bake: exit a successful bun build --app through the build VM

src/runtime/bake/production.rs

@@ -112,11 +112,11 @@ pub fn build_command(ctx: Context) -> crate::Result<()> {
     // SAFETY: `init_bake` returns a freshly-allocated VM owned by this thread;
     // unique access for the rest of this function.
     let vm = unsafe { &mut *vm_ptr };
-    // defer vm.deinit() — handled by `vm.destroy()` on the unwind path below.
+    // Only the `Err` return below reaches this; the other exits are process exits.
     // Note: pass `vm_ptr` by value into the guard so the drop closure does
     // not borrow the local (`defer!` would capture `&vm_ptr`, which under
     // edition-2024 disjoint-capture rules collides with the `&mut *vm_ptr`
-    // re-borrows on the JSError path).
+    // re-borrows below).
     let _vm_guard = scopeguard::guard(vm_ptr, |p| {
         // SAFETY: p is the unique live VM on this thread; its loop is alive, so
         // queued work is released here rather than by a thread teardown.
@@ -211,28 +211,25 @@ pub fn build_command(ctx: Context) -> crate::Result<()> {
     // LIFO order — under the API lock, before the VM is destroyed.
     let mut pt = PerThread::placeholder(vm_ptr);
 
-    match build_with_vm(ctx, &cwd, &mut pt) {
+    let result = build_with_vm(ctx, &cwd, &mut pt);
+    // SAFETY: `build_with_vm` has returned, so its reborrows through `pt.vm` are
+    // dead; the VM is live until `global_exit` (or `_vm_guard`) destroys it.
+    let vm = unsafe { &mut *vm_ptr };
+    match result {
         Ok(()) => {}
         Err(crate::Error::JSError) => {
-            // SAFETY: vm.global is live for VM lifetime.
-            let global = unsafe { &*(*vm_ptr).global };
-            let err_value = global.take_exception(jsc::JsError::Thrown);
-            // SAFETY: see above.
-            unsafe {
-                (*vm_ptr)
-                    .print_error_like_object_to_console(err_value.to_error().unwrap_or(err_value))
-            };
-            // SAFETY: see above.
-            let vm = unsafe { &mut *vm_ptr };
+            let err_value = vm.global().take_exception(jsc::JsError::Thrown);
+            vm.print_error_like_object_to_console(err_value.to_error().unwrap_or(err_value));
             if vm.exit_handler.exit_code == 0 {
                 vm.exit_handler.exit_code = 1;
             }
-            vm.on_exit();
-            vm.global_exit();
         }
         Err(e) => return Err(e),
     }
-    Ok(())
+
+    // Success must exit through the VM too: 'exit' handlers, process.exitCode, VM teardown.
+    vm.on_exit();
+    vm.global_exit()
 }
 
 /// Ported inline from `bun.bun_js.failWithBuildError` to avoid the

test/bake/dev/production.test.ts

@@ -1,8 +1,8 @@
 import { describe, expect, test } from "bun:test";
 import { existsSync } from "fs";
-import { bunEnv, bunExe } from "harness";
+import { bunEnv, bunExe, isASAN } from "harness";
 import path from "path";
-import { tempDirWithBakeDeps } from "../bake-harness";
+import { tempDirWithBakeDeps, WAIT_MULTIPLIER } from "../bake-harness";
 
