Implement virtual module support in `Bun.plugin` (#6167)

* Add support for `build.module` in `Bun.plugin`

* Another test

* Update docs

* Update isBuiltinModule.cpp

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>

17 files changed, 622 insertions, 111 deletions

diff --git a/docs/runtime/plugins.md b/docs/runtime/plugins.md
index f9921cbad..f2e0d7c77 100644
--- a/docs/runtime/plugins.md
+++ b/docs/runtime/plugins.md
@@ -45,7 +45,7 @@ plugin(
 );
 ```
 
-Bun's plugin API is based on [esbuild](https://esbuild.github.io/plugins). Only [a subset](/docs/bundler/vs-esbuild#plugin-api) of the esbuild API is implemented, but some esbuild plugins "just work" in Bun, like the official [MDX loader](https://mdxjs.com/packages/esbuild/):
+Bun's plugin API is loosely based on [esbuild](https://esbuild.github.io/plugins). Only [a subset](/docs/bundler/vs-esbuild#plugin-api) of the esbuild API is implemented, but some esbuild plugins "just work" in Bun, like the official [MDX loader](https://mdxjs.com/packages/esbuild/):
 
 ```jsx
 import { plugin } from "bun";
@@ -217,6 +217,91 @@ import MySvelteComponent from "./component.svelte";
 console.log(mySvelteComponent.render());
 ```
 
+## Virtual Modules
+
+{% note %}
+
+This feature is currently only available at runtime with `Bun.plugin` and not yet supported in the bundler, but you can mimick the behavior using `onResolve` and `onLoad`.
+
+{% /note %}
+
+To create virtual modules at runtime, use `builder.module(specifier, callback)` in the `setup` function of a `Bun.plugin`.
+
+For example:
+
+```js
+import { plugin } from "bun";
+
+plugin({
+  name: "my-virtual-module",
+
+  setup(build) {
+    build.module(
+      // The specifier, which can be any string
+      "my-transpiled-virtual-module",
+      // The callback to run when the module is imported or required for the first time
+      () => {
+        return {
+          contents: "console.log('hello world!')",
+          loader: "js",
+        };
+      },
+    );
+
+    build.module("my-object-virtual-module", () => {
+      return {
+        exports: {
+          foo: "bar",
+        },
+        loader: "object",
+      };
+    });
+  },
+});
+
+// Sometime later
+// All of these work
+import "my-transpiled-virtual-module";
+require("my-transpiled-virtual-module");
+await import("my-transpiled-virtual-module");
+require.resolve("my-transpiled-virtual-module");
+
+import { foo } from "my-object-virtual-module";
+const object = require("my-object-virtual-module");
+await import("my-object-virtual-module");
+require.resolve("my-object-virtual-module");
+```
+
+### Overriding existing modules
+
+You can also override existing modules with `build.module`.
+
+```js
+import { plugin } from "bun";
+build.module("my-object-virtual-module", () => {
+  return {
+    exports: {
+      foo: "bar",
+    },
+    loader: "object",
+  };
+});
+
+require("my-object-virtual-module"); // { foo: "bar" }
+await import("my-object-virtual-module"); // { foo: "bar" }
+
+build.module("my-object-virtual-module", () => {
+  return {
+    exports: {
+      baz: "quix",
+    },
+    loader: "object",
+  };
+});
+require("my-object-virtual-module"); // { baz: "quix" }
+await import("my-object-virtual-module"); // { baz: "quix" }
+```
+
 ## Reading the config
 
 Plugins can read and write to the [build config](/docs/bundler#api) with `build.config`.
diff --git a/packages/bun-types/bun.d.ts b/packages/bun-types/bun.d.ts
index 514a6bbdb..9b2d314e8 100644
--- a/packages/bun-types/bun.d.ts
+++ b/packages/bun-types/bun.d.ts
@@ -3293,6 +3293,37 @@ declare module "bun" {
      * The config object passed to `Bun.build` as is. Can be mutated.
      */
     config: BuildConfig & { plugins: BunPlugin[] };
+
+    /**
+     * Create a lazy-loaded virtual module that can be `import`ed or `require`d from other modules
+     *
+     * @param specifier The module specifier to register the callback for
+     * @param callback The function to run when the module is imported or required
+     *
+     * ### Example
+     * @example
+     * ```ts
+     * Bun.plugin({
+     *   setup(builder) {
+     *     builder.module("hello:world", () => {
+     *       return { exports: { foo: "bar" }, loader: "object" };
+     *     });
+     *   },
+     * });
+     *
+     * // sometime later
+     * const { foo } = await import("hello:world");
+     * console.log(foo); // "bar"
+     *
+     * // or
+     * const { foo } = require("hello:world");
+     * console.log(foo); // "bar"
+     * ```
+     */
+    module(
+      specifier: string,
+      callback: () => OnLoadResult | Promise<OnLoadResult>,
+    ): void;
   }
 
   interface BunPlugin {
diff --git a/src/bun.js/bindings/BunPlugin.cpp b/src/bun.js/bindings/BunPlugin.cpp
index 129d7816b..b53fcf313 100644
--- a/src/bun.js/bindings/BunPlugin.cpp
+++ b/src/bun.js/bindings/BunPlugin.cpp
@@ -17,8 +17,10 @@
 #include "JavaScriptCore/RegExpObject.h"
 #include "JavaScriptCore/JSPromise.h"
 #include "BunClientData.h"
-
+#include "isBuiltinModule.h"
 #include "JavaScriptCore/RegularExpression.h"
+#include "JavaScriptCore/JSMap.h"
+#include "JavaScriptCore/JSMapInlines.h"
 
 namespace Zig {
 
@@ -86,6 +88,76 @@ static EncodedJSValue jsFunctionAppendOnLoadPluginBody(JSC::JSGlobalObject* glob
     return JSValue::encode(jsUndefined());
 }
 
+static EncodedJSValue jsFunctionAppendVirtualModulePluginBody(JSC::JSGlobalObject* globalObject, JSC::CallFrame* callframe)
+{
+    JSC::VM& vm = globalObject->vm();
+    auto scope = DECLARE_THROW_SCOPE(vm);
+
+    if (callframe->argumentCount() < 2) {
+        throwException(globalObject, scope, createError(globalObject, "module() needs 2 arguments: a module ID and a function to call"_s));
+        return JSValue::encode(jsUndefined());
+    }
+
+    JSValue moduleIdValue = callframe->uncheckedArgument(0);
+    JSValue functionValue = callframe->uncheckedArgument(1);
+
+    if (!moduleIdValue.isString()) {
+        throwException(globalObject, scope, createError(globalObject, "module() expects first argument to be a string for the module ID"_s));
