Implement Bun.{stdin,stderr,stdout} as LazyProperties to prevent multiple instances (#22291)

## Summary

Previously, accessing `Bun.stdin`, `Bun.stderr`, or `Bun.stdout`
multiple times could potentially create multiple instances within the
same thread, which could lead to memory waste and inconsistent behavior.

This PR implements these properties as LazyProperties on
ZigGlobalObject, ensuring:
- ✅ Single instance per stream per thread
- ✅ Thread-safe lazy initialization using JSC's proven LazyProperty
infrastructure
- ✅ Consistent object identity across multiple accesses 
- ✅ Maintained functionality as Blob objects
- ✅ Memory efficient - objects only created when first accessed

## Implementation Details

### Changes Made:
- **ZigGlobalObject.h**: Added `LazyPropertyOfGlobalObject<JSObject>`
declarations for `m_bunStdin`, `m_bunStderr`, `m_bunStdout` in the GC
member list
- **BunObject.zig**: Created Zig initializer functions
(`createBunStdin`, `createBunStderr`, `createBunStdout`) with proper C
calling convention
- **BunObject.cpp & ZigGlobalObject.cpp**: Added extern C declarations
and C++ wrapper functions that use
`LazyProperty.getInitializedOnMainThread()`
- **ZigGlobalObject.cpp**: Added `initLater()` calls in constructor to
initialize LazyProperties with lambdas that call the Zig functions

### How It Works:
1. When `Bun.stdin` is first accessed, the LazyProperty initializes by
calling our Zig function
2. `getInitializedOnMainThread()` ensures the property is created only
once per thread
3. Subsequent accesses return the cached instance
4. Each stream (stdin/stderr/stdout) gets its own LazyProperty for
distinct instances

## Test Plan

Added comprehensive test coverage in
`test/regression/issue/stdin_stderr_stdout_lazy_property.test.ts`:

✅ **Multiple accesses return identical objects** - Verifies single
instance per thread
```javascript
const stdin1 = Bun.stdin;
const stdin2 = Bun.stdin;
expect(stdin1).toBe(stdin2); // ✅ Same object instance
```

✅ **Objects are distinct from each other** - Each stream has its own
instance
```javascript
expect(Bun.stdin).not.toBe(Bun.stderr); // ✅ Different objects
```

✅ **Functionality preserved** - Still valid Blob objects with all
expected properties

## Testing Results

All tests pass successfully:
```
bun test v1.2.22 (b93468ca)

 3 pass
 0 fail  
 15 expect() calls
Ran 3 tests across 1 file. [2.90s]
```

Manual testing confirms:
- ✅ Multiple property accesses return identical instances 
- ✅ Objects maintain full Blob functionality
- ✅ Each stream has distinct identity (stdin ≠ stderr ≠ stdout)

## Backward Compatibility

This change is fully backward compatible:
- Same API surface
- Same object types (Blob instances)  
- Same functionality and methods
- Only difference: guaranteed single instance per thread (which is the
desired behavior)

🤖 Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>

src/bun.js/api/BunObject.zig

@@ -72,9 +72,6 @@ pub const BunObject = struct {
     pub const inspect = toJSLazyPropertyCallback(Bun.getInspect);
     pub const origin = toJSLazyPropertyCallback(Bun.getOrigin);
     pub const semver = toJSLazyPropertyCallback(Bun.getSemver);
-    pub const stderr = toJSLazyPropertyCallback(Bun.getStderr);
-    pub const stdin = toJSLazyPropertyCallback(Bun.getStdin);
-    pub const stdout = toJSLazyPropertyCallback(Bun.getStdout);
     pub const unsafe = toJSLazyPropertyCallback(Bun.getUnsafe);
     pub const S3Client = toJSLazyPropertyCallback(Bun.getS3ClientConstructor);
     pub const s3 = toJSLazyPropertyCallback(Bun.getS3DefaultClient);
@@ -139,9 +136,6 @@ pub const BunObject = struct {
         @export(&BunObject.hash, .{ .name = lazyPropertyCallbackName("hash") });
         @export(&BunObject.inspect, .{ .name = lazyPropertyCallbackName("inspect") });
         @export(&BunObject.origin, .{ .name = lazyPropertyCallbackName("origin") });
-        @export(&BunObject.stderr, .{ .name = lazyPropertyCallbackName("stderr") });
-        @export(&BunObject.stdin, .{ .name = lazyPropertyCallbackName("stdin") });
-        @export(&BunObject.stdout, .{ .name = lazyPropertyCallbackName("stdout") });
         @export(&BunObject.unsafe, .{ .name = lazyPropertyCallbackName("unsafe") });
         @export(&BunObject.semver, .{ .name = lazyPropertyCallbackName("semver") });
         @export(&BunObject.embeddedFiles, .{ .name = lazyPropertyCallbackName("embeddedFiles") });
@@ -188,6 +182,12 @@ pub const BunObject = struct {
         @export(&BunObject.zstdDecompress, .{ .name = callbackName("zstdDecompress") });
         // --- Callbacks ---
 
