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promises: refactor rejection handling #18207

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promises: refactor rejection handling #18207

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33 changes: 4 additions & 29 deletions lib/internal/process/next_tick.js
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ function setupNextTick() {
const async_hooks = require('internal/async_hooks');
const promises = require('internal/process/promises');
const errors = require('internal/errors');
const emitPendingUnhandledRejections = promises.setup(scheduleMicrotasks);
const { emitPromiseRejectionWarnings } = promises;
const getDefaultTriggerAsyncId = async_hooks.getDefaultTriggerAsyncId;
// Two arrays that share state between C++ and JS.
const { async_hook_fields, async_id_fields } = async_wrap;
Expand All @@ -30,6 +30,7 @@ function setupNextTick() {

// *Must* match Environment::TickInfo::Fields in src/env.h.
const kHasScheduled = 0;
const kHasPromiseRejections = 1;

const nextTickQueue = {
head: null,
Expand Down Expand Up @@ -58,39 +59,13 @@ function setupNextTick() {
}
};

var microtasksScheduled = false;

process.nextTick = nextTick;
// Needs to be accessible from beyond this scope.
process._tickCallback = _tickCallback;

// Set the nextTick() function for internal usage.
exports.nextTick = internalNextTick;

const microTasksTickObject = {
callback: runMicrotasksCallback,
args: undefined,
[async_id_symbol]: 0,
[trigger_async_id_symbol]: 0
};
function scheduleMicrotasks() {
if (microtasksScheduled)
return;

// For the moment all microtasks come from the void until the PromiseHook
// API is implemented.
nextTickQueue.push(microTasksTickObject);
microtasksScheduled = true;
}

function runMicrotasksCallback() {
microtasksScheduled = false;
runMicrotasks();

if (nextTickQueue.head !== null || emitPendingUnhandledRejections())
scheduleMicrotasks();
}

function _tickCallback() {
let tock;
do {
Expand Down Expand Up @@ -118,8 +93,8 @@ function setupNextTick() {
emitAfter(asyncId);
}
runMicrotasks();
emitPendingUnhandledRejections();
} while (nextTickQueue.head !== null);
} while (nextTickQueue.head !== null || emitPromiseRejectionWarnings());
tickInfo[kHasPromiseRejections] = 0;
}

class TickObject {
Expand Down
186 changes: 86 additions & 100 deletions lib/internal/process/promises.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,123 +2,109 @@

const { safeToString } = process.binding('util');

const promiseRejectEvent = process._promiseRejectEvent;
const hasBeenNotifiedProperty = new WeakMap();
const promiseToGuidProperty = new WeakMap();
const maybeUnhandledPromises = new WeakMap();
const pendingUnhandledRejections = [];
let lastPromiseId = 1;
const asyncHandledRejections = [];
let lastPromiseId = 0;

exports.setup = setupPromises;
module.exports = {
emitPromiseRejectionWarnings
};

function getAsynchronousRejectionWarningObject(uid) {
return new Error('Promise rejection was handled ' +
`asynchronously (rejection id: ${uid})`);
}

function setupPromises(scheduleMicrotasks) {
let deprecationWarned = false;
process._setupPromises(unhandledRejection, handledRejection);

process._setupPromises(function(event, promise, reason) {
if (event === promiseRejectEvent.unhandled)
unhandledRejection(promise, reason);
else if (event === promiseRejectEvent.handled)
rejectionHandled(promise);
else
require('assert').fail(null, null, 'unexpected PromiseRejectEvent');
function unhandledRejection(promise, reason) {
maybeUnhandledPromises.set(promise, {
reason,
uid: ++lastPromiseId,
warned: false
});
pendingUnhandledRejections.push(promise);
return true;
}

function unhandledRejection(promise, reason) {
hasBeenNotifiedProperty.set(promise, false);
promiseToGuidProperty.set(promise, lastPromiseId++);
addPendingUnhandledRejection(promise, reason);
function handledRejection(promise) {
const promiseInfo = maybeUnhandledPromises.get(promise);
if (promiseInfo !== undefined) {
maybeUnhandledPromises.delete(promise);
if (promiseInfo.warned) {
const { uid } = promiseInfo;
// Generate the warning object early to get a good stack trace.
const warning = new Error('Promise rejection was handled ' +
`asynchronously (rejection id: ${uid})`);
warning.name = 'PromiseRejectionHandledWarning';
warning.id = uid;
asyncHandledRejections.push({ promise, warning });
return true;
}
}
return false;
}

function rejectionHandled(promise) {
const hasBeenNotified = hasBeenNotifiedProperty.get(promise);
if (hasBeenNotified !== undefined) {
hasBeenNotifiedProperty.delete(promise);
const uid = promiseToGuidProperty.get(promise);
promiseToGuidProperty.delete(promise);
if (hasBeenNotified === true) {
let warning = null;
if (!process.listenerCount('rejectionHandled')) {
// Generate the warning object early to get a good stack trace.
warning = getAsynchronousRejectionWarningObject(uid);
}
process.nextTick(function() {
if (!process.emit('rejectionHandled', promise)) {
if (warning === null)
warning = getAsynchronousRejectionWarningObject(uid);
warning.name = 'PromiseRejectionHandledWarning';
warning.id = uid;
process.emitWarning(warning);
}
});
}

