diagnostics_channel: publish tracing:module.require and tracing:module.import

src/js/builtins/CommonJS.ts

@@ -7,9 +7,29 @@ export function main() {
 
 // This function is bound when constructing instances of CommonJSModule
 $visibility = "Private";
-export function require(this: JSCommonJSModule, _: string) {
-  // Do not use $tailCallForwardArguments here, it causes https://github.com/oven-sh/bun/issues/9225
-  return $overridableRequire.$apply(this, arguments);
+export function require(this: JSCommonJSModule, id: string) {
+  const ch = require("internal/module_tracing").requireChannel;
+  if (!ch.hasSubscribers) {
+    // Do not use $tailCallForwardArguments here, it causes https://github.com/oven-sh/bun/issues/9225
+    return $overridableRequire.$apply(this, arguments);
+  }
+  const context = { __proto__: null, id, parentFilename: this && this.filename };
+  const self = this;
+  const args = arguments;
+  const { start, end, error } = ch;
+  return start.runStores(context, () => {
+    try {
+      const result = $overridableRequire.$apply(self, args);
+      context.result = result;
+      return result;
+    } catch (err) {
+      context.error = err;
+      error.publish(context);
+      throw err;
+    } finally {
+      end.publish(context);
+    }
+  });
 }
 
 // overridableRequire can be overridden by setting `Module.prototype.require`

src/js/internal/module_tracing.ts

@@ -0,0 +1,15 @@
+// node:diagnostics_channel TracingChannels for module loading.
+// https://nodejs.org/api/diagnostics_channel.html#built-in-channels
+const { tracingChannel } = require("node:diagnostics_channel");
+
+const requireChannel = tracingChannel("module.require");
+const importChannel = tracingChannel("module.import");
+
+// Called from C++ GlobalObject::moduleLoaderImportModule to wrap a dynamic
+// import() once a "tracing:module.*" subscriber exists.
+function traceDynamicImport(promise, url, parentURL) {
+  if (!importChannel.hasSubscribers) return promise;
+  return importChannel.tracePromise(() => promise, { __proto__: null, parentURL, url });
+}
+
+export default { requireChannel, importChannel, traceDynamicImport };

src/js/node/diagnostics_channel.ts

@@ -58,10 +58,16 @@
   }
 }
 
+let enableModuleTracing: (() => void) | undefined;
+
 function markActive(channel) {
   ObjectSetPrototypeOf.$call(null, channel, ActiveChannel.prototype);
   channel._subscribers = [];
   channel._stores = new SafeMap();
+  // Notify the native dynamic-import hook that it now needs to publish.
+  if (typeof channel.name === "string" && channel.name.startsWith("tracing:module.")) {
+    (enableModuleTracing ??= $newCppFunction("NodeDiagnosticsChannel.cpp", "jsEnableModuleTracingSubscribers", 0))();
+  }
 }
 
 function maybeMarkInactive(channel) {
@@ -281,6 +287,16 @@
     }
   }
 
+  get hasSubscribers() {
+    return (
+      this.start.hasSubscribers ||
+      this.end.hasSubscribers ||
+      this.asyncStart.hasSubscribers ||
+      this.asyncEnd.hasSubscribers ||
+      this.error.hasSubscribers
+    );
+  }
+
   subscribe(handlers) {
     for (const name of traceEvents) {
       if (!handlers[name]) continue;

src/jsc/bindings/NodeDiagnosticsChannel.cpp

@@ -0,0 +1,19 @@
+#include "config.h"
+
+#include "ZigGlobalObject.h"
+
+namespace Bun {
+
+using namespace JSC;
+
+// Called from node:diagnostics_channel when a subscriber is first added to any
+// "tracing:module.*" channel. Flips a one-way de-opt flag so the native
+// dynamic-import hook starts routing through the JS tracer.
+JSC_DEFINE_HOST_FUNCTION(jsEnableModuleTracingSubscribers, (JSC::JSGlobalObject * globalObject, JSC::CallFrame*))
+{
+    auto* global = uncheckedDowncast<Zig::GlobalObject>(globalObject);
+    global->hasModuleTracingSubscribers = true;
+    return JSC::JSValue::encode(JSC::jsUndefined());
+}
+
+}

src/jsc/bindings/NodeDiagnosticsChannel.h

@@ -0,0 +1,9 @@
+#include "config.h"
+#include "ZigGlobalObject.h"
+#include <wtf/PlatformCallingConventions.h>
+
+namespace Bun {
+
+JSC_DECLARE_HOST_FUNCTION(jsEnableModuleTracingSubscribers);
+
+}

src/jsc/bindings/ZigGlobalObject.cpp

@@ -2275,6 +2275,18 @@ void GlobalObject::finishCreation(VM& vm)
             init.set(JSC::JSFunction::create(init.vm, init.owner, wasmStreamingConsumeStreamCodeGenerator(init.vm), init.owner));
         });
 
