Merge branch 'main' into claude/fix-spawn-pipe-cleanup-on-error

### Problem

The bundler's `__toESM` helper creates a new getter-wrapped proxy object
every time a CJS
module is imported. In a large app, a popular dependency like React can
be imported 600+
times — each creating a fresh object with ~44 getter properties. This
produces ~27K
unnecessary `GetterSetter` objects, ~25K closures, and ~25K
`JSLexicalEnvironment` scope
objects at startup.

Additionally, `__export` and `__exportValue` use `var`-scoped loop
variables captured by
setter closures, meaning all setters incorrectly reference the last
iterated key (a latent
  bug).

### Changes

1. **`__toESM`: add WeakMap cache** — deduplicate repeated wrappings of
the same CJS
module. Two caches (one per `isNodeMode` value) to handle both import
modes correctly.
2. **Replace closures with `.bind()`** — `() => obj[key]` becomes
`__accessProp.bind(obj,
key)`. BoundFunction is cheaper than Function + JSLexicalEnvironment,
and frees the for-in
  `JSPropertyNameEnumerator` from the closure scope.
3. **Fix var-scoping bug in `__export`/`__exportValue`** — setter
closures captured a
shared `var name` and would all modify the last iterated key. `.bind()`
eagerly captures
the correct key per iteration.
4. **`__toCommonJS`: `.map()` → `for..of`** — eliminates throwaway array
allocation.
5. **`__reExport`: single `getOwnPropertyNames` call** — was calling it
twice when
`secondTarget` was provided.

### Impact (measured on a ~23MB single-bundle app with 600+ React
imports)

| Metric | Before | After | Delta |
|--------|--------|-------|-------|
| **Total objects** | 745,985 | 664,001 | **-81,984 (-11%)** |
| **Heap size** | 115 MB | 111 MB | **-4 MB** |
| GetterSetter | 34,625 | 13,428 | -21,197 (-61%) |
| Function | 221,302 | 197,024 | -24,278 (-11%) |
| JSLexicalEnvironment | 70,101 | 44,633 | -25,468 (-36%) |
| Structure | 40,254 | 39,762 | -492 |

src/bun.js/api/bun/process.zig

@@ -1087,10 +1087,33 @@ pub const WindowsSpawnOptions = struct {
         dup2: struct { out: bun.jsc.Subprocess.StdioKind, to: bun.jsc.Subprocess.StdioKind },
 
         pub fn deinit(this: *const Stdio) void {
-            if (this.* == .buffer) {
-                bun.default_allocator.destroy(this.buffer);
+            switch (this.*) {
+                .buffer => |pipe| closePipeAndDestroy(pipe),
+                .ipc => |pipe| closePipeAndDestroy(pipe),
+                else => {},
             }
         }
+
+        /// Close a pipe that may have been initialized with uv_pipe_init.
+        /// If the pipe was initialized, we must call uv_close before freeing
+        /// to properly remove it from the loop's handle queue; otherwise
+        /// the handle queue linked list becomes corrupted.
+        fn closePipeAndDestroy(pipe: *bun.windows.libuv.Pipe) void {
+            if (pipe.loop == null or pipe.isClosed()) {
+                // Never initialized or already fully closed — safe to free directly.
+                bun.default_allocator.destroy(pipe);
+            } else if (!pipe.isClosing()) {
+                // Initialized and not yet closing — must uv_close to remove from handle queue.
+                pipe.close(&onPipeCloseForDeinit);
+            }
+            // else: isClosing — uv_close was already called, the pending close
+            // callback owns the lifetime. This shouldn't happen in practice since
+            // deinit is only called on the error path before any close is initiated.
+        }
+
+        fn onPipeCloseForDeinit(pipe: *bun.windows.libuv.Pipe) callconv(.c) void {
+            bun.default_allocator.destroy(pipe);
+        }
     };
 