const unhandledRejectionErrName = 'UnhandledPromiseRejectionWarning';
function emitWarning(uid, reason) {
try {
if (reason instanceof Error) {
process.emitWarning(reason.stack, unhandledRejectionErrName);
} else {
process.emitWarning(safeToString(reason), unhandledRejectionErrName);
}
} catch (e) {
// ignored
}

function emitWarning(uid, reason) {
try {
if (reason instanceof Error) {
process.emitWarning(reason.stack, 'UnhandledPromiseRejectionWarning');
} else {
process.emitWarning(
safeToString(reason), 'UnhandledPromiseRejectionWarning'
);
}
} catch (e) {
// ignored
const warning = new Error(
'Unhandled promise rejection. This error originated either by ' +
'throwing inside of an async function without a catch block, ' +
'or by rejecting a promise which was not handled with .catch(). ' +
`(rejection id: ${uid})`
);
warning.name = unhandledRejectionErrName;
try {
if (reason instanceof Error) {
warning.stack = reason.stack;
}
} catch (err) {
// ignored
}
process.emitWarning(warning);
emitDeprecationWarning();
}

const warning = new Error(
'Unhandled promise rejection. This error originated either by ' +
'throwing inside of an async function without a catch block, ' +
'or by rejecting a promise which was not handled with .catch(). ' +
`(rejection id: ${uid})`
);
warning.name = 'UnhandledPromiseRejectionWarning';
try {
if (reason instanceof Error) {
warning.stack = reason.stack;
}
} catch (err) {
// ignored
}
process.emitWarning(warning);
if (!deprecationWarned) {
deprecationWarned = true;
process.emitWarning(
'Unhandled promise rejections are deprecated. In the future, ' +
'promise rejections that are not handled will terminate the ' +
'Node.js process with a non-zero exit code.',
'DeprecationWarning', 'DEP0018');
}
let deprecationWarned = false;
function emitDeprecationWarning() {
if (!deprecationWarned) {
deprecationWarned = true;
process.emitWarning(
'Unhandled promise rejections are deprecated. In the future, ' +
'promise rejections that are not handled will terminate the ' +
'Node.js process with a non-zero exit code.',
'DeprecationWarning', 'DEP0018');
}
}

function emitPendingUnhandledRejections() {
let hadListeners = false;
while (pendingUnhandledRejections.length > 0) {
const promise = pendingUnhandledRejections.shift();
const reason = pendingUnhandledRejections.shift();
if (hasBeenNotifiedProperty.get(promise) === false) {
hasBeenNotifiedProperty.set(promise, true);
const uid = promiseToGuidProperty.get(promise);
if (!process.emit('unhandledRejection', reason, promise)) {
emitWarning(uid, reason);
} else {
hadListeners = true;
}
}
function emitPromiseRejectionWarnings() {
while (asyncHandledRejections.length > 0) {
const { promise, warning } = asyncHandledRejections.shift();
if (!process.emit('rejectionHandled', promise)) {
process.emitWarning(warning);
}
return hadListeners;
}

function addPendingUnhandledRejection(promise, reason) {
pendingUnhandledRejections.push(promise, reason);
scheduleMicrotasks();
let hadListeners = false;
let len = pendingUnhandledRejections.length;
while (len--) {
const promise = pendingUnhandledRejections.shift();
const promiseInfo = maybeUnhandledPromises.get(promise);
if (promiseInfo !== undefined) {
promiseInfo.warned = true;
const { reason, uid } = promiseInfo;
if (!process.emit('unhandledRejection', reason, promise)) {
emitWarning(uid, reason);
} else {
hadListeners = true;
}
}
}

return emitPendingUnhandledRejections;
return hadListeners || pendingUnhandledRejections.length !== 0;
}
8 changes: 8 additions & 0 deletions src/env-inl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -264,6 +264,14 @@ inline bool Environment::TickInfo::has_scheduled() const {
return fields_[kHasScheduled] == 1;
}

inline bool Environment::TickInfo::has_promise_rejections() const {
return fields_[kHasPromiseRejections] == 1;
}

inline void Environment::TickInfo::promise_rejections_toggle_on() {
fields_[kHasPromiseRejections] = 1;
}

inline void Environment::AssignToContext(v8::Local<v8::Context> context,
const ContextInfo& info) {
context->SetAlignedPointerInEmbedderData(kContextEmbedderDataIndex, this);
Expand Down
7 changes: 6 additions & 1 deletion src/env.h
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Original file line number Diff line number Diff line change
Expand Up @@ -293,7 +293,8 @@ class ModuleWrap;
V(performance_entry_callback, v8::Function) \
V(performance_entry_template, v8::Function) \
V(process_object, v8::Object) \
V(promise_reject_function, v8::Function) \
V(promise_reject_handled_function, v8::Function) \
V(promise_reject_unhandled_function, v8::Function) \
V(promise_wrap_template, v8::ObjectTemplate) \
V(push_values_to_array_function, v8::Function) \
V(randombytes_constructor_template, v8::ObjectTemplate) \
Expand Down Expand Up @@ -482,13 +483,17 @@ class Environment {
public:
inline AliasedBuffer<uint8_t, v8::Uint8Array>& fields();
inline bool has_scheduled() const;
inline bool has_promise_rejections() const;

inline void promise_rejections_toggle_on();

private:
friend class Environment; // So we can call the constructor.
inline explicit TickInfo(v8::Isolate* isolate);

enum Fields {
kHasScheduled,
kHasPromiseRejections,
kFieldsCount
};

Expand Down
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