[breaking] `onExit` callback in Bun.spawn sets the first property to be the Subprocess object

Sometimes Bun.spawn calls the onExit callback before the Bun.spawn() callback is called.

Instead of delaying a tick, we set the `Subprocess` to be the first argument to the `onExit` callback now.

2 files changed, 40 insertions, 5 deletions

diff --git a/packages/bun-types/bun.d.ts b/packages/bun-types/bun.d.ts
index ccdcf2c2c..c9ea2fb66 100644
--- a/packages/bun-types/bun.d.ts
+++ b/packages/bun-types/bun.d.ts
@@ -1,3 +1,5 @@
+import { SignalConstants } from "os";
+
 interface VoidFunction {
   (): void;
 }
@@ -2617,13 +2619,21 @@ declare module "bun" {
        * ```ts
        * const subprocess = spawn({
        *  cmd: ["echo", "hello"],
-       *  onExit: (code) => {
+       *  onExit: (subprocess, code) => {
        *    console.log(`Process exited with code ${code}`);
        *   },
        * });
        * ```
        */
-      onExit?: (exitCode: number) => void | Promise<void>;
+      onExit?(
+        subprocess: Subprocess,
+        exitCode: number | null,
+        signalCode: number | null,
+        /**
+         * If an error occured in the call to waitpid2, this will be the error.
+         */
+        error?: Errorlike,
+      ): void | Promise<void>;
     }
   }
 
@@ -2661,6 +2671,25 @@ declare module "bun" {
     readonly exited: Promise<number>;
 
     /**
+     * Synchronously get the exit code of the process
+     *
+     * If the process hasn't exited yet, this will return `null`
+     */
+    readonly exitCode: number | null;
+
+    /**
+     * Synchronously get the signal code of the process
+     *
+     * If the process never sent a signal code, this will return `null`
+     *
+     * To receive signal code changes, use the `onExit` callback.
+     *
+     * If the signal code is unknown, it will return the original signal code
+     * number, but that case should essentially never happen.
+     */
+    readonly signalCode: Signals | null;
+
+    /**
      * Has the process exited?
      */
     readonly killed: boolean;
diff --git a/src/bun.js/api/bun/subprocess.zig b/src/bun.js/api/bun/subprocess.zig
index fe09746eb..53f0da03e 100644
--- a/src/bun.js/api/bun/subprocess.zig
+++ b/src/bun.js/api/bun/subprocess.zig
@@ -1571,14 +1571,20 @@ pub const Subprocess = struct {
             else
                 JSC.JSValue.jsUndefined();
 
+            const this_value = if (this_jsvalue.isEmptyOrUndefinedOrNull()) JSC.JSValue.jsUndefined() else this_jsvalue;
+            this_value.ensureStillAlive();
+
             const args = [_]JSValue{
-                exit_value,
+                this_value,
+                this.getExitCode(globalThis),
+                this.getSignalCode(globalThis),
                 waitpid_value,
             };
 
-            const result = callback.call(
+            const result = callback.callWithThis(
                 globalThis,
-                args[0 .. @as(usize, @boolToInt(this.exit_code != null)) + @as(usize, @boolToInt(this.waitpid_err != null))],
+                this_value,
+                &args,
             );
 
             if (result.isAnyError(globalThis)) {