domain: remove native domain code

With the async_hooks callback trampoline, domains no longer need any
native code. With this, domains can exist in pure JavaScript.

PR-URL: #33801
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Vladimir de Turckheim <[email protected]>
Reviewed-By: Gus Caplan <[email protected]>
Reviewed-By: Andrey Pechkurov <[email protected]>
Reviewed-By: Gerhard Stöbich <[email protected]>

Author: Qard

lib/domain.js

@@ -42,6 +42,7 @@ const {
   ERR_UNHANDLED_ERROR
 } = require('internal/errors').codes;
 const { createHook } = require('async_hooks');
+const { useDomainTrampoline } = require('internal/async_hooks');
 
 // TODO(addaleax): Use a non-internal solution for this.
 const kWeak = Symbol('kWeak');
@@ -145,7 +146,7 @@ function topLevelDomainCallback(cb, ...args) {
 // another one. The stack is each entered domain.
 let stack = [];
 exports._stack = stack;
-internalBinding('domain').enable(topLevelDomainCallback);
+useDomainTrampoline(topLevelDomainCallback);
 
 function updateExceptionCapture() {
   if (stack.every((domain) => domain.listenerCount('error') === 0)) {

lib/internal/async_hooks.js

@@ -106,8 +106,13 @@ const emitDestroyNative = emitHookFactory(destroy_symbol, 'emitDestroyNative');
 const emitPromiseResolveNative =
     emitHookFactory(promise_resolve_symbol, 'emitPromiseResolveNative');
 
-function callbackTrampoline(asyncId, cb, domain_cb, ...args) {
-  if (hasHooks(kBefore))
+let domain_cb;
+function useDomainTrampoline(fn) {
+  domain_cb = fn;
+}
+
+function callbackTrampoline(asyncId, cb, ...args) {
+  if (asyncId && hasHooks(kBefore))
     emitBeforeNative(asyncId);
 
   let result;
@@ -118,7 +123,7 @@ function callbackTrampoline(asyncId, cb, domain_cb, ...args) {
     result = ReflectApply(cb, this, args);
   }
 
-  if (hasHooks(kAfter))
+  if (asyncId && hasHooks(kAfter))
     emitAfterNative(asyncId);
 
   return result;
@@ -564,6 +569,7 @@ module.exports = {
   emitAfter: emitAfterScript,
   emitDestroy: emitDestroyScript,
   registerDestroyHook,
+  useDomainTrampoline,
   nativeHooks: {
     init: emitInitNative,
     before: emitBeforeNative,

node.gyp

@@ -590,7 +590,6 @@
         'src/node_contextify.cc',
         'src/node_credentials.cc',
         'src/node_dir.cc',
-        'src/node_domain.cc',
         'src/node_env_var.cc',
         'src/node_errors.cc',
         'src/node_file.cc',

src/api/callback.cc

@@ -173,29 +173,16 @@ MaybeLocal<Value> InternalMakeCallback(Environment* env,
     return MaybeLocal<Value>();
   }
 
-  Local<Function> domain_cb = env->domain_callback();
   MaybeLocal<Value> ret;
 
-  if (asyncContext.async_id != 0 && hook_count != 0) {
-    MaybeStackBuffer<Local<Value>, 16> args(3 + argc);
+  if (hook_count != 0) {
+    MaybeStackBuffer<Local<Value>, 16> args(2 + argc);
     args[0] = v8::Number::New(env->isolate(), asyncContext.async_id);
     args[1] = callback;
-    if (domain_cb.IsEmpty()) {
-      args[2] = Undefined(env->isolate());
-    } else {
-      args[2] = domain_cb;
-    }
     for (int i = 0; i < argc; i++) {
-      args[i + 3] = argv[i];
+      args[i + 2] = argv[i];
     }
     ret = hook_cb->Call(env->context(), recv, args.length(), &args[0]);
-  } else if (asyncContext.async_id == 0 && !domain_cb.IsEmpty()) {
-    MaybeStackBuffer<Local<Value>, 16> args(1 + argc);
-    args[0] = callback;
-    for (int i = 0; i < argc; i++) {
-      args[i + 1] = argv[i];
-    }
-    ret = domain_cb->Call(env->context(), recv, args.length(), &args[0]);
   } else {
     ret = callback->Call(env->context(), recv, argc, argv);
   }

src/env.h

@@ -486,7 +486,6 @@ constexpr size_t kFsStatsBufferLength =
   V(async_hooks_promise_resolve_function, v8::Function)                        \
   V(buffer_prototype_object, v8::Object)                                       \
   V(crypto_key_object_constructor, v8::Function)                               \
-  V(domain_callback, v8::Function)                                             \
   V(domexception_function, v8::Function)                                       \
   V(enhance_fatal_stack_after_inspector, v8::Function)                         \
   V(enhance_fatal_stack_before_inspector, v8::Function)                        \

src/node_binding.cc

@@ -48,7 +48,6 @@
   V(config)                                                                    \
   V(contextify)                                                                \
   V(credentials)                                                               \
-  V(domain)                                                                    \
   V(errors)                                                                    \
   V(fs)                                                                        \
   V(fs_dir)                                                                    \