fix text decode trim (#4495)

* remove trim

* separate function

* a test

* trim when `stream` is true

---------

Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/test/js/web/encoding/text-decoder.test.js b/test/js/web/encoding/text-decoder.test.js
index 8ec097f31..4991cf361 100644
--- a/test/js/web/encoding/text-decoder.test.js
+++ b/test/js/web/encoding/text-decoder.test.js
@@ -233,6 +233,20 @@ describe("TextDecoder", () => {
     }).toThrow(TypeError);
   });
 
+  it("should not trim invalid byte sequences when fatal is false", () => {
+    const buf = Buffer.from([77, 97, 110, 32, 208, 129, 240, 164, 173]);
+    const received = new TextDecoder("utf-8").decode(buf);
+    const expected = "Man Ё\ufffd";
+    expect(received).toBe(expected);
+  });
+
+  it("should trim when stream is true", () => {
+    const buf = Buffer.from([77, 97, 110, 32, 208, 129, 240, 164, 173]);
+    const received = new TextDecoder("utf-8").decode(buf, { stream: true });
+    const expected = "Man Ё";
+    expect(received).toBe(expected);
+  });
+
   it("constructor should set values", () => {
     const decoder = new TextDecoder("utf-8", { fatal: true, ignoreBOM: false });
     expect(decoder.fatal).toBe(true);