fix(ext/node): don't encode buffer data as utf8 in http2 (#24016)

ext/node/polyfills/http2.ts

@@ -933,25 +933,23 @@ export class ClientHttp2Stream extends Duplex {
 
   // TODO(bartlomieju): clean up
   _write(chunk, encoding, callback?: () => void) {
-    debugHttp2(">>> _write", callback);
+    debugHttp2(">>> _write", encoding, callback);
     if (typeof encoding === "function") {
       callback = encoding;
-      encoding = "utf8";
+      encoding = this.#encoding;
     }
     let data;
-    if (typeof encoding === "string") {
+    if (encoding === "utf8") {
       data = ENCODER.encode(chunk);
-    } else {
+    } else if (encoding === "buffer") {
+      this.#encoding = encoding;
       data = chunk.buffer;
     }
 
     this.#requestPromise
       .then(() => {
         debugHttp2(">>> _write", this.#rid, data, encoding, callback);
-        return op_http2_client_send_data(
-          this.#rid,
-          data,
-        );
+        return op_http2_client_send_data(this.#rid, new Uint8Array(data));
       })
       .then(() => {
         callback?.();

tests/unit_node/http2_test.ts

@@ -1,6 +1,9 @@
 // Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
 
 import * as http2 from "node:http2";
+import { Buffer } from "node:buffer";
+import { readFile } from "node:fs/promises";
+import { join } from "node:path";
 import * as net from "node:net";
 import { assert, assertEquals } from "@std/assert/mod.ts";
 import { curlRequest } from "../unit/test_util.ts";
@@ -164,3 +167,39 @@ Deno.test("[node/http2.createServer()]", {
   // Issue: https://github.com/denoland/deno/issues/22764
   await new Promise<void>((resolve) => server.on("close", resolve));
 });
+
+Deno.test("[node/http2 client] write image buffer on request stream works", async () => {
+  const url = "https://localhost:5545";
+  const client = http2.connect(url);
+  client.on("error", (err) => console.error(err));
+
+  const imagePath = join(import.meta.dirname!, "testdata", "green.jpg");
+  const buffer = await readFile(imagePath);
+  const req = client.request({ ":method": "POST", ":path": "/echo_server" });
+  req.write(buffer, (err) => {
+    if (err) throw err;
+  });
+
+  let receivedData: Buffer;
+  req.on("data", (chunk) => {
+    if (!receivedData) {
+      receivedData = chunk;
+    } else {
+      receivedData = Buffer.concat([receivedData, chunk]);
+    }
+  });
+  req.end();
+
+  const endPromise = Promise.withResolvers<void>();
+  setTimeout(() => {
+    try {
+      client.close();
+    } catch (_) {
+      // pass
+    }
+    endPromise.resolve();
+  }, 2000);
+
+  await endPromise.promise;
+  assertEquals(receivedData!, buffer);
+});