+        return JSValue::encode(jsUndefined());
+    }
+
+    if (!functionValue.isCallable()) {
+        throwException(globalObject, scope, createError(globalObject, "module() expects second argument to be a function"_s));
+        return JSValue::encode(jsUndefined());
+    }
+
+    String moduleId = moduleIdValue.toWTFString(globalObject);
+    RETURN_IF_EXCEPTION(scope, encodedJSValue());
+
+    if (moduleId.isEmpty()) {
+        throwException(globalObject, scope, createError(globalObject, "virtual module cannot be blank"_s));
+        return JSValue::encode(jsUndefined());
+    }
+
+    if (Bun::isBuiltinModule(moduleId)) {
+        throwException(globalObject, scope, createError(globalObject, makeString("module() cannot be used to override builtin module \""_s, moduleId, "\""_s)));
+        return JSValue::encode(jsUndefined());
+    }
+
+    if (moduleId.startsWith("."_s)) {
+        throwException(globalObject, scope, createError(globalObject, "virtual module cannot start with \".\""_s));
+        return JSValue::encode(jsUndefined());
+    }
+
+    Zig::GlobalObject* global = Zig::jsCast<Zig::GlobalObject*>(globalObject);
+    if (global->onLoadPlugins.virtualModules == nullptr) {
+        global->onLoadPlugins.virtualModules = new BunPlugin::VirtualModuleMap;
+    }
+    auto* virtualModules = global->onLoadPlugins.virtualModules;
+
+    virtualModules->set(moduleId, JSC::Strong<JSC::JSObject> { vm, jsCast<JSC::JSObject*>(functionValue) });
+
+    JSMap* esmRegistry;
+
+    if (auto loaderValue = global->getIfPropertyExists(global, JSC::Identifier::fromString(vm, "Loader"_s))) {
+        if (auto registryValue = loaderValue.getObject()->getIfPropertyExists(global, JSC::Identifier::fromString(vm, "registry"_s))) {
+            esmRegistry = jsCast<JSC::JSMap*>(registryValue);
+        }
+    }
+
+    global->requireMap()->remove(globalObject, moduleIdValue);
+    esmRegistry && esmRegistry->remove(globalObject, moduleIdValue);
+
+    // bool hasBeenRequired = global->requireMap()->has(globalObject, moduleIdValue);
+    // bool hasBeenImported = esmRegistry && esmRegistry->has(globalObject, moduleIdValue);
+    // if (hasBeenRequired || hasBeenImported) {
+    //     // callAndReplaceModule(global, moduleIdValue, functionValue, global->requireMap(), esmRegistry, hasBeenRequired, hasBeenImported);
+    //     // RETURN_IF_EXCEPTION(scope, encodedJSValue());
+    // }
+
+    return JSValue::encode(jsUndefined());
+}
+
 static EncodedJSValue jsFunctionAppendOnResolvePluginBody(JSC::JSGlobalObject* globalObject, JSC::CallFrame* callframe, BunPluginTarget target, BunPlugin::Base& plugin, void* ctx, OnAppendPluginCallback callback)
 {
     JSC::VM& vm = globalObject->vm();
@@ -143,7 +215,7 @@ static EncodedJSValue jsFunctionAppendOnResolvePluginGlobal(JSC::JSGlobalObject*
 {
     Zig::GlobalObject* global = Zig::jsCast<Zig::GlobalObject*>(globalObject);
 
-    auto& plugins = global->onResolvePlugins[target];
+    auto& plugins = global->onResolvePlugins;
     auto callback = Bun__onDidAppendPlugin;
     return jsFunctionAppendOnResolvePluginBody(globalObject, callframe, target, plugins, global->bunVM(), callback);
 }
@@ -152,7 +224,7 @@ static EncodedJSValue jsFunctionAppendOnLoadPluginGlobal(JSC::JSGlobalObject* gl
 {
     Zig::GlobalObject* global = Zig::jsCast<Zig::GlobalObject*>(globalObject);
 
-    auto& plugins = global->onLoadPlugins[target];
+    auto& plugins = global->onLoadPlugins;
     auto callback = Bun__onDidAppendPlugin;
     return jsFunctionAppendOnLoadPluginBody(globalObject, callframe, target, plugins, global->bunVM(), callback);
 }
@@ -182,6 +254,11 @@ JSC_DEFINE_HOST_FUNCTION(jsFunctionAppendOnResolvePluginBun, (JSC::JSGlobalObjec
     return jsFunctionAppendOnResolvePluginGlobal(globalObject, callframe, BunPluginTargetBun);
 }
 
+JSC_DEFINE_HOST_FUNCTION(jsFunctionAppendVirtualModule, (JSC::JSGlobalObject * globalObject, JSC::CallFrame* callframe))
+{
+    return jsFunctionAppendVirtualModulePluginBody(globalObject, callframe);
+}
+
 JSC_DEFINE_HOST_FUNCTION(jsFunctionAppendOnResolvePluginBrowser, (JSC::JSGlobalObject * globalObject, JSC::CallFrame* callframe))
 {
     return jsFunctionAppendOnResolvePluginGlobal(globalObject, callframe, BunPluginTargetBrowser);
@@ -190,12 +267,12 @@ JSC_DEFINE_HOST_FUNCTION(jsFunctionAppendOnResolvePluginBrowser, (JSC::JSGlobalO
 extern "C" EncodedJSValue jsFunctionBunPluginClear(JSC::JSGlobalObject* globalObject, JSC::CallFrame* callframe)
 {
     Zig::GlobalObject* global = reinterpret_cast<Zig::GlobalObject*>(globalObject);
-    for (uint8_t i = 0; i < BunPluginTargetMax + 1; i++) {
-        global->onLoadPlugins[i].fileNamespace.clear();
-        global->onResolvePlugins[i].fileNamespace.clear();
-        global->onLoadPlugins[i].groups.clear();
-        global->onResolvePlugins[i].namespaces.clear();
-    }
+    global->onLoadPlugins.fileNamespace.clear();
+    global->onResolvePlugins.fileNamespace.clear();
+    global->onLoadPlugins.groups.clear();
+    global->onResolvePlugins.namespaces.clear();
+
+    delete global->onLoadPlugins.virtualModules;
 
     return JSValue::encode(jsUndefined());
 }
@@ -239,76 +316,37 @@ extern "C" EncodedJSValue setupBunPlugin(JSC::JSGlobalObject* globalObject, JSC:
     }
 
     JSFunction* setupFunction = jsCast<JSFunction*>(setupFunctionValue);
-    JSObject* builderObject = JSC::constructEmptyObject(globalObject, globalObject->objectPrototype(), 3);
-
-    switch (target) {
-    case BunPluginTargetNode: {
-        builderObject->putDirect(vm, Identifier::fromString(vm, "target"_s), jsString(vm, String("node"_s)), 0);
-        builderObject->putDirectNativeFunction(
-            vm,
-            globalObject,
-            JSC::Identifier::fromString(vm, "onLoad"_s),
-            1,
-            jsFunctionAppendOnLoadPluginNode,
-            ImplementationVisibility::Public,
-            NoIntrinsic,
-            JSC::PropertyAttribute::DontDelete | 0);
-        builderObject->putDirectNativeFunction(
-            vm,