     pub fn deinit(this: *const WindowsSpawnOptions) void {
@@ -1629,9 +1652,10 @@ pub fn spawnProcessWindows(
                 stdio.flags = uv.UV_INHERIT_FD;
                 stdio.data.fd = fd_i;
             },
-            .ipc => |my_pipe| {
-                // ipc option inside stdin, stderr or stdout are not supported
-                bun.default_allocator.destroy(my_pipe);
+            .ipc => {
+                // ipc option inside stdin, stderr or stdout are not supported.
+                // Don't destroy the pipe here — the caller's deinit() will handle it
+                // (the pipe was never uv_pipe_init'd so it can be freed directly).
                 stdio.flags = uv.UV_IGNORE;
             },
             .ignore => {

src/bun.js/api/bun/spawn/stdio.zig

@@ -235,10 +235,10 @@ pub const Stdio = union(enum) {
                         return .{ .err = .blob_used_as_out };
                     }
 
-                    break :brk .{ .buffer = bun.handleOom(bun.default_allocator.create(uv.Pipe)) };
+                    break :brk .{ .buffer = createZeroedPipe() };
                 },
-                .ipc => .{ .ipc = bun.handleOom(bun.default_allocator.create(uv.Pipe)) },
-                .capture, .pipe, .array_buffer, .readable_stream => .{ .buffer = bun.handleOom(bun.default_allocator.create(uv.Pipe)) },
+                .ipc => .{ .ipc = createZeroedPipe() },
+                .capture, .pipe, .array_buffer, .readable_stream => .{ .buffer = createZeroedPipe() },
                 .fd => |fd| .{ .pipe = fd },
                 .dup2 => .{ .dup2 = .{ .out = stdio.dup2.out, .to = stdio.dup2.to } },
                 .path => |pathlike| .{ .path = pathlike.slice() },
@@ -487,6 +487,15 @@ pub const Stdio = union(enum) {
     }
 };
 
+/// Allocate a zero-initialized uv.Pipe. Zero-init is required so that
+/// `pipe.loop` is null for pipes that were never passed to `uv_pipe_init`,
+/// which `closePipeAndDestroy` relies on to decide whether `uv_close` is needed.
+fn createZeroedPipe() *bun.windows.libuv.Pipe {
+    const pipe = bun.handleOom(bun.default_allocator.create(bun.windows.libuv.Pipe));
+    pipe.* = std.mem.zeroes(bun.windows.libuv.Pipe);
+    return pipe;
+}
+
 const std = @import("std");
 
 const bun = @import("bun");

src/runtime.js

@@ -12,24 +12,32 @@ var __getOwnPropNames = Object.getOwnPropertyNames;
 var __getOwnPropDesc = Object.getOwnPropertyDescriptor;
 var __hasOwnProp = Object.prototype.hasOwnProperty;
 
+// Shared getter/setter functions: .bind(obj, key) avoids creating a closure
+// and JSLexicalEnvironment per property. BoundFunction is much cheaper.
+// Must be regular functions (not arrows) so .bind() can set `this`.
+function __accessProp(key) {
+  return this[key];
+}
+
 // This is used to implement "export * from" statements. It copies properties
 // from the imported module to the current module's ESM export object. If the
 // current module is an entry point and the target format is CommonJS, we
 // also copy the properties to "module.exports" in addition to our module's
 // internal ESM export object.
 export var __reExport = (target, mod, secondTarget) => {
-  for (let key of __getOwnPropNames(mod))
+  var keys = __getOwnPropNames(mod);
+  for (let key of keys)
     if (!__hasOwnProp.call(target, key) && key !== "default")
       __defProp(target, key, {
-        get: () => mod[key],
+        get: __accessProp.bind(mod, key),
         enumerable: true,
       });
 
   if (secondTarget) {
-    for (let key of __getOwnPropNames(mod))
+    for (let key of keys)
       if (!__hasOwnProp.call(secondTarget, key) && key !== "default")
         __defProp(secondTarget, key, {
-          get: () => mod[key],
+          get: __accessProp.bind(mod, key),
           enumerable: true,
         });
 
@@ -37,11 +45,22 @@ export var __reExport = (target, mod, secondTarget) => {
   }
 };
 
