/node/string_decoder/string-decoder.test.js
index f37326678..aba73401a 100644
--- a/test/js/node/string_decoder/string-decoder.test.js
+++ b/test/js/node/string_decoder/string-decoder.test.js
@@ -241,3 +241,12 @@ for (const StringDecoder of [FakeStringDecoderCall, RealStringDecoder]) {
     });
   });
 }
+
+it("invalid utf-8 input, pr #3562", () => {
+  const decoder = new RealStringDecoder("utf-8");
+  let output = "";
+  output += decoder.write(Buffer.from("B9", "hex"));
+  output += decoder.write(Buffer.from("A9", "hex"));
+  output += decoder.end();
+  expect(output).toStrictEqual("\uFFFD\uFFFD");
+});