-            globalObject,
-            JSC::Identifier::fromString(vm, "onResolve"_s),
-            1,
-            jsFunctionAppendOnResolvePluginNode,
-            ImplementationVisibility::Public,
-            NoIntrinsic,
-            JSC::PropertyAttribute::DontDelete | 0);
-        break;
-    }
-    case BunPluginTargetBun: {
-        builderObject->putDirect(vm, Identifier::fromString(vm, "target"_s), jsString(vm, String("bun"_s)), 0);
-        builderObject->putDirectNativeFunction(
-            vm,
-            globalObject,
-            JSC::Identifier::fromString(vm, "onLoad"_s),
-            1,
-            jsFunctionAppendOnLoadPluginBun,
-            ImplementationVisibility::Public,
-            NoIntrinsic,
-            JSC::PropertyAttribute::DontDelete | 0);
-        builderObject->putDirectNativeFunction(
-            vm,
-            globalObject,
-            JSC::Identifier::fromString(vm, "onResolve"_s),
-            1,
-            jsFunctionAppendOnResolvePluginBun,
-            ImplementationVisibility::Public,
-            NoIntrinsic,
-            JSC::PropertyAttribute::DontDelete | 0);
-        break;
-    }
-    case BunPluginTargetBrowser: {
-        builderObject->putDirect(vm, Identifier::fromString(vm, "target"_s), jsString(vm, String("browser"_s)), 0);
-        builderObject->putDirectNativeFunction(
-            vm,
-            globalObject,
-            JSC::Identifier::fromString(vm, "onLoad"_s),
-            1,
-            jsFunctionAppendOnLoadPluginBrowser,
-            ImplementationVisibility::Public,
-            NoIntrinsic,
-            JSC::PropertyAttribute::DontDelete | 0);
-        builderObject->putDirectNativeFunction(
-            vm,
-            globalObject,
-            JSC::Identifier::fromString(vm, "onResolve"_s),
-            1,
-            jsFunctionAppendOnResolvePluginBrowser,
-            ImplementationVisibility::Public,
-            NoIntrinsic,
-            JSC::PropertyAttribute::DontDelete | 0);
-        break;
-    }
-    }
+    JSObject* builderObject = JSC::constructEmptyObject(globalObject, globalObject->objectPrototype(), 4);
+
+    builderObject->putDirect(vm, Identifier::fromString(vm, "target"_s), jsString(vm, String("bun"_s)), 0);
+    builderObject->putDirectNativeFunction(
+        vm,
+        globalObject,
+        JSC::Identifier::fromString(vm, "onLoad"_s),
+        1,
+        jsFunctionAppendOnLoadPluginBun,
+        ImplementationVisibility::Public,
+        NoIntrinsic,
+        JSC::PropertyAttribute::DontDelete | 0);
+    builderObject->putDirectNativeFunction(
+        vm,
+        globalObject,
+        JSC::Identifier::fromString(vm, "onResolve"_s),
+        1,
+        jsFunctionAppendOnResolvePluginBun,
+        ImplementationVisibility::Public,
+        NoIntrinsic,
+        JSC::PropertyAttribute::DontDelete | 0);
+
+    builderObject->putDirectNativeFunction(
+        vm,
+        globalObject,
+        JSC::Identifier::fromString(vm, "module"_s),
+        1,
+        jsFunctionAppendVirtualModule,
+        ImplementationVisibility::Public,
+        NoIntrinsic,
+        JSC::PropertyAttribute::DontDelete | 0);
 
     JSC::MarkedArgumentBuffer args;
     args.append(builderObject);
@@ -329,9 +367,7 @@ extern "C" EncodedJSValue setupBunPlugin(JSC::JSGlobalObject* globalObject, JSC:
 extern "C" EncodedJSValue jsFunctionBunPlugin(JSC::JSGlobalObject* globalObject, JSC::CallFrame* callframe)
 {
     Zig::GlobalObject* global = reinterpret_cast<Zig::GlobalObject*>(globalObject);
-    BunPluginTarget target = global->defaultBunPluginTarget;
-
-    return setupBunPlugin(globalObject, callframe, target);
+    return setupBunPlugin(globalObject, callframe, BunPluginTargetBun);
 }
 
 void BunPlugin::Group::append(JSC::VM& vm, JSC::RegExp* filter, JSC::JSFunction* func)
@@ -513,10 +549,60 @@ EncodedJSValue BunPlugin::OnResolve::run(JSC::JSGlobalObject* globalObject, BunS
 
 extern "C" JSC::EncodedJSValue Bun__runOnResolvePlugins(Zig::GlobalObject* globalObject, BunString* namespaceString, BunString* path, BunString* from, BunPluginTarget target)
 {
-    return globalObject->onResolvePlugins[target].run(globalObject, namespaceString, path, from);
+    return globalObject->onResolvePlugins.run(globalObject, namespaceString, path, from);
 }
 
 extern "C" JSC::EncodedJSValue Bun__runOnLoadPlugins(Zig::GlobalObject* globalObject, BunString* namespaceString, BunString* path, BunPluginTarget target)
 {
-    return globalObject->onLoadPlugins[target].run(globalObject, namespaceString, path);
+    return globalObject->onLoadPlugins.run(globalObject, namespaceString, path);
+}
+
+namespace Bun {
+JSC::JSValue runVirtualModule(Zig::GlobalObject* globalObject, BunString* specifier)
+{
+    auto fallback = [&]() -> JSC::JSValue {
+        return JSValue::decode(Bun__runVirtualModule(globalObject, specifier));
+    };
+
+    if (!globalObject->onLoadPlugins.virtualModules) {
+        return fallback();
+    }
+    auto& virtualModules = *globalObject->onLoadPlugins.virtualModules;
+    WTF::String specifierString = Bun::toWTFString(*specifier);
+    if (auto virtualModuleFn = virtualModules.get(specifierString)) {
+        auto& vm = globalObject->vm();
+        JSC::JSObject* function = virtualModuleFn.get();
+        auto throwScope = DECLARE_THROW_SCOPE(vm);
+
+        JSC::MarkedArgumentBuffer arguments;
+        JSC::CallData callData = JSC::getCallData(function);
+        RELEASE_ASSERT(callData.type != JSC::CallData::Type::None);
+
+        auto result = call(globalObject, function, callData, JSC::jsUndefined(), arguments);
+        RETURN_IF_EXCEPTION(throwScope, JSC::jsUndefined());
+
+        if (auto* promise = JSC::jsDynamicCast<JSPromise*>(result)) {
+            switch (promise->status(vm)) {
+            case JSPromise::Status::Rejected:
+            case JSPromise::Status::Pending: {
+                return promise;
+            }
+            case JSPromise::Status::Fulfilled: {
+                result = promise->result(vm);
+                break;