+        // --- LazyProperty initializers ---
+        @export(&createBunStdin, .{ .name = "BunObject__createBunStdin" });
+        @export(&createBunStderr, .{ .name = "BunObject__createBunStderr" });
+        @export(&createBunStdout, .{ .name = "BunObject__createBunStdout" });
+        // --- LazyProperty initializers ---
+
         // --- Getters ---
         @export(&BunObject.main, .{ .name = "BunObject_getter_main" });
         // --- Getters ---
@@ -559,39 +559,6 @@ pub fn getOrigin(globalThis: *jsc.JSGlobalObject, _: *jsc.JSObject) jsc.JSValue
     return ZigString.init(VirtualMachine.get().origin.origin).toJS(globalThis);
 }
 
-pub fn getStdin(globalThis: *jsc.JSGlobalObject, _: *jsc.JSObject) jsc.JSValue {
-    var rare_data = globalThis.bunVM().rareData();
-    var store = rare_data.stdin();
-    store.ref();
-    var blob = jsc.WebCore.Blob.new(
-        jsc.WebCore.Blob.initWithStore(store, globalThis),
-    );
-    blob.allocator = bun.default_allocator;
-    return blob.toJS(globalThis);
-}
-
-pub fn getStderr(globalThis: *jsc.JSGlobalObject, _: *jsc.JSObject) jsc.JSValue {
-    var rare_data = globalThis.bunVM().rareData();
-    var store = rare_data.stderr();
-    store.ref();
-    var blob = jsc.WebCore.Blob.new(
-        jsc.WebCore.Blob.initWithStore(store, globalThis),
-    );
-    blob.allocator = bun.default_allocator;
-    return blob.toJS(globalThis);
-}
-
-pub fn getStdout(globalThis: *jsc.JSGlobalObject, _: *jsc.JSObject) jsc.JSValue {
-    var rare_data = globalThis.bunVM().rareData();
-    var store = rare_data.stdout();
-    store.ref();
-    var blob = jsc.WebCore.Blob.new(
-        jsc.WebCore.Blob.initWithStore(store, globalThis),
-    );
-    blob.allocator = bun.default_allocator;
-    return blob.toJS(globalThis);
-}
-
 pub fn enableANSIColors(globalThis: *jsc.JSGlobalObject, _: *jsc.JSObject) jsc.JSValue {
     _ = globalThis;
     return JSValue.jsBoolean(Output.enable_ansi_colors);
@@ -2068,6 +2035,40 @@ comptime {
 
 const string = []const u8;
 
+// LazyProperty initializers for stdin/stderr/stdout
+pub fn createBunStdin(globalThis: *jsc.JSGlobalObject) callconv(.C) jsc.JSValue {
+    var rare_data = globalThis.bunVM().rareData();
+    var store = rare_data.stdin();
+    store.ref();
+    var blob = jsc.WebCore.Blob.new(
+        jsc.WebCore.Blob.initWithStore(store, globalThis),
+    );
+    blob.allocator = bun.default_allocator;
+    return blob.toJS(globalThis);
+}
+
+pub fn createBunStderr(globalThis: *jsc.JSGlobalObject) callconv(.C) jsc.JSValue {
+    var rare_data = globalThis.bunVM().rareData();
+    var store = rare_data.stderr();
+    store.ref();
+    var blob = jsc.WebCore.Blob.new(
+        jsc.WebCore.Blob.initWithStore(store, globalThis),
+    );
+    blob.allocator = bun.default_allocator;
+    return blob.toJS(globalThis);
+}
+
+pub fn createBunStdout(globalThis: *jsc.JSGlobalObject) callconv(.C) jsc.JSValue {
+    var rare_data = globalThis.bunVM().rareData();
+    var store = rare_data.stdout();
+    store.ref();
+    var blob = jsc.WebCore.Blob.new(
+        jsc.WebCore.Blob.initWithStore(store, globalThis),
+    );
+    blob.allocator = bun.default_allocator;
+    return blob.toJS(globalThis);
+}
+
 const Braces = @import("../../shell/braces.zig");
 const Which = @import("../../which.zig");
 const options = @import("../../options.zig");

src/bun.js/bindings/BunObject+exports.h

@@ -31,9 +31,6 @@
     macro(origin) \
     macro(s3) \
     macro(semver) \
-    macro(stderr) \
-    macro(stdin) \
-    macro(stdout) \
     macro(unsafe) \
     macro(valkey) \
 

src/bun.js/bindings/BunObject.cpp

@@ -875,6 +875,25 @@ static JSC_DEFINE_CUSTOM_SETTER(setBunObjectMain, (JSC::JSGlobalObject * globalO
 #define bunObjectReadableStreamToJSONCodeGenerator WebCore::readableStreamReadableStreamToJSONCodeGenerator
 #define bunObjectReadableStreamToTextCodeGenerator WebCore::readableStreamReadableStreamToTextCodeGenerator
 