+/*__PURE__*/
+var __toESMCache_node;
+/*__PURE__*/
+var __toESMCache_esm;
+
 // Converts the module from CommonJS to ESM. When in node mode (i.e. in an
 // ".mjs" file, package.json has "type: module", or the "__esModule" export
 // in the CommonJS file is falsy or missing), the "default" property is
 // overridden to point to the original CommonJS exports object instead.
 export var __toESM = (mod, isNodeMode, target) => {
+  var canCache = mod != null && typeof mod === "object";
+  if (canCache) {
+    var cache = isNodeMode ? (__toESMCache_node ??= new WeakMap()) : (__toESMCache_esm ??= new WeakMap());
+    var cached = cache.get(mod);
+    if (cached) return cached;
+  }
   target = mod != null ? __create(__getProtoOf(mod)) : {};
   const to =
     isNodeMode || !mod || !mod.__esModule ? __defProp(target, "default", { value: mod, enumerable: true }) : target;
@@ -53,34 +72,34 @@ export var __toESM = (mod, isNodeMode, target) => {
   for (let key of __getOwnPropNames(mod))
     if (!__hasOwnProp.call(to, key))
       __defProp(to, key, {
-        get: () => mod[key],
+        get: __accessProp.bind(mod, key),
         enumerable: true,
       });
 
+  if (canCache) cache.set(mod, to);
   return to;
 };
 
 // Converts the module from ESM to CommonJS. This clones the input module
 // object with the addition of a non-enumerable "__esModule" property set
 // to "true", which overwrites any existing export named "__esModule".
-var __moduleCache = /* @__PURE__ */ new WeakMap();
-export var __toCommonJS = /* @__PURE__ */ from => {
-  var entry = __moduleCache.get(from),
+export var __toCommonJS = from => {
+  var entry = (__moduleCache ??= new WeakMap()).get(from),
     desc;
   if (entry) return entry;
   entry = __defProp({}, "__esModule", { value: true });
   if ((from && typeof from === "object") || typeof from === "function")
-    __getOwnPropNames(from).map(
-      key =>
-        !__hasOwnProp.call(entry, key) &&
+    for (var key of __getOwnPropNames(from))
+      if (!__hasOwnProp.call(entry, key))
         __defProp(entry, key, {
-          get: () => from[key],
+          get: __accessProp.bind(from, key),
           enumerable: !(desc = __getOwnPropDesc(from, key)) || desc.enumerable,
-        }),
-    );
+        });
   __moduleCache.set(from, entry);
   return entry;
 };
+/*__PURE__*/
+var __moduleCache;
 
 // When you do know the module is CJS
 export var __commonJS = (cb, mod) => () => (mod || cb((mod = { exports: {} }).exports, mod), mod.exports);
@@ -97,6 +116,10 @@ export var __name = (target, name) => {
 
 // ESM export -> CJS export
 // except, writable incase something re-exports
+var __returnValue = v => v;
+function __exportSetter(name, newValue) {
+  this[name] = __returnValue.bind(null, newValue);
+}
 
 export var __export = /* @__PURE__ */ (target, all) => {
   for (var name in all)
@@ -104,15 +127,19 @@ export var __export = /* @__PURE__ */ (target, all) => {
       get: all[name],
       enumerable: true,
       configurable: true,
-      set: newValue => (all[name] = () => newValue),
+      set: __exportSetter.bind(all, name),
     });
 };
 
+function __exportValueSetter(name, newValue) {
+  this[name] = newValue;
+}
+
 export var __exportValue = (target, all) => {
   for (var name in all) {
     __defProp(target, name, {
-      get: () => all[name],
-      set: newValue => (all[name] = newValue),
+      get: __accessProp.bind(all, name),
+      set: __exportValueSetter.bind(all, name),
       enumerable: true,
       configurable: true,
     });

test/bundler/__snapshots__/bun-build-api.test.ts.snap

@@ -2,13 +2,17 @@
 
 exports[`Bun.build Bun.write(BuildArtifact) 1`] = `
 "var __defProp = Object.defineProperty;
+var __returnValue = (v) => v;
+function __exportSetter(name, newValue) {
+  this[name] = __returnValue.bind(null, newValue);
+}
 var __export = (target, all) => {
   for (var name in all)
     __defProp(target, name, {
       get: all[name],
       enumerable: true,
       configurable: true,
-      set: (newValue) => all[name] = () => newValue
+      set: __exportSetter.bind(all, name)
     });
 };
 
