fix large stdout output (#2850)

* fix large stdout output

* remove skip from #2674 for testing

* add big stdout test using spawnSync

* add bunEnv on big stdout test

src/bun.js/webcore/blob.zig

@@ -1177,6 +1177,22 @@ pub const Blob = struct {
                         return;
                     }
 
+                    if (@hasField(This, "file_store")) {
+                        const pathlike = this.file_store.pathlike;
+                        if (pathlike == .fd) {
+                            this.opened_fd = pathlike.fd;
+                            Callback(this, this.opened_fd);
+                            return;
+                        }
+                    } else {
+                        const pathlike = this.file_blob.store.?.data.file.pathlike;
+                        if (pathlike == .fd) {
+                            this.opened_fd = pathlike.fd;
+                            Callback(this, this.opened_fd);
+                            return;
+                        }
+                    }
+
                     if (comptime Environment.isMac) {
                         Callback(this, this.getFdMac());
                     } else {

test/js/bun/io/big-stdout.js

@@ -0,0 +1,2 @@
+const str = "a".repeat(300000);
+await Bun.write(Bun.stdout, str);

test/js/bun/io/bun-write.test.js

@@ -1,7 +1,7 @@
 import fs from "fs";
 import { it, expect, describe } from "bun:test";
 import path from "path";
-import { gcTick, withoutAggressiveGC } from "harness";
+import { gcTick, withoutAggressiveGC, bunExe, bunEnv } from "harness";
 import { tmpdir } from "os";
 
 it("Bun.write blob", async () => {
@@ -290,3 +290,20 @@ it.skip("Bun.write('output.html', HTMLRewriter.transform(Bun.file)))", async don
   expect(await Bun.file(outpath).text()).toBe("<div><blink>it worked!</blink></div>");
   done();
 });
+
+it("#2674", async () => {
+  const file = path.join(import.meta.dir, "big-stdout.js");
+
+  const { stderr, stdout, exitCode } = Bun.spawnSync({
+    cmd: [bunExe(), "run", file],
+    env: bunEnv,
+    stderr: "pipe",
+    stdout: "pipe",
+  });
+  console.log(stderr?.toString());
+  const text = stdout?.toString();
+  expect(text?.length).toBe(300000);
+  const error = stderr?.toString();
+  expect(error?.length).toBeFalsy();
+  expect(exitCode).toBe(0);
+});