+// LazyProperty wrappers for stdin/stderr/stdout
+static JSValue BunObject_lazyPropCb_wrap_stdin(VM& vm, JSObject* bunObject)
+{
+    auto* zigGlobalObject = jsCast<Zig::GlobalObject*>(bunObject->globalObject());
+    return zigGlobalObject->m_bunStdin.getInitializedOnMainThread(zigGlobalObject);
+}
+
+static JSValue BunObject_lazyPropCb_wrap_stderr(VM& vm, JSObject* bunObject)
+{
+    auto* zigGlobalObject = jsCast<Zig::GlobalObject*>(bunObject->globalObject());
+    return zigGlobalObject->m_bunStderr.getInitializedOnMainThread(zigGlobalObject);
+}
+
+static JSValue BunObject_lazyPropCb_wrap_stdout(VM& vm, JSObject* bunObject)
+{
+    auto* zigGlobalObject = jsCast<Zig::GlobalObject*>(bunObject->globalObject());
+    return zigGlobalObject->m_bunStdout.getInitializedOnMainThread(zigGlobalObject);
+}
+
 #include "BunObject.lut.h"
 
 #undef bunObjectReadableStreamToArrayCodeGenerator

src/bun.js/bindings/ZigGlobalObject.cpp

@@ -330,6 +330,11 @@ extern "C" void* Bun__getVM();
 
 extern "C" void Bun__setDefaultGlobalObject(Zig::GlobalObject* globalObject);
 
+// Declare the Zig functions for LazyProperty initializers
+extern "C" JSC::EncodedJSValue BunObject__createBunStdin(JSC::JSGlobalObject*);
+extern "C" JSC::EncodedJSValue BunObject__createBunStderr(JSC::JSGlobalObject*);
+extern "C" JSC::EncodedJSValue BunObject__createBunStdout(JSC::JSGlobalObject*);
+
 static JSValue formatStackTraceToJSValue(JSC::VM& vm, Zig::GlobalObject* globalObject, JSC::JSGlobalObject* lexicalGlobalObject, JSC::JSObject* errorObject, JSC::JSArray* callSites)
 {
     auto scope = DECLARE_THROW_SCOPE(vm);
@@ -3463,6 +3468,17 @@ void GlobalObject::finishCreation(VM& vm)
         init.set(JSC::JSBigInt64Array::create(init.owner, JSC::JSBigInt64Array::createStructure(init.vm, init.owner, init.owner->objectPrototype()), 7));
     });
 
+    // Initialize LazyProperties for stdin/stderr/stdout
+    m_bunStdin.initLater([](const LazyProperty<JSC::JSGlobalObject, JSC::JSObject>::Initializer& init) {
+        init.set(JSC::JSValue::decode(BunObject__createBunStdin(init.owner)).getObject());
+    });
+    m_bunStderr.initLater([](const LazyProperty<JSC::JSGlobalObject, JSC::JSObject>::Initializer& init) {
+        init.set(JSC::JSValue::decode(BunObject__createBunStderr(init.owner)).getObject());
+    });
+    m_bunStdout.initLater([](const LazyProperty<JSC::JSGlobalObject, JSC::JSObject>::Initializer& init) {
+        init.set(JSC::JSValue::decode(BunObject__createBunStdout(init.owner)).getObject());
+    });
+
     configureNodeVM(vm, this);
 
 #if ENABLE(REMOTE_INSPECTOR)

src/bun.js/bindings/ZigGlobalObject.h

@@ -621,6 +621,10 @@ public:
     V(public, LazyPropertyOfGlobalObject<Structure>, m_JSBunRequestStructure)                                \
     V(public, LazyPropertyOfGlobalObject<JSObject>, m_JSBunRequestParamsPrototype)                           \
                                                                                                              \
+    V(public, LazyPropertyOfGlobalObject<JSObject>, m_bunStdin)                                              \
+    V(public, LazyPropertyOfGlobalObject<JSObject>, m_bunStderr)                                             \
+    V(public, LazyPropertyOfGlobalObject<JSObject>, m_bunStdout)                                             \
+                                                                                                             \
     V(public, LazyPropertyOfGlobalObject<Structure>, m_JSNodeHTTPServerSocketStructure)                      \
     V(public, LazyPropertyOfGlobalObject<JSFloat64Array>, m_statValues)                                      \
     V(public, LazyPropertyOfGlobalObject<JSBigInt64Array>, m_bigintStatValues)                               \
@@ -654,6 +658,11 @@ public:
 
     JSObject* nodeErrorCache() const { return m_nodeErrorCache.getInitializedOnMainThread(this); }
 
+    // LazyProperty accessors for stdin/stderr/stdout
+    JSC::JSObject* bunStdin() const { return m_bunStdin.getInitializedOnMainThread(this); }
+    JSC::JSObject* bunStderr() const { return m_bunStderr.getInitializedOnMainThread(this); }
+    JSC::JSObject* bunStdout() const { return m_bunStdout.getInitializedOnMainThread(this); }
+
     Structure* memoryFootprintStructure()
     {
         return m_memoryFootprintStructure.getInitializedOnMainThread(this);