fix-subprocess-argument-missing (#6407)

* fix-subprocess-argument-missing

* fix-tests

* nitpick, these should === not just be undefined

---------

Co-authored-by: dave caruso <me@paperdave.net>

4 files changed, 40 insertions, 2 deletions

diff --git a/src/bun.js/api/bun/subprocess.zig b/src/bun.js/api/bun/subprocess.zig
index b6e27d287..1bed014f4 100644
--- a/src/bun.js/api/bun/subprocess.zig
+++ b/src/bun.js/api/bun/subprocess.zig
@@ -2060,7 +2060,7 @@ pub const Subprocess = struct {
                     const result = cb.callWithThis(
                         this.globalThis,
                         this.this_jsvalue,
-                        &[_]JSValue{data},
+                        &[_]JSValue{ data, this.this_jsvalue },
                     );
                     data.ensureStillAlive();
                     if (result.isAnyError()) {
diff --git a/test/js/bun/spawn/bun-ipc-child-respond.js b/test/js/bun/spawn/bun-ipc-child-respond.js
new file mode 100644
index 000000000..5cf3ce97f
--- /dev/null
+++ b/test/js/bun/spawn/bun-ipc-child-respond.js
@@ -0,0 +1,4 @@
+
+process.on("message", (message) => {
+    process.send("pong:" + message);
+});
\ No newline at end of file
diff --git a/test/js/bun/spawn/bun-ipc-child.js b/test/js/bun/spawn/bun-ipc-child.js
new file mode 100644
index 000000000..5bad9f49a
--- /dev/null
+++ b/test/js/bun/spawn/bun-ipc-child.js
@@ -0,0 +1 @@
+process.send("hello");
\ No newline at end of file
diff --git a/test/js/bun/spawn/spawn.test.ts b/test/js/bun/spawn/spawn.test.ts
index 897a16635..139eddb33 100644
--- a/test/js/bun/spawn/spawn.test.ts
+++ b/test/js/bun/spawn/spawn.test.ts
@@ -1,7 +1,8 @@
 import { ArrayBufferSink, readableStreamToText, spawn, spawnSync, write } from "bun";
 import { describe, expect, it } from "bun:test";
-import { gcTick as _gcTick, bunEnv } from "harness";
+import { gcTick as _gcTick, bunExe } from "harness";
 import { rmSync, writeFileSync } from "node:fs";
+import path from "path";
 
 for (let [gcTick, label] of [
   [_gcTick, "gcTick"],
@@ -440,6 +441,38 @@ for (let [gcTick, label] of [
           });
         }
       });
+
+      describe("ipc", () => {
+        it("the subprocess should be defined and the child should send", done => {
+          gcTick();
+          const returned_subprocess = spawn([bunExe(), path.join(__dirname, "bun-ipc-child.js")], {
+            ipc: (message, subProcess) => {
+              expect(subProcess).toBe(returned_subprocess);
+              expect(message).toBe("hello");
+              subProcess.kill();
+              done();
+              gcTick();
+            },
+          });
+        });
+
+        it("the subprocess should receive the parent message and respond back", done => {
+          gcTick();
+
+          const parentMessage = "I am your father";
+          const childProc = spawn([bunExe(), path.join(__dirname, "bun-ipc-child-respond.js")], {
+            ipc: (message, subProcess) => {
+              expect(message).toBe(`pong:${parentMessage}`);
+              subProcess.kill();
+              done();
+              gcTick();
+            },
+          });
+
+          childProc.send(parentMessage);
+          gcTick();
+        });
+      });
     });
   });
 }