+            }
+            }
+        }
+
+        if (!result.isObject()) {
+            JSC::throwTypeError(globalObject, throwScope, "virtual module expects an object returned"_s);
+            return JSC::jsUndefined();
+        }
+
+        return result;
+    }
+
+    return fallback();
 }
+
+}
\ No newline at end of file
diff --git a/src/bun.js/bindings/BunPlugin.h b/src/bun.js/bindings/BunPlugin.h
index cf37b739b..f4d09883d 100644
--- a/src/bun.js/bindings/BunPlugin.h
+++ b/src/bun.js/bindings/BunPlugin.h
@@ -15,6 +15,8 @@ using namespace JSC;
 
 class BunPlugin {
 public:
+    using VirtualModuleMap = WTF::HashMap<String, JSC::Strong<JSC::JSObject>>;
+
     // This is a list of pairs of regexps and functions to match against
     class Group {
 
@@ -67,7 +69,15 @@ public:
         {
         }
 
-        EncodedJSValue run(JSC::JSGlobalObject* globalObject, BunString* namespaceString, BunString* path);
+        VirtualModuleMap* virtualModules = nullptr;
+        JSC::EncodedJSValue run(JSC::JSGlobalObject* globalObject, BunString* namespaceString, BunString* path);
+
+        ~OnLoad()
+        {
+            if (virtualModules) {
+                delete virtualModules;
+            }
+        }
     };
 
     class OnResolve final : public Base {
@@ -78,8 +88,14 @@ public:
         {
         }
 
-        EncodedJSValue run(JSC::JSGlobalObject* globalObject, BunString* namespaceString, BunString* path, BunString* importer);
+        JSC::EncodedJSValue run(JSC::JSGlobalObject* globalObject, BunString* namespaceString, BunString* path, BunString* importer);
     };
 };
 
-} // namespace Zig
\ No newline at end of file
+class GlobalObject;
+
+} // namespace Zig
+
+namespace Bun {
+JSC::JSValue runVirtualModule(Zig::GlobalObject*, BunString* specifier);
+}
\ No newline at end of file
diff --git a/src/bun.js/bindings/ImportMetaObject.cpp b/src/bun.js/bindings/ImportMetaObject.cpp
index 4160102a5..340c3319b 100644
--- a/src/bun.js/bindings/ImportMetaObject.cpp
+++ b/src/bun.js/bindings/ImportMetaObject.cpp
@@ -64,6 +64,12 @@ static EncodedJSValue functionRequireResolve(JSC::JSGlobalObject* globalObject,
         JSC::JSValue moduleName = callFrame->argument(0);
 
         auto doIt = [&](const WTF::String& fromStr) -> JSC::EncodedJSValue {
+            if (auto* virtualModules = jsCast<Zig::GlobalObject*>(globalObject)->onLoadPlugins.virtualModules) {
+                if (virtualModules->contains(fromStr)) {
+                    return JSC::JSValue::encode(jsString(vm, fromStr));
+                }
+            }
+
             BunString from = Bun::toString(fromStr);
             auto result = Bun__resolveSyncWithSource(globalObject, JSC::JSValue::encode(moduleName), &from, false);
 
@@ -160,6 +166,14 @@ extern "C" EncodedJSValue functionImportMeta__resolveSync(JSC::JSGlobalObject* g
     JSC__JSValue from;
     bool isESM = true;
 
+    if (auto* virtualModules = jsCast<Zig::GlobalObject*>(globalObject)->onLoadPlugins.virtualModules) {
+        if (moduleName.isString()) {
+            if (virtualModules->contains(moduleName.toWTFString(globalObject))) {
+                return JSC::JSValue::encode(moduleName);
+            }
+        }
+    }
+
     if (callFrame->argumentCount() > 1) {
 
         if (callFrame->argumentCount() > 2) {
@@ -226,6 +240,7 @@ extern "C" EncodedJSValue functionImportMeta__resolveSyncPrivate(JSC::JSGlobalOb
 {
     JSC::VM& vm = globalObject->vm();
     auto scope = DECLARE_THROW_SCOPE(globalObject->vm());
+    auto* global = jsDynamicCast<Zig::GlobalObject*>(globalObject);
 
     JSC::JSValue moduleName = callFrame->argument(0);
     JSValue from = callFrame->argument(1);
@@ -239,8 +254,15 @@ extern "C" EncodedJSValue functionImportMeta__resolveSyncPrivate(JSC::JSGlobalOb
 
     RETURN_IF_EXCEPTION(scope, JSC::JSValue::encode(JSC::JSValue {}));
 
+    if (auto* virtualModules = global->onLoadPlugins.virtualModules) {
+        if (moduleName.isString()) {
+            if (virtualModules->contains(moduleName.toWTFString(globalObject))) {
+                return JSC::JSValue::encode(moduleName);
+            }
+        }
+    }
+
     if (!isESM) {
-        auto* global = jsDynamicCast<Zig::GlobalObject*>(globalObject);
         if (LIKELY(global)) {
             auto overrideHandler = global->m_nodeModuleOverriddenResolveFilename.get();
             if (UNLIKELY(overrideHandler)) {
@@ -289,6 +311,14 @@ JSC_DEFINE_HOST_FUNCTION(functionImportMeta__resolve,
 
         JSC__JSValue from;
 
+        if (auto* virtualModules = jsCast<Zig::GlobalObject*>(globalObject)->onLoadPlugins.virtualModules) {
+            if (moduleName.isString()) {
+                if (virtualModules->contains(moduleName.toWTFString(globalObject))) {
+                    return JSC::JSValue::encode(moduleName);
+                }
+            }
+        }
+
         if (callFrame->argumentCount() > 1 && callFrame->argument(1).isString()) {
             from = JSC::JSValue::encode(callFrame->argument(1));
         } else {
diff --git a/src/bun.js/bindings/JSBundlerPlugin.cpp b/src/bun.js/bindings/JSBundlerPlugin.cpp
index 6ae266df7..d896d5b3d 100644
--- a/src/bun.js/bindings/JSBundlerPlugin.cpp
+++ b/src/bun.js/bindings/JSBundlerPlugin.cpp
@@ -31,6 +31,7 @@ namespace Bun {
 extern "C" void JSBundlerPlugin__addError(void*, void*, JSC::EncodedJSValue, JSC::EncodedJSValue);
 extern "C" void JSBundlerPlugin__onLoadAsync(void*, void*, JSC::EncodedJSValue, JSC::EncodedJSValue);
 extern "C" void JSBundlerPlugin__onResolveAsync(void*, void*, JSC::EncodedJSValue, JSC::EncodedJSValue, JSC::EncodedJSValue);
+extern "C" void JSBundlerPlugin__onVirtualModulePlugin(void*, void*, JSC::EncodedJSValue, JSC::EncodedJSValue, JSC::EncodedJSValue);
 
 JSC_DECLARE_HOST_FUNCTION(jsBundlerPluginFunction_addFilter);
 JSC_DECLARE_HOST_FUNCTION(jsBundlerPluginFunction_addError);
@@ -154,6 +155,7 @@ public:
     Bun::BundlerPlugin plugin;
     JSC::LazyProperty<JSBundlerPlugin, JSC::JSFunction> onLoadFunction;
     JSC::LazyProperty<JSBundlerPlugin, JSC::JSFunction> onResolveFunction;
