Pass a Buffer to a patched stdio write from an encoded data listener

A byte write to a replaced process.stdout.write or process.stderr.write
was boxed with the 'data' chunk helper, which answers a string while a
listener of a socket or HTTP response with setEncoding("utf8") runs. A
`process.stdout.write(buffer)` from such a listener reached the
replacement as a string. Node passes the Buffer it was given.

The stdio hook now boxes a byte write as a Buffer whatever listener is
running.

packages/compiler/test/ts7/baselines/order-parity/tests/corpus/stdout-patch-buffer-from-encoded-data/main.ts.json

@@ -0,0 +1,7 @@
+{
+ "order": [
+  "<repo>/tests/corpus/stdout-patch-buffer-from-encoded-data/patch.mjs",
+  "<repo>/tests/corpus/stdout-patch-buffer-from-encoded-data/main.ts"
+ ],
+ "diags": []
+}

packages/runtime/src/scr_events.c

@@ -1534,9 +1534,12 @@ static bool scr_stdio_intercept(int fd, const void *data, size_t length, int fla
   }
   ScrDyn *chunk;
   if (flags & SCR_STDIO_HOOK_BYTES) {
+    /* Always a Buffer: a write from a 'data' listener of a stream with an
+     * encoding set is still the bytes it was given. */
     ScrBytes *b = scr_bytes_new(SCR_BYTES_U8, (double)length);
     memcpy(b->data, data, length);
-    chunk = scr_dyn_new_chunk(b);
+    b->is_buffer = true;
+    chunk = scr_dyn_new_bytes(b);
     scr_bytes_release(b);
   } else {
     ScrStr *text = scr_str_new(data, length);

tests/corpus/stdout-patch-buffer-from-encoded-data/main.ts

@@ -0,0 +1,32 @@
+// A Buffer written to a replaced process.stdout.write from a 'data' listener
+// of a socket or an HTTP response with setEncoding("utf8") arrives as a
+// Buffer; the listener's own chunks are strings. patch.mjs installs the
+// replacement and prints what it received at exit.
+import * as http from "node:http";
+import * as net from "node:net";
+import "./patch.mjs";
+
+const tcp = net.createServer((socket) => socket.end("tcp-data"));
+tcp.listen(0, "127.0.0.1", () => {
+  const port = (tcp.address() as net.AddressInfo).port;
+  const client = net.connect(port, "127.0.0.1");
+  client.setEncoding("utf8");
+  client.on("data", (text: string) => {
+    process.stdout.write(Buffer.from(`socket ${typeof text} ${text}`));
+    process.stdout.write(`socket text ${text}`);
+  });
+  client.on("end", () => {
+    tcp.close();
+    const server = http.createServer((req, res) => res.end("http-data"));
+    server.listen(0, "127.0.0.1", () => {
+      const httpPort = (server.address() as net.AddressInfo).port;
+      http.get(`http://127.0.0.1:${httpPort}/`, (res) => {
+        res.setEncoding("utf8");
+        res.on("data", (text: string) => {
+          process.stdout.write(Buffer.from(`response ${typeof text} ${text}`));
+        });
+        res.on("end", () => server.close());
+      });
+    });
+  });
+});

tests/corpus/stdout-patch-buffer-from-encoded-data/patch.mjs

@@ -0,0 +1,8 @@
+// Replaces process.stdout.write with a recorder; an exit handler prints what it saw.
+const seen = [];
+process.stdout.write = function (chunk) {
+  const kind = typeof chunk === "string" ? "string" : Buffer.isBuffer(chunk) ? "Buffer" : typeof chunk;
+  seen.push(`${kind}:${String(chunk)}`);
+  return true;
+};
+process.on("exit", () => process.stderr.write(`${seen.join("\n")}\n`));

tests/harness/corpus-costs/stdout-patch-buffer-from-encoded-data/main.ts.json

@@ -0,0 +1 @@
+{ "plain": 5044, "san": 13845 }