fix(child_process) unref next tick so exit/close event can be fired before application exits (#5481)

* unref next tick so exit callback can be called

* fmt + test

* oops

* add ref_count

* update pending

* comment and fix

2 files changed, 35 insertions, 0 deletions

diff --git a/test/js/node/child_process/child_process.test.ts b/test/js/node/child_process/child_process.test.ts
index baf422bc9..8c24ef55e 100644
--- a/test/js/node/child_process/child_process.test.ts
+++ b/test/js/node/child_process/child_process.test.ts
@@ -2,6 +2,8 @@ import { describe, it, expect } from "bun:test";
 import { ChildProcess, spawn, execFile, exec, fork, spawnSync, execFileSync, execSync } from "node:child_process";
 import { tmpdir } from "node:os";
 import { promisify } from "node:util";
+import { bunExe, bunEnv } from "harness";
+import path from "path";
 
 const debug = process.env.DEBUG ? console.log : () => {};
 
@@ -308,3 +310,23 @@ describe("Bun.spawn()", () => {
   //   expect(child.pid).toBe(undefined);
   // });
 });
+
+it("should call close and exit before process exits", async () => {
+  const proc = Bun.spawn({
+    cmd: [bunExe(), path.join("fixtures", "child-process-exit-event.js")],
+    cwd: import.meta.dir,
+    env: bunEnv,
+    stdout: "pipe",
+  });
+  await proc.exited;
+  expect(proc.exitCode).toBe(0);
+  let data = "";
+  const reader = proc.stdout.getReader();
+  while (true) {
+    const { done, value } = await reader.read();
+    if (done) break;
+    data += new TextDecoder().decode(value);
+  }
+  expect(data).toContain("closeHandler called");
+  expect(data).toContain("exithHandler called");
+});
diff --git a/test/js/node/child_process/fixtures/child-process-exit-event.js b/test/js/node/child_process/fixtures/child-process-exit-event.js
new file mode 100644
index 000000000..4400ace1b
--- /dev/null
+++ b/test/js/node/child_process/fixtures/child-process-exit-event.js
@@ -0,0 +1,13 @@
+const { spawn } = require("node:child_process");
+
+function exitHandler() {
+  console.log("exithHandler called");
+}
+function closeHandler() {
+  console.log("closeHandler called");
+}
+
+const p = spawn("bun", ["--version"]);
+
+p.on("exit", exitHandler);
+p.on("close", closeHandler);