+    JSC::LazyProperty<JSBundlerPlugin, JSC::JSFunction> moduleFunction;
     JSC::LazyProperty<JSBundlerPlugin, JSC::JSFunction> setupFunction;
 
 private:
diff --git a/src/bun.js/bindings/ModuleLoader.cpp b/src/bun.js/bindings/ModuleLoader.cpp
index acda70e0a..127fb6965 100644
--- a/src/bun.js/bindings/ModuleLoader.cpp
+++ b/src/bun.js/bindings/ModuleLoader.cpp
@@ -458,7 +458,7 @@ JSValue fetchCommonJSModule(
         }
     }
 
-    if (JSC::JSValue virtualModuleResult = JSValue::decode(Bun__runVirtualModule(globalObject, specifier))) {
+    if (JSC::JSValue virtualModuleResult = Bun::runVirtualModule(globalObject, specifier)) {
         JSPromise* promise = jsCast<JSPromise*>(handleVirtualModuleResult<true>(globalObject, virtualModuleResult, res, specifier, referrer));
         switch (promise->status(vm)) {
         case JSPromise::Status::Rejected: {
@@ -633,7 +633,7 @@ static JSValue fetchESMSourceCode(
         }
     }
 
-    if (JSC::JSValue virtualModuleResult = JSValue::decode(Bun__runVirtualModule(globalObject, specifier))) {
+    if (JSC::JSValue virtualModuleResult = Bun::runVirtualModule(globalObject, specifier)) {
         return handleVirtualModuleResult<allowPromise>(globalObject, virtualModuleResult, res, specifier, referrer);
     }
 
diff --git a/src/bun.js/bindings/ZigGlobalObject.cpp b/src/bun.js/bindings/ZigGlobalObject.cpp
index d54800ca6..b9f2e4e46 100644
--- a/src/bun.js/bindings/ZigGlobalObject.cpp
+++ b/src/bun.js/bindings/ZigGlobalObject.cpp
@@ -4036,12 +4036,24 @@ extern "C" void JSC__JSGlobalObject__queueMicrotaskCallback(Zig::GlobalObject* g
     globalObject->queueMicrotask(function, JSValue(bitwise_cast<double>(reinterpret_cast<uintptr_t>(ptr))), JSValue(bitwise_cast<double>(reinterpret_cast<uintptr_t>(callback))), jsUndefined(), jsUndefined());
 }
 
-JSC::Identifier GlobalObject::moduleLoaderResolve(JSGlobalObject* globalObject,
+JSC::Identifier GlobalObject::moduleLoaderResolve(JSGlobalObject* jsGlobalObject,
     JSModuleLoader* loader, JSValue key,
     JSValue referrer, JSValue origin)
 {
+    Zig::GlobalObject* globalObject = reinterpret_cast<Zig::GlobalObject*>(jsGlobalObject);
+
     ErrorableString res;
     res.success = false;
+
+    if (key.isString()) {
+        if (auto* virtualModules = globalObject->onLoadPlugins.virtualModules) {
+            auto keyString = key.toWTFString(globalObject);
+            if (virtualModules->contains(keyString)) {
+                return JSC::Identifier::fromString(globalObject->vm(), keyString);
+            }
+        }
+    }
+
     BunString keyZ;
     if (key.isString()) {
         auto moduleName = jsCast<JSString*>(key)->value(globalObject);
@@ -4077,18 +4089,32 @@ JSC::Identifier GlobalObject::moduleLoaderResolve(JSGlobalObject* globalObject,
     }
 }
 
-JSC::JSInternalPromise* GlobalObject::moduleLoaderImportModule(JSGlobalObject* globalObject,
+JSC::JSInternalPromise* GlobalObject::moduleLoaderImportModule(JSGlobalObject* jsGlobalObject,
     JSModuleLoader*,
     JSString* moduleNameValue,
     JSValue parameters,
     const SourceOrigin& sourceOrigin)
 {
+    auto* globalObject = reinterpret_cast<Zig::GlobalObject*>(jsGlobalObject);
     JSC::VM& vm = globalObject->vm();
     auto scope = DECLARE_THROW_SCOPE(vm);
 
     auto* promise = JSC::JSInternalPromise::create(vm, globalObject->internalPromiseStructure());
     RETURN_IF_EXCEPTION(scope, promise->rejectWithCaughtException(globalObject, scope));
 
+    if (auto* virtualModules = globalObject->onLoadPlugins.virtualModules) {
+        auto keyString = moduleNameValue->value(globalObject);
+        if (virtualModules->contains(keyString)) {
+            auto resolvedIdentifier = JSC::Identifier::fromString(vm, keyString);
+
+            auto result = JSC::importModule(globalObject, resolvedIdentifier,
+                JSC::jsUndefined(), parameters, JSC::jsUndefined());
+
+            RETURN_IF_EXCEPTION(scope, promise->rejectWithCaughtException(globalObject, scope));
+            return result;
+        }
+    }
+
     auto sourceURL = sourceOrigin.url();
     ErrorableString resolved;
     BunString moduleNameZ;
diff --git a/src/bun.js/bindings/ZigGlobalObject.h b/src/bun.js/bindings/ZigGlobalObject.h
index 26111725b..035d18b08 100644
--- a/src/bun.js/bindings/ZigGlobalObject.h
+++ b/src/bun.js/bindings/ZigGlobalObject.h
@@ -382,9 +382,8 @@ public:
         return false;
     }
 
-    BunPlugin::OnLoad onLoadPlugins[BunPluginTargetMax + 1] {};
-    BunPlugin::OnResolve onResolvePlugins[BunPluginTargetMax + 1] {};
-    BunPluginTarget defaultBunPluginTarget = BunPluginTargetBun;
+    BunPlugin::OnLoad onLoadPlugins {};
+    BunPlugin::OnResolve onResolvePlugins {};
 
     // This increases the cache hit rate for JSC::VM's SourceProvider cache
     // It also avoids an extra allocation for the SourceProvider
diff --git a/src/bun.js/bindings/isBuiltinModule.cpp b/src/bun.js/bindings/isBuiltinModule.cpp
new file mode 100644
index 000000000..b8e69f479
--- /dev/null
+++ b/src/bun.js/bindings/isBuiltinModule.cpp
@@ -0,0 +1,98 @@
+#include "root.h"
+
+static constexpr ASCIILiteral builtinModuleNamesSortedLength[] = {
+    "fs"_s,
+    "os"_s,
+    "v8"_s,
+    "vm"_s,
+    "ws"_s,
+    "bun"_s,
+    "dns"_s,
+    "net"_s,
+    "sys"_s,
+    "tls"_s,
+    "tty"_s,
+    "url"_s,
+    "http"_s,
+    "path"_s,
+    "repl"_s,
+    "util"_s,
+    "wasi"_s,
+    "zlib"_s,
+    "dgram"_s,
+    "http2"_s,
+    "https"_s,
+    "assert"_s,
+    "buffer"_s,
+    "crypto"_s,
+    "domain"_s,
+    "events"_s,
+    "module"_s,
+    "stream"_s,
+    "timers"_s,
+    "undici"_s,
+    "bun:ffi"_s,
+    "bun:jsc"_s,
+    "cluster"_s,
+    "console"_s,
+    "process"_s,
+    "bun:wrap"_s,
+    "punycode"_s,
+    "bun:test"_s,
+    "bun:main"_s,
+    "readline"_s,
+    "_tls_wrap"_s,
+    "constants"_s,
+    "inspector"_s,
+    "bun:sqlite"_s,
+    "path/posix"_s,
+    "path/win32"_s,
+    "perf_hooks"_s,
+    "stream/web"_s,
+    "util/types"_s,
+    "_http_agent"_s,
+    "_tls_common"_s,
+    "async_hooks"_s,