+    m_traceDynamicImportFunction.initLater(
+        [](const Initializer<JSFunction>& init) {
+            auto scope = DECLARE_THROW_SCOPE(init.vm);
+            JSValue mod = uncheckedDowncast<Zig::GlobalObject>(init.owner)->internalModuleRegistry()->requireId(init.owner, init.vm, Bun::InternalModuleRegistry::Field::InternalModuleTracing);
+            RETURN_IF_EXCEPTION(scope, );
+            RELEASE_ASSERT(mod.isObject());
+            auto prop = mod.getObject()->getIfPropertyExists(init.owner, Identifier::fromString(init.vm, "traceDynamicImport"_s));
+            RETURN_IF_EXCEPTION(scope, );
+            ASSERT(prop);
+            init.set(uncheckedDowncast<JSFunction>(prop));
+        });
+
     m_nativeMicrotaskTrampoline.initLater(
         [](const Initializer<JSFunction>& init) {
             init.set(JSFunction::create(init.vm, init.owner, 2, ""_s, functionNativeMicrotaskTrampoline, ImplementationVisibility::Private));
@@ -3511,6 +3523,39 @@ JSC::Identifier GlobalObject::moduleLoaderResolve(JSGlobalObject* jsGlobalObject
     }
 }
 
+static JSC::JSPromise* traceDynamicImport(Zig::GlobalObject* globalObject, JSC::JSPromise* promise, JSC::JSString* moduleNameValue, const SourceOrigin& sourceOrigin)
+{
+    if (!promise) [[unlikely]]
+        return promise;
+
+    VM& vm = JSC::getVM(globalObject);
+    auto scope = DECLARE_THROW_SCOPE(vm);
+
+    auto* tracer = globalObject->traceDynamicImportFunction();
+    if (scope.exception()) [[unlikely]] {
+        return JSC::JSPromise::rejectedPromiseWithCaughtException(globalObject, scope);
+    }
+    if (!tracer) [[unlikely]]
+        return promise;
+
+    JSC::MarkedArgumentBuffer args;
+    args.append(promise);
+    args.append(moduleNameValue);
+    auto& sourceURL = sourceOrigin.url();
+    args.append(sourceURL.isEmpty() ? JSC::jsUndefined() : JSC::jsString(vm, sourceURL.string()));
+    ASSERT(!args.hasOverflowed());
+
+    auto callData = JSC::getCallData(tracer);
+    auto result = JSC::profiledCall(globalObject, JSC::ProfilingReason::API, tracer, callData, JSC::jsUndefined(), args);
+    if (scope.exception()) [[unlikely]] {
+        return JSC::JSPromise::rejectedPromiseWithCaughtException(globalObject, scope);
+    }
+
+    if (result.inherits<JSC::JSPromise>())
+        return static_cast<JSC::JSPromise*>(result.asCell());
+    return promise;
+}
+
 JSC::JSPromise* GlobalObject::moduleLoaderImportModule(JSGlobalObject* jsGlobalObject,
     JSModuleLoader*,
     JSString* moduleNameValue,
@@ -3524,6 +3569,8 @@ JSC::JSPromise* GlobalObject::moduleLoaderImportModule(JSGlobalObject* jsGlobalO
     VM& vm = JSC::getVM(globalObject);
     auto scope = DECLARE_THROW_SCOPE(vm);
 
