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domain: support promises · nodejs/node@84dabe8 · GitHub

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domain: support promises
Fixes: #10724 PR-URL: #12489 Reviewed-By: Matthew Loring <mattloring@google.com> Reviewed-By: Julien Gilli <jgilli@nodejs.org> Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
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‎doc/api/domain.md‎

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# Domain
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<!-- YAML
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changes:
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- version: REPLACEME
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pr-url: https://github.com/nodejs/node/pull/12489
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description: Handlers for `Promise`s are now invoked in the domain in which
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the first promise of a chain was created.
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-->
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> Stability: 0 - Deprecated
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@@ -444,6 +451,49 @@ d.run(() => {
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In this example, the `d.on('error')` handler will be triggered, rather
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than crashing the program.
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## Domains and Promises
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As of Node REPLACEME, the handlers of Promises are run inside the domain in
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which the call to `.then` or `.catch` itself was made:
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```js
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const d1 = domain.create();
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const d2 = domain.create();
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let p;
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d1.run(() => {
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p = Promise.resolve(42);
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});
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d2.run(() => {
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p.then((v) => {
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// running in d2
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});
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});
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```
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A callback may be bound to a specific domain using [`domain.bind(callback)`][]:
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```js
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const d1 = domain.create();
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const d2 = domain.create();
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let p;
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d1.run(() => {
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p = Promise.resolve(42);
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});
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d2.run(() => {
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p.then(p.domain.bind((v) => {
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// running in d1
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}));
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});
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```
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Note that domains will not interfere with the error handling mechanisms for
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Promises, i.e. no `error` event will be emitted for unhandled Promise
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rejections.
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[`domain.add(emitter)`]: #domain_domain_add_emitter
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[`domain.bind(callback)`]: #domain_domain_bind_callback
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[`domain.dispose()`]: #domain_domain_dispose

‎src/node.cc‎

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@@ -143,6 +143,7 @@ using v8::Number;
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using v8::Object;
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using v8::ObjectTemplate;
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using v8::Promise;
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using v8::PromiseHookType;
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using v8::PromiseRejectMessage;
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using v8::PropertyCallbackInfo;
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using v8::ScriptOrigin;
@@ -1114,6 +1115,58 @@ bool ShouldAbortOnUncaughtException(Isolate* isolate) {
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}
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void DomainPromiseHook(PromiseHookType type,
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Local<Promise> promise,
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Local<Value> parent,
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void* arg) {
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Environment* env = static_cast<Environment*>(arg);
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Local<Context> context = env->context();
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if (type == PromiseHookType::kResolve) return;
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if (type == PromiseHookType::kInit && env->in_domain()) {
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promise->Set(context,
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env->domain_string(),
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env->domain_array()->Get(context,
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0).ToLocalChecked()).FromJust();
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return;
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}
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// Loosely based on node::MakeCallback().
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Local<Value> domain_v =
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promise->Get(context, env->domain_string()).ToLocalChecked();
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if (!domain_v->IsObject())
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return;
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Local<Object> domain = domain_v.As<Object>();
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if (domain->Get(context, env->disposed_string())
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.ToLocalChecked()->IsTrue()) {
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return;
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}
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if (type == PromiseHookType::kBefore) {
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Local<Value> enter_v =
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domain->Get(context, env->enter_string()).ToLocalChecked();
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if (enter_v->IsFunction()) {
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if (enter_v.As<Function>()->Call(context, domain, 0, nullptr).IsEmpty()) {
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FatalError("node::PromiseHook",
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"domain enter callback threw, please report this "
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"as a bug in Node.js");
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}
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}
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} else {
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Local<Value> exit_v =
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domain->Get(context, env->exit_string()).ToLocalChecked();
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if (exit_v->IsFunction()) {
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if (exit_v.As<Function>()->Call(context, domain, 0, nullptr).IsEmpty()) {
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FatalError("node::MakeCallback",
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"domain exit callback threw, please report this "
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"as a bug in Node.js");
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}
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}
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}
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}
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void SetupDomainUse(const FunctionCallbackInfo<Value>& args) {
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Environment* env = Environment::GetCurrent(args);
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Local<ArrayBuffer> array_buffer =
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ArrayBuffer::New(env->isolate(), fields, sizeof(*fields) * fields_count);
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env->AddPromiseHook(DomainPromiseHook, static_cast<void*>(env));
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args.GetReturnValue().Set(Uint32Array::New(array_buffer, 0, fields_count));
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}
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void RunMicrotasks(const FunctionCallbackInfo<Value>& args) {
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args.GetIsolate()->RunMicrotasks();
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}

‎test/parallel/test-domain-promise.js‎

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'use strict';
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const common = require('../common');
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const assert = require('assert');
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const domain = require('domain');
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const fs = require('fs');
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const vm = require('vm');
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common.crashOnUnhandledRejection();
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{
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const d = domain.create();
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d.run(common.mustCall(() => {
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Promise.resolve().then(common.mustCall(() => {
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assert.strictEqual(process.domain, d);
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}));
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}));
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}
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{
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const d = domain.create();
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d.run(common.mustCall(() => {
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Promise.resolve().then(() => {}).then(() => {}).then(common.mustCall(() => {
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assert.strictEqual(process.domain, d);
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}));
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}));
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}
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{
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const d = domain.create();
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d.run(common.mustCall(() => {
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vm.runInNewContext(`Promise.resolve().then(common.mustCall(() => {
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assert.strictEqual(process.domain, d);
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}));`, { common, assert, process, d });
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}));
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}
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{
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const d1 = domain.create();
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const d2 = domain.create();
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let p;
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d1.run(common.mustCall(() => {
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p = Promise.resolve(42);
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}));
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d2.run(common.mustCall(() => {
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p.then(common.mustCall((v) => {
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assert.strictEqual(process.domain, d2);
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assert.strictEqual(p.domain, d1);
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}));
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}));
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}
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{
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const d1 = domain.create();
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const d2 = domain.create();
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let p;
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d1.run(common.mustCall(() => {
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p = Promise.resolve(42);
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}));
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d2.run(common.mustCall(() => {
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p.then(p.domain.bind(common.mustCall((v) => {
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assert.strictEqual(process.domain, d1);
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assert.strictEqual(p.domain, d1);
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})));
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}));
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}
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{
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const d1 = domain.create();
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const d2 = domain.create();
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let p;
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d1.run(common.mustCall(() => {
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p = Promise.resolve(42);
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}));
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d1.run(common.mustCall(() => {
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d2.run(common.mustCall(() => {
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p.then(common.mustCall((v) => {
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assert.strictEqual(process.domain, d2);
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assert.strictEqual(p.domain, d1);
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}));
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}));
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}));
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}
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{
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const d1 = domain.create();
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const d2 = domain.create();
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let p;
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d1.run(common.mustCall(() => {
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p = Promise.reject(new Error('foobar'));
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}));
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d2.run(common.mustCall(() => {
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p.catch(common.mustCall((v) => {
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assert.strictEqual(process.domain, d2);
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assert.strictEqual(p.domain, d1);
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}));
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}));
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}
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{
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const d = domain.create();
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d.run(common.mustCall(() => {
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Promise.resolve().then(common.mustCall(() => {
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setTimeout(common.mustCall(() => {
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assert.strictEqual(process.domain, d);
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}), 0);
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}));
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}));
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}
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{
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const d = domain.create();
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d.run(common.mustCall(() => {
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Promise.resolve().then(common.mustCall(() => {
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fs.readFile(__filename, common.mustCall(() => {
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assert.strictEqual(process.domain, d);
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}));
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}));
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}));
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}

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