+    "detect-libc"_s,
+    "fs/promises"_s,
+    "querystring"_s,
+    "_http_client"_s,
+    "_http_common"_s,
+    "_http_server"_s,
+    "_stream_wrap"_s,
+    "dns/promises"_s,
+    "trace_events"_s,
+    "assert/strict"_s,
+    "child_process"_s,
+    "_http_incoming"_s,
+    "_http_outgoing"_s,
+    "_stream_duplex"_s,
+    "string_decoder"_s,
+    "worker_threads"_s,
+    "stream/promises"_s,
+    "timers/promises"_s,
+    "_stream_readable"_s,
+    "_stream_writable"_s,
+    "stream/consumers"_s,
+    "_stream_transform"_s,
+    "readline/promises"_s,
+    "inspector/promises"_s,
+    "_stream_passthrough"_s,
+    "diagnostics_channel"_s,
+};
+
+namespace Bun {
+
+bool isBuiltinModule(const String &namePossiblyWithNodePrefix) {
+  String name = namePossiblyWithNodePrefix;
+  if (name.startsWith("node:"_s))
+    name = name.substringSharingImpl(5);
+
+  for (auto &builtinModule : builtinModuleNamesSortedLength) {
+    if (name == builtinModule)
+      return true;
+  }
+  return false;
+}
+
+} // namespace Bun
\ No newline at end of file
diff --git a/src/bun.js/bindings/isBuiltinModule.h b/src/bun.js/bindings/isBuiltinModule.h
new file mode 100644
index 000000000..d66f025d1
--- /dev/null
+++ b/src/bun.js/bindings/isBuiltinModule.h
@@ -0,0 +1,5 @@
+#pragma once
+
+namespace Bun {
+bool isBuiltinModule(const String &namePossiblyWithNodePrefix);
+} // namespace Bun
\ No newline at end of file
diff --git a/src/bun.js/modules/NodeModuleModule.h b/src/bun.js/modules/NodeModuleModule.h
index ddb273de4..0da967f65 100644
--- a/src/bun.js/modules/NodeModuleModule.h
+++ b/src/bun.js/modules/NodeModuleModule.h
@@ -1,8 +1,11 @@
+#pragma once
+
 #include "CommonJSModuleRecord.h"
 #include "ImportMetaObject.h"
 #include "JavaScriptCore/JSBoundFunction.h"
 #include "JavaScriptCore/ObjectConstructor.h"
 #include "_NativeModule.h"
+#include "isBuiltinModule.h"
 
 using namespace Zig;
 using namespace JSC;
@@ -88,18 +91,6 @@ static constexpr ASCIILiteral builtinModuleNames[] = {
     "zlib"_s,
 };
 
-static bool isBuiltinModule(const String &namePossiblyWithNodePrefix) {
-  String name = namePossiblyWithNodePrefix;
-  if (name.startsWith("node:"_s))
-    name = name.substringSharingImpl(5);
-
-  for (auto &builtinModule : builtinModuleNames) {
-    if (name == builtinModule)
-      return true;
-  }
-  return false;
-}
-
 JSC_DEFINE_HOST_FUNCTION(jsFunctionNodeModuleModuleConstructor,
                          (JSC::JSGlobalObject * globalObject,
                           JSC::CallFrame *callFrame)) {
@@ -158,7 +149,7 @@ JSC_DEFINE_HOST_FUNCTION(jsFunctionIsBuiltinModule,
   auto moduleStr = moduleName.toWTFString(globalObject);
   RETURN_IF_EXCEPTION(scope, JSValue::encode(jsBoolean(false)));
 
-  return JSValue::encode(jsBoolean(isBuiltinModule(moduleStr)));
+  return JSValue::encode(jsBoolean(Bun::isBuiltinModule(moduleStr)));
 }
 
 JSC_DEFINE_HOST_FUNCTION(jsFunctionWrap, (JSC::JSGlobalObject * globalObject,
diff --git a/src/js/builtins/BundlerPlugin.ts b/src/js/builtins/BundlerPlugin.ts
index 7be030ee8..d2c88b667 100644
--- a/src/js/builtins/BundlerPlugin.ts
+++ b/src/js/builtins/BundlerPlugin.ts
@@ -162,6 +162,9 @@ export function runSetupFunction(this: BundlerPlugin, setup: Setup, config: Buil
     onResolve,
     onStart: notImplementedIssueFn(2771, "On-start callbacks"),
     resolve: notImplementedIssueFn(2771, "build.resolve()"),
+    module: () => {
+      throw new TypeError("module() is not supported in Bun.build() yet. Only via Bun.plugin() at runtime");
+    },
     // esbuild's options argument is different, we provide some interop
     initialOptions: {
       ...config,
diff --git a/src/js/out/WebCoreJSBuiltins.cpp b/src/js/out/WebCoreJSBuiltins.cpp
index a60dfc281..31246276b 100644
--- a/src/js/out/WebCoreJSBuiltins.cpp
+++ b/src/js/out/WebCoreJSBuiltins.cpp
@@ -30,9 +30,9 @@ const char* const s_bundlerPluginRunOnResolvePluginsCode = "(function (specifier
 const JSC::ConstructAbility s_bundlerPluginRunSetupFunctionCodeConstructAbility = JSC::ConstructAbility::CannotConstruct;
 const JSC::ConstructorKind s_bundlerPluginRunSetupFunctionCodeConstructorKind = JSC::ConstructorKind::None;
 const JSC::ImplementationVisibility s_bundlerPluginRunSetupFunctionCodeImplementationVisibility = JSC::ImplementationVisibility::Public;
-const int s_bundlerPluginRunSetupFunctionCodeLength = 4001;
+const int s_bundlerPluginRunSetupFunctionCodeLength = 4133;
 static const JSC::Intrinsic s_bundlerPluginRunSetupFunctionCodeIntrinsic = JSC::NoIntrinsic;
-const char* const s_bundlerPluginRunSetupFunctionCode = "(function (setup, config) {\"use strict\";\n  var onLoadPlugins = new Map, onResolvePlugins = new Map;\n  function validate(filterObject, callback, map) {\n    if (!filterObject || !@isObject(filterObject))\n      @throwTypeError('Expected an object with \"filter\" RegExp');\n    if (!callback || !@isCallable(callback))\n      @throwTypeError(\"callback must be a function\");\n    var { filter, namespace = \"file\" } = filterObject;\n    if (!filter)\n      @throwTypeError('Expected an object with \"filter\" RegExp');\n    if (!@isRegExpObject(filter))\n      @throwTypeError(\"filter must be a RegExp\");\n    if (namespace && typeof namespace !== \"string\")\n      @throwTypeError(\"namespace must be a string\");\n    if ((namespace\?.length \?\? 0) === 0)\n      namespace = \"file\";\n    if (!/^([/@a-zA-Z0-9_\\\\-]+)$/.test(namespace))\n      @throwTypeError(\"namespace can only contain $a-zA-Z0-9_\\\\-\");\n    var callbacks = map.@get(namespace);\n    if (!callbacks)\n      map.