+    const bool needsTracing = globalObject->hasModuleTracingSubscribers;
+
     {
         JSC::JSPromise* result = NodeVM::importModule(globalObject, moduleNameValue, parameters, sourceOrigin);
         RETURN_IF_EXCEPTION(scope, nullptr);
@@ -3562,7 +3609,10 @@ JSC::JSPromise* GlobalObject::moduleLoaderImportModule(JSGlobalObject* jsGlobalO
 
             auto result = JSC::importModule(globalObject, resolvedIdentifier, JSC::Identifier(), parameters, nullptr, /* deferred */ false, referrerAsyncOrder);
             if (scope.exception()) [[unlikely]] {
-                return JSC::JSPromise::rejectedPromiseWithCaughtException(globalObject, scope);
+                result = JSC::JSPromise::rejectedPromiseWithCaughtException(globalObject, scope);
+            }
+            if (needsTracing) [[unlikely]] {
+                RELEASE_AND_RETURN(scope, traceDynamicImport(globalObject, result, moduleNameValue, sourceOrigin));
             }
             return result;
         }
@@ -3601,7 +3651,11 @@ JSC::JSPromise* GlobalObject::moduleLoaderImportModule(JSGlobalObject* jsGlobalO
             moduleNameZ.deref();
             sourceOriginZ.deref();
 
-            return JSC::JSPromise::rejectedPromiseWithCaughtException(globalObject, scope);
+            auto* rejected = JSC::JSPromise::rejectedPromiseWithCaughtException(globalObject, scope);
+            if (needsTracing) [[unlikely]] {
+                RELEASE_AND_RETURN(scope, traceDynamicImport(globalObject, rejected, moduleNameValue, sourceOrigin));
+            }
+            return rejected;
         }
 
         if (queryString.isEmpty()) {
@@ -3622,7 +3676,11 @@ JSC::JSPromise* GlobalObject::moduleLoaderImportModule(JSGlobalObject* jsGlobalO
     auto result = JSC::importModule(globalObject, resolvedIdentifier,
         JSC::Identifier(), WTF::move(parameters), nullptr, /* deferred */ false, referrerAsyncOrder);
     if (scope.exception()) [[unlikely]] {
-        return JSC::JSPromise::rejectedPromiseWithCaughtException(globalObject, scope);
+        result = JSC::JSPromise::rejectedPromiseWithCaughtException(globalObject, scope);
+    }
+
+    if (needsTracing) [[unlikely]] {
+        RELEASE_AND_RETURN(scope, traceDynamicImport(globalObject, result, moduleNameValue, sourceOrigin));
     }
 
     ASSERT(result);

src/jsc/bindings/ZigGlobalObject.h

@@ -291,6 +291,7 @@ class GlobalObject : public Bun::GlobalScope {
     JSC::JSFunction* utilInspectStylizeNoColorFunction() const { return m_utilInspectStylizeNoColorFunction.getInitializedOnMainThread(this); }
 
     JSC::JSFunction* wasmStreamingConsumeStreamFunction() const { return m_wasmStreamingConsumeStreamFunction.getInitializedOnMainThread(this); }
+    JSC::JSFunction* traceDynamicImportFunction() const { return m_traceDynamicImportFunction.getInitializedOnMainThread(this); }
 
     JSObject* requireFunctionUnbound() const { return m_requireFunctionUnbound.getInitializedOnMainThread(this); }
     JSObject* requireResolveFunctionUnbound() const { return m_requireResolveFunctionUnbound.getInitializedOnMainThread(this); }
@@ -597,6 +598,7 @@ class GlobalObject : public Bun::GlobalScope {
     V(private, LazyPropertyOfGlobalObject<JSFunction>, m_utilInspectStylizeColorFunction)                    \
     V(private, LazyPropertyOfGlobalObject<JSFunction>, m_utilInspectStylizeNoColorFunction)                  \
     V(private, LazyPropertyOfGlobalObject<JSFunction>, m_wasmStreamingConsumeStreamFunction)                 \
+    V(private, LazyPropertyOfGlobalObject<JSFunction>, m_traceDynamicImportFunction)                         \
     V(private, LazyPropertyOfGlobalObject<WebCore::JSStreamsRuntime>, m_streamsRuntime)                      \
     V(private, LazyPropertyOfGlobalObject<JSMap>, m_requireMap)                                              \
     V(private, LazyPropertyOfGlobalObject<JSObject>, m_JSArrayBufferControllerPrototype)                     \
@@ -768,6 +770,8 @@ class GlobalObject : public Bun::GlobalScope {
     bool hasOverriddenModuleWrapper = false;
     // De-optimization once `require("module").runMain` is written to
     bool hasOverriddenModuleRunMain = false;
+    // De-optimization once a diagnostics_channel "tracing:module.*" subscriber is added
+    bool hasModuleTracingSubscribers = false;
 
     // WeakGCMap<uint64_t, JSObject> — JS-level dedup of SecureContext by
     // config digest. WeakGCMap self-registers with the heap, so no