 const normalizePath = (path: string) => (process.platform === "win32" ? path.replaceAll("\\", "/") : path);
 const platformPath = (path: string) => (process.platform === "win32" ? path.replaceAll("/", "\\") : path);
@@ -594,4 +594,124 @@ export default function IndexPage() {
     // Verify NO JavaScript imports are included in the HTML
     expect(htmlContent).not.toContain('<script type="module"');
   });
+
+  // A build that succeeds has to leave through the build VM's exit sequence
+  // (`on_exit` + `global_exit`), like a build that throws already does: that is
+  // what runs the 'exit' handlers, applies process.exitCode and, under
+  // BUN_DESTRUCT_VM_ON_EXIT, destroys the JSC heap. Before, it returned and
+  // exited the process directly, skipping all three.
+  describe.concurrent("exits through the build VM", () => {
+    // With BUN_DESTRUCT_VM_ON_EXIT set, global_exit tears the VM down before the
+    // process exits, so the exit codes asserted below also show that a build
+    // VM's teardown completes on every platform, not only on the ASAN lane that
+    // looks at what it frees.
+    const env = { ...bunEnv, BUN_DESTRUCT_VM_ON_EXIT: "1" };
+
+    const onExitConfig = `
+      process.on("exit", code => console.log("exit event: " + code));
+      export default { app: { framework: "react" } };
+    `;
+
+    // Each case is a full react build on a debug (and ASAN) binary, and the
+    // LSan case also symbolizes its report, which the default timeout does not
+    // cover; WAIT_MULTIPLIER is how the bake harness budgets production builds.
+    const timeout = 30_000 * WAIT_MULTIPLIER;
+
+    test(
+      "a rendered build runs 'exit' handlers and exits with process.exitCode",
+      async () => {
+        const dir = await tempDirWithBakeDeps("bake-production-exit-rendered", {
+          "app.ts": onExitConfig,
+          "pages/index.tsx": `
+            process.exitCode = 3;
+            export default function IndexPage() {
+              return <div>Hello World</div>;
+            }
+          `,
+        });
+
+        const { stdout, exitCode } = await Bun.$`${bunExe()} build --app ./app.ts`
+          .cwd(dir)
+          .env(env)
+          .quiet()
+          .throws(false);
+
+        expect(await Bun.file(path.join(dir, "dist", "index.html")).text()).toContain("Hello World");
+        expect(stdout.toString()).toBe("done\nexit event: 3\n");
+        expect(exitCode).toBe(3);
+      },
+      timeout,
+    );
+
+    test(
+      "a build with nothing to render runs 'exit' handlers",
+      async () => {
+        const dir = await tempDirWithBakeDeps("bake-production-exit-no-routes", {
+          "app.ts": onExitConfig,
+        });
+
+        const { stdout, exitCode } = await Bun.$`${bunExe()} build --app ./app.ts`
+          .cwd(dir)
+          .env(env)
+          .quiet()
+          .throws(false);
+
+        expect(stdout.toString()).toBe("done\nexit event: 0\n");
+        expect(exitCode).toBe(0);
+      },
+      timeout,
+    );
+
+    // The natives behind these objects are released by their wrappers'
+    // finalizers, so a build that exits without destroying its VM leaves all of
+    // them for LeakSanitizer to report. The page creates them while it renders:
+    // bun-framework-react's own prerender creates the first three kinds the same
+    // way (that is how the bug was found), and leaksan.supp would hide the same
+    // objects if they were created while the module is evaluated. The report
+    // cannot be required to be empty yet because the build's transpilers still
+    // leak (#38233), which is also what keeps this file in
+    // test/no-validate-leaksan.txt.
+    test.skipIf(!isASAN)(
+      "a rendered build frees the natives its JS objects own",
+      async () => {
+        const dir = await tempDirWithBakeDeps("bake-production-exit-teardown", {
+          "app.ts": `export default { app: { framework: "react" } };`,
+          "pages/index.tsx": `
+            export default function IndexPage() {
+              globalThis.keepUntilExit = [
+                new TextDecoder(),
+                new Blob(["prerender"]),
+                setImmediate(() => {}),
+                new Bun.CryptoHasher("sha256"),
+              ];
+              return <div>Hello World</div>;
+            }
+          `,
+        });
+
+        const { stdout, stderr } = await Bun.$`${bunExe()} build --app ./app.ts`
+          .cwd(dir)
+          .env({
+            ...env,
+            ASAN_OPTIONS: [bunEnv.ASAN_OPTIONS, "detect_leaks=1"].filter(Boolean).join(":"),
+            LSAN_OPTIONS: [
+              bunEnv.LSAN_OPTIONS,
+              `print_suppressions=0:suppressions=${path.join(import.meta.dirname, "../../leaksan.supp")}`,
+            ]
+              .filter(Boolean)
+              .join(":"),
+          })
+          .quiet()
+          .throws(false);
+
+        expect(await Bun.file(path.join(dir, "dist", "index.html")).text()).toContain("Hello World");
+        expect(stdout.toString()).toBe("done\n");
+        const leaked = ["TextDecoder", "Blob", "ImmediateObject", "CryptoHasher"].filter(type =>
+          stderr.toString().includes(type),
+        );
+        expect(leaked).toEqual([]);
+      },
+      timeout,
+    );
+  });
 });

test/no-validate-leaksan.txt

@@ -337,7 +337,10 @@ test/napi/node-napi-tests/test/js-native-api/6_object_wrap/do.test.ts
 # LSAN per-spawn adds no coverage and slows the file significantly.
 test/napi/uv_stub.test.ts
 
+# `bun build --app` still leaks its transpilers (#38233) and, with "use client"
+# components, a ServerComponentParseTask (#38004); remove once both have landed.
 test/bake/dev/production.test.ts
+
 test/js/third_party/pg-gateway/pglite.test.ts
 test/js/bun/test/parallel/test-integration-rspack.ts