@set(namespace, [[filter, callback]]);\n    else\n      @arrayPush(callbacks, [filter, callback]);\n  }\n  function onLoad(filterObject, callback) {\n    validate(filterObject, callback, onLoadPlugins);\n  }\n  function onResolve(filterObject, callback) {\n    validate(filterObject, callback, onResolvePlugins);\n  }\n  const processSetupResult = () => {\n    var anyOnLoad = !1, anyOnResolve = !1;\n    for (var [namespace, callbacks] of onLoadPlugins.entries())\n      for (var [filter] of callbacks)\n        this.addFilter(filter, namespace, 1), anyOnLoad = !0;\n    for (var [namespace, callbacks] of onResolvePlugins.entries())\n      for (var [filter] of callbacks)\n        this.addFilter(filter, namespace, 0), anyOnResolve = !0;\n    if (anyOnResolve) {\n      var onResolveObject = this.onResolve;\n      if (!onResolveObject)\n        this.onResolve = onResolvePlugins;\n      else\n        for (var [namespace, callbacks] of onResolvePlugins.entries()) {\n          var existing = onResolveObject.@get(namespace);\n          if (!existing)\n            onResolveObject.@set(namespace, callbacks);\n          else\n            onResolveObject.@set(namespace, existing.concat(callbacks));\n        }\n    }\n    if (anyOnLoad) {\n      var onLoadObject = this.onLoad;\n      if (!onLoadObject)\n        this.onLoad = onLoadPlugins;\n      else\n        for (var [namespace, callbacks] of onLoadPlugins.entries()) {\n          var existing = onLoadObject.@get(namespace);\n          if (!existing)\n            onLoadObject.@set(namespace, callbacks);\n          else\n            onLoadObject.@set(namespace, existing.concat(callbacks));\n        }\n    }\n    return anyOnLoad || anyOnResolve;\n  };\n  var setupResult = setup({\n    config,\n    onDispose: () => @throwTypeError(\"@{@2} is not implemented yet. See https://github.com/oven-sh/bun/issues/@1\"),\n    onEnd: () => @throwTypeError(\"@{@2} is not implemented yet. See https://github.com/oven-sh/bun/issues/@1\"),\n    onLoad,\n    onResolve,\n    onStart: () => @throwTypeError(\"@{@2} is not implemented yet. See https://github.com/oven-sh/bun/issues/@1\"),\n    resolve: () => @throwTypeError(\"@{@2} is not implemented yet. See https://github.com/oven-sh/bun/issues/@1\"),\n    initialOptions: {\n      ...config,\n      bundle: !0,\n      entryPoints: config.entrypoints \?\? config.entryPoints \?\? [],\n      minify: typeof config.minify === \"boolean\" \? config.minify : !1,\n      minifyIdentifiers: config.minify === !0 || config.minify\?.identifiers,\n      minifyWhitespace: config.minify === !0 || config.minify\?.whitespace,\n      minifySyntax: config.minify === !0 || config.minify\?.syntax,\n      outbase: config.root,\n      platform: config.target === \"bun\" \? \"node\" : config.target\n    },\n    esbuild: {}\n  });\n  if (setupResult && @isPromise(setupResult))\n    if (@getPromiseInternalField(setupResult, @promiseFieldFlags) & @promiseStateFulfilled)\n      setupResult = @getPromiseInternalField(setupResult, @promiseFieldReactionsOrResult);\n    else\n      return setupResult.@then(processSetupResult);\n  return processSetupResult();\n})\n";
+const char* const s_bundlerPluginRunSetupFunctionCode = "(function (setup, config) {\"use strict\";\n  var onLoadPlugins = new Map, onResolvePlugins = new Map;\n  function validate(filterObject, callback, map) {\n    if (!filterObject || !@isObject(filterObject))\n      @throwTypeError('Expected an object with \"filter\" RegExp');\n    if (!callback || !@isCallable(callback))\n      @throwTypeError(\"callback must be a function\");\n    var { filter, namespace = \"file\" } = filterObject;\n    if (!filter)\n      @throwTypeError('Expected an object with \"filter\" RegExp');\n    if (!@isRegExpObject(filter))\n      @throwTypeError(\"filter must be a RegExp\");\n    if (namespace && typeof namespace !== \"string\")\n      @throwTypeError(\"namespace must be a string\");\n    if ((namespace\?.length \?\? 0) === 0)\n      namespace = \"file\";\n    if (!/^([/@a-zA-Z0-9_\\\\-]+)$/.test(namespace))\n      @throwTypeError(\"namespace can only contain $a-zA-Z0-9_\\\\-\");\n    var callbacks = map.@get(namespace);\n    if (!callbacks)\n      map.@set(namespace, [[filter, callback]]);\n    else\n      @arrayPush(callbacks, [filter, callback]);\n  }\n  function onLoad(filterObject, callback) {\n    validate(filterObject, callback, onLoadPlugins);\n  }\n  function onResolve(filterObject, callback) {\n    validate(filterObject, callback, onResolvePlugins);\n  }\n  const processSetupResult = () => {\n    var anyOnLoad = !1, anyOnResolve = !1;\n    for (var [namespace, callbacks] of onLoadPlugins.entries())\n      for (var [filter] of callbacks)\n        this.addFilter(filter, namespace, 1), anyOnLoad = !0;\n    for (var [namespace, callbacks] of onResolvePlugins.entries())\n      for (var [filter] of callbacks)\n        this.addFilter(filter, namespace, 0), anyOnResolve = !0;\n    if (anyOnResolve) {\n      var onResolveObject = this.onResolve;\n      if (!onResolveObject)\n        this.onResolve = onResolvePlugins;\n      else\n        for (var [namespace, callbacks] of onResolvePlugins.entries()) {\n          var existing = onResolveObject.@get(namespace);\n          if (!existing)\n            onResolveObject.@set(namespace, callbacks);\n          else\n            onResolveObject.@set(namespace, existing.concat(callbacks));\n        }\n    }\n    if (anyOnLoad) {\n      var onLoadObject = this.onLoad;\n      if (!onLoadObject)\n        this.onLoad = onLoadPlugins;\n      else\n        for (var [namespace, callbacks] of onLoadPlugins.entries()) {\n          var existing = onLoadObject.@get(namespace);\n          if (!existing)\n            onLoadObject.@set(namespace, callbacks);\n          else\n            onLoadObject.@set(namespace, existing.concat(callbacks));\n        }\n    }\n    return anyOnLoad || anyOnResolve;\n  };\n  var setupResult = setup({\n    config,\n    onDispose: () => @throwTypeError(\"@{@2} is not implemented yet. See https://github.com/oven-sh/bun/issues/@1\"),\n    onEnd: () => @throwTypeError(\"@{@2} is not implemented yet. See https://github.com/oven-sh/bun/issues/@1\"),\n    onLoad,\n    onResolve,\n    onStart: () => @throwTypeError(\"@{@2} is not implemented yet. See https://github.com/oven-sh/bun/issues/@1\"),\n    resolve: () => @throwTypeError(\"@{@2} is not implemented yet. See https://github.com/oven-sh/bun/issues/@1\"),\n    module: () => {\n      @throwTypeError(\"module() is not supported in Bun.build() yet. Only via Bun.plugin() at runtime\");\n    },\n    initialOptions: {\n      ...config,\n      bundle: !0,\n      entryPoints: config.entrypoints \?