@@ -31,13 +35,17 @@ NS.then(({ fn: fn2 }) => {
 
 exports[`Bun.build outdir + reading out blobs works 1`] = `
 "var __defProp = Object.defineProperty;
+var __returnValue = (v) => v;
+function __exportSetter(name, newValue) {
+  this[name] = __returnValue.bind(null, newValue);
+}
 var __export = (target, all) => {
   for (var name in all)
     __defProp(target, name, {
       get: all[name],
       enumerable: true,
       configurable: true,
-      set: (newValue) => all[name] = () => newValue
+      set: __exportSetter.bind(all, name)
     });
 };
 
@@ -58,23 +66,27 @@ NS.then(({ fn: fn2 }) => {
 "
 `;
 
-exports[`Bun.build BuildArtifact properties: hash 1`] = `"d1c7nm6t"`;
+exports[`Bun.build BuildArtifact properties: hash 1`] = `"est79qzq"`;
 
-exports[`Bun.build BuildArtifact properties + entry.naming: hash 1`] = `"rm7e36cf"`;
+exports[`Bun.build BuildArtifact properties + entry.naming: hash 1`] = `"7gfnt0h6"`;
 
-exports[`Bun.build BuildArtifact properties sourcemap: hash index.js 1`] = `"d1c7nm6t"`;
+exports[`Bun.build BuildArtifact properties sourcemap: hash index.js 1`] = `"est79qzq"`;
 
 exports[`Bun.build BuildArtifact properties sourcemap: hash index.js.map 1`] = `"00000000"`;
 
 exports[`Bun.build new Response(BuildArtifact) sets content type: response text 1`] = `
 "var __defProp = Object.defineProperty;
+var __returnValue = (v) => v;
+function __exportSetter(name, newValue) {
+  this[name] = __returnValue.bind(null, newValue);
+}
 var __export = (target, all) => {
   for (var name in all)
     __defProp(target, name, {
       get: all[name],
       enumerable: true,
       configurable: true,
-      set: (newValue) => all[name] = () => newValue
+      set: __exportSetter.bind(all, name)
     });
 };
 

test/bundler/bundler_edgecase.test.ts

@@ -1113,7 +1113,7 @@ describe("bundler", () => {
     snapshotSourceMap: {
       "entry.js.map": {
         files: ["../node_modules/react/index.js", "../entry.js"],
-        mappingsExactMatch: "qYACA,WAAW,IAAQ,EAAE,ICDrB,eACA,QAAQ,IAAI,CAAK",
+        mappingsExactMatch: "miBACA,WAAW,IAAQ,EAAE,ICDrB,eACA,QAAQ,IAAI,CAAK",
       },
     },
   });

test/bundler/bundler_npm.test.ts

@@ -57,17 +57,17 @@ describe("bundler", () => {
           "../entry.tsx",
         ],
         mappings: [
-          ["react.development.js:524:'getContextName'", "1:5412:Y1"],
+          ["react.development.js:524:'getContextName'", "1:5567:Y1"],
           ["react.development.js:2495:'actScopeDepth'", "23:4082:GJ++"],
-          ["react.development.js:696:''Component'", '1:7474:\'Component "%s"'],
-          ["entry.tsx:6:'\"Content-Type\"'", '100:18809:"Content-Type"'],
-          ["entry.tsx:11:'<html>'", "100:19063:void"],
-          ["entry.tsx:23:'await'", "100:19163:await"],
+          ["react.development.js:696:''Component'", '1:7629:\'Component "%s"'],
+          ["entry.tsx:6:'\"Content-Type\"'", '100:18808:"Content-Type"'],
+          ["entry.tsx:11:'<html>'", "100:19062:void"],
+          ["entry.tsx:23:'await'", "100:19161:await"],
         ],
       },
     },
     expectExactFilesize: {
-      "out/entry.js": 221720,
+      "out/entry.js": 221895,
     },
     run: {
       stdout: "<!DOCTYPE html><html><body><h1>Hello World</h1><p>This is an example.</p></body></html>",