\? config.entryPoints \?\? [],\n      minify: typeof config.minify === \"boolean\" \? config.minify : !1,\n      minifyIdentifiers: config.minify === !0 || config.minify\?.identifiers,\n      minifyWhitespace: config.minify === !0 || config.minify\?.whitespace,\n      minifySyntax: config.minify === !0 || config.minify\?.syntax,\n      outbase: config.root,\n      platform: config.target === \"bun\" \? \"node\" : config.target\n    },\n    esbuild: {}\n  });\n  if (setupResult && @isPromise(setupResult))\n    if (@getPromiseInternalField(setupResult, @promiseFieldFlags) & @promiseStateFulfilled)\n      setupResult = @getPromiseInternalField(setupResult, @promiseFieldReactionsOrResult);\n    else\n      return setupResult.@then(processSetupResult);\n  return processSetupResult();\n})\n";
 
 #define DEFINE_BUILTIN_GENERATOR(codeName, functionName, overriddenName, argumentCount) \
 JSC::FunctionExecutable* codeName##Generator(JSC::VM& vm) \
diff --git a/test/bundler/bun-build-api.test.ts b/test/bundler/bun-build-api.test.ts
index 3c2308d94..d1f1a10b8 100644
--- a/test/bundler/bun-build-api.test.ts
+++ b/test/bundler/bun-build-api.test.ts
@@ -290,4 +290,27 @@ describe("Bun.build", () => {
     // depends on the ws package in the test/node_modules.
     expect(content).toContain("var websocket = __toESM(require_websocket(), 1);");
   });
+
+  test("module() throws error", async () => {
+    expect(() =>
+      Bun.build({
+        entrypoints: [join(import.meta.dir, "./fixtures/trivial/bundle-ws.ts")],
+        plugins: [
+          {
+            name: "test",
+            setup: b => {
+              b.module("ad", () => {
+                return {
+                  exports: {
+                    hello: "world",
+                  },
+                  loader: "object",
+                };
+              });
+            },
+          },
+        ],
+      }),
+    ).toThrow();
+  });
 });
diff --git a/test/js/bun/plugin/module-plugins.ts b/test/js/bun/plugin/module-plugins.ts
new file mode 100644
index 000000000..d6034c5df
--- /dev/null
+++ b/test/js/bun/plugin/module-plugins.ts
@@ -0,0 +1,38 @@
+import { plugin } from "bun";
+plugin({
+  name: "i am virtual!",
+  setup(builder) {
+    builder.module("my-virtual-module-async", async () => {
+      // check
+      await Bun.sleep(1);
+      return {
+        exports: {
+          hello: "world",
+        },
+        loader: "object",
+      };
+    });
+
+    builder.module("my-virtual-module-sync", () => {
+      return {
+        exports: {
+          hello: "world",
+        },
+        loader: "object",
+      };
+    });
+
+    builder.onLoad({ filter: /.*/, namespace: "rejected-promise" }, async ({ path }) => {
+      throw new Error("Rejected Promise");
+    });
+
+    builder.onResolve({ filter: /.*/, namespace: "rejected-promise2" }, ({ path }) => ({
+      namespace: "rejected-promise2",
+      path,
+    }));
+
+    builder.onLoad({ filter: /.*/, namespace: "rejected-promise2" }, ({ path }) => {
+      return Promise.reject(new Error("Rejected Promise"));
+    });
+  },
+});
diff --git a/test/js/bun/plugin/plugins.test.ts b/test/js/bun/plugin/plugins.test.ts
index c2827f600..2d3cfa1fa 100644
--- a/test/js/bun/plugin/plugins.test.ts
+++ b/test/js/bun/plugin/plugins.test.ts
@@ -185,6 +185,7 @@ plugin({
 
 // This is to test that it works when imported from a separate file
 import "../../third_party/svelte";
+import "./module-plugins";
 
 describe("require", () => {
   it("SSRs `<h1>Hello world!</h1>` with Svelte", () => {
@@ -210,6 +211,83 @@ describe("require", () => {
   });
 });
 
+describe("module", () => {
+  it("throws with require()", () => {
+    expect(() => require("my-virtual-module-async")).toThrow();
+  });
+
+  it("async module works with async import", async () => {
+    // @ts-expect-error
+    const { hello } = await import("my-virtual-module-async");
+
+    expect(hello).toBe("world");
+    delete require.cache["my-virtual-module-async"];
+  });
+
+  it("sync module module works with require()", async () => {
+    const { hello } = require("my-virtual-module-sync");
+
+    expect(hello).toBe("world");
+    delete require.cache["my-virtual-module-sync"];
+  });
+
+  it("sync module module works with require.resolve()", async () => {
+    expect(require.resolve("my-virtual-module-sync")).toBe("my-virtual-module-sync");
+    delete require.cache["my-virtual-module-sync"];
+  });
+
+  it("sync module module works with import", async () => {
+    // @ts-expect-error
+    const { hello } = await import("my-virtual-module-sync");
+
+    expect(hello).toBe("world");
+    delete require.cache["my-virtual-module-sync"];
+  });
+
+  it("modules are overridable", async () => {
+    // @ts-expect-error
+    let { hello, there } = await import("my-virtual-module-sync");
+    expect(there).toBeUndefined();
+    expect(hello).toBe("world");
+
+    Bun.plugin({
+      setup(builder) {
+        builder.module("my-virtual-module-sync", () => ({
+          exports: {
+            there: true,
+          },
+          loader: "object",
+        }));
+      },
+    });
+
+    {
+      const { there, hello } = require("my-virtual-module-sync");
+      expect(there).toBe(true);
+      expect(hello).toBeUndefined();
+    }
+
+    Bun.plugin({
+      setup(builder) {
+        builder.module("my-virtual-module-sync", () => ({
+          exports: {
+            yo: true,
+          },
+          loader: "object",
+        }));
+      },
+    });
+
+    {
+      // @ts-expect-error
+      const { there, hello, yo } = await import("my-virtual-module-sync");
+      expect(yo).toBe(true);
+      expect(hello).toBeUndefined();
+      expect(there).toBeUndefined();
+    }
+  });
+});
+
 describe("dynamic import", () => {
   it("SSRs `<h1>Hello world!</h1>` with Svelte", async () => {
     const { default: App }: any = await import("./hello.svelte");