test/bundler/bundler_promiseall_deadcode.test.ts

@@ -76,13 +76,17 @@ describe("bundler", () => {
 
       expect(bundled).toMatchInlineSnapshot(`
         "var __defProp = Object.defineProperty;
+        var __returnValue = (v) => v;
+        function __exportSetter(name, newValue) {
+          this[name] = __returnValue.bind(null, newValue);
+        }
         var __export = (target, all) => {
           for (var name in all)
             __defProp(target, name, {
               get: all[name],
               enumerable: true,
               configurable: true,
-              set: (newValue) => all[name] = () => newValue
+              set: __exportSetter.bind(all, name)
             });
         };
         var __esm = (fn, res) => () => (fn && (res = fn(fn = 0)), res);
@@ -160,7 +164,7 @@ describe("bundler", () => {
         var { AsyncEntryPoint: AsyncEntryPoint2 } = await Promise.resolve().then(() => exports_AsyncEntryPoint);
         AsyncEntryPoint2();
 
-        //# debugId=5E85CC0956C6307964756E2164756E21
+        //# debugId=42062903F19477CF64756E2164756E21
         //# sourceMappingURL=out.js.map
         "
       `);
@@ -337,13 +341,17 @@ describe("bundler", () => {
 
       expect(bundled).toMatchInlineSnapshot(`
         "var __defProp = Object.defineProperty;
+        var __returnValue = (v) => v;
+        function __exportSetter(name, newValue) {
+          this[name] = __returnValue.bind(null, newValue);
+        }
         var __export = (target, all) => {
           for (var name in all)
             __defProp(target, name, {
               get: all[name],
               enumerable: true,
               configurable: true,
-              set: (newValue) => all[name] = () => newValue
+              set: __exportSetter.bind(all, name)
             });
         };
         var __esm = (fn, res) => () => (fn && (res = fn(fn = 0)), res);
@@ -402,7 +410,7 @@ describe("bundler", () => {
         var { AsyncEntryPoint: AsyncEntryPoint2 } = await Promise.resolve().then(() => exports_AsyncEntryPoint);
         AsyncEntryPoint2();
 
-        //# debugId=C92CBF0103732ECC64756E2164756E21
+        //# debugId=BF876FBF618133C264756E2164756E21
         //# sourceMappingURL=out.js.map
         "
       `);

test/bundler/html-import-manifest.test.ts

@@ -103,11 +103,11 @@ console.log(favicon);
             "files": [
               {
                 "input": "client.html",
-                "path": "./client-s249t5qg.js",
+                "path": "./client-b5m4ng86.js",
                 "loader": "js",
                 "isEntry": true,
                 "headers": {
-                  "etag": "fxoJ6L-0X3o",
+                  "etag": "Ax71YVYyZQc",
                   "content-type": "text/javascript;charset=utf-8"
                 }
               },

test/regression/issue/cyclic-imports-async-bundler.test.js

@@ -92,13 +92,17 @@ test("cyclic imports with async dependencies should generate async wrappers", as
 
   expect(bundled).toMatchInlineSnapshot(`
     "var __defProp = Object.defineProperty;
+    var __returnValue = (v) => v;
+    function __exportSetter(name, newValue) {
+      this[name] = __returnValue.bind(null, newValue);
+    }
     var __export = (target, all) => {
       for (var name in all)
         __defProp(target, name, {
           get: all[name],
           enumerable: true,
           configurable: true,
-          set: (newValue) => all[name] = () => newValue
+          set: __exportSetter.bind(all, name)
         });
     };
     var __esm = (fn, res) => () => (fn && (res = fn(fn = 0)), res);
@@ -176,7 +180,7 @@ test("cyclic imports with async dependencies should generate async wrappers", as
     var { AsyncEntryPoint: AsyncEntryPoint2 } = await Promise.resolve().then(() => exports_AsyncEntryPoint);
     AsyncEntryPoint2();
 
-    //# debugId=986E7BD819E590FD64756E2164756E21
+    //# debugId=2020261114B67BB564756E2164756E21
     //# sourceMappingURL=entryBuild.js.map
     "
   `);