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Promises/better unhandled rejection message #17158

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Promises/better unhandled rejection message #17158

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a29fe91
Improved unhandled rejection message
MadaraUchiha Nov 20, 2017
ba4adc5
Make tests pass
MadaraUchiha Nov 20, 2017
ab45e60
Wrap reason with unsafeToString() if it's a string
MadaraUchiha Nov 20, 2017
bf06851
Add test for checking warnings about rejected numbers.
MadaraUchiha Nov 21, 2017
9d29f0c
Fix failing symbol rejection test.
MadaraUchiha Nov 21, 2017
481c7f1
Make test lines wrap at 80 characters or less.
MadaraUchiha Nov 22, 2017
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20 changes: 17 additions & 3 deletions lib/internal/process/promises.js
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Original file line number Diff line number Diff line change
Expand Up @@ -60,11 +60,25 @@ function setupPromises(scheduleMicrotasks) {
}

function emitWarning(uid, reason) {
try {
if (reason instanceof Error) {
process.emitWarning(reason.stack, 'UnhandledPromiseRejectionWarning');
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So I guess the only downfall to doing it this way is it won't include any additional properties added on to the Error object. Any reason to do this vs using util.inspect()?

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Just that I wasn't aware of util.inspect(). I went with what the rest of the code did in the same function.

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Namely, Node doesn't show this information for synchronous errors:

// test.js
var e = new Error("error");
e.foo = "bar";
throw e;
~/test/test.js:3
throw e;
^

Error: error
    at Object.<anonymous> (/Users/benjamin/Downloads/test.js:1:71)
    at Module._compile (module.js:573:30)
    at Object.Module._extensions..js (module.js:584:10)
    at Module.load (module.js:507:32)
    at tryModuleLoad (module.js:470:12)
    at Function.Module._load (module.js:462:3)
    at Function.Module.runMain (module.js:609:10)
    at startup (bootstrap_node.js:158:16)
    at bootstrap_node.js:598:3

} else {
process.emitWarning(
safeToString(reason), 'UnhandledPromiseRejectionWarning'
);
}
} catch (e) {
// ignored
}

const warning = new Error(
`Unhandled promise rejection (rejection id: ${uid}): ` +
safeToString(reason));
'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';
warning.id = uid;
try {
if (reason instanceof Error) {
warning.stack = reason.stack;
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18 changes: 18 additions & 0 deletions test/message/unhandled_promise_trace_warnings.out
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Original file line number Diff line number Diff line change
@@ -1,3 +1,21 @@
(node:*) UnhandledPromiseRejectionWarning: Error: This was rejected
at * (*test*message*unhandled_promise_trace_warnings.js:*)
at *
at *
at *
at *
at *
at *
at *
at *
at *
at *
at *
at *
at *
at *
at *
at *
(node:*) Error: This was rejected
at * (*test*message*unhandled_promise_trace_warnings.js:*)
at *
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7 changes: 5 additions & 2 deletions test/parallel/test-promises-unhandled-proxy-rejections.js
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Expand Up @@ -6,8 +6,11 @@ const expectedDeprecationWarning = 'Unhandled promise rejections are ' +
'rejections that are not handled will ' +
'terminate the Node.js process with a ' +
'non-zero exit code.';
const expectedPromiseWarning = 'Unhandled promise rejection (rejection id: ' +
'1): [object Object]';
const expectedPromiseWarning = '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: 1)';

function throwErr() {
throw new Error('Error from proxy');
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13 changes: 10 additions & 3 deletions test/parallel/test-promises-unhandled-symbol-rejections.js
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@@ -1,17 +1,24 @@
'use strict';
const common = require('../common');

const expectedValueWarning = 'Symbol()';
const expectedDeprecationWarning = '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.';
const expectedPromiseWarning = 'Unhandled promise rejection (rejection id: ' +
'1): Symbol()';
const expectedPromiseWarning = '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: 1)';

common.expectWarning({
DeprecationWarning: expectedDeprecationWarning,
UnhandledPromiseRejectionWarning: expectedPromiseWarning,
UnhandledPromiseRejectionWarning: [
expectedPromiseWarning,
expectedValueWarning
],
});

// ensure this doesn't crash
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37 changes: 31 additions & 6 deletions test/parallel/test-promises-warning-on-unhandled-rejection.js
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Expand Up @@ -12,18 +12,43 @@ let b = 0;
process.on('warning', common.mustCall((warning) => {
switch (b++) {
case 0:
assert.strictEqual(warning.name, 'UnhandledPromiseRejectionWarning');
assert(/Unhandled promise rejection/.test(warning.message));
// String rejection error displayed
assert.strictEqual(warning.message, 'This was rejected');
break;
case 1:
assert.strictEqual(warning.name, 'DeprecationWarning');
// Warning about rejection not being handled (will be next tick)
assert.strictEqual(warning.name, 'UnhandledPromiseRejectionWarning');
assert(
/Unhandled promise rejection/.test(warning.message),
'Expected warning message to contain "Unhandled promise rejection" ' +
'but did not. Had "' + warning.message + '" instead.'
);
break;
case 2:
// One time deprecation warning, first unhandled rejection
assert.strictEqual(warning.name, 'DeprecationWarning');
break;
case 3:
// Number rejection error displayed. Note it's been stringified
assert.strictEqual(warning.message, '42');
break;
case 4:
// Unhandled rejection warning (won't be handled next tick)
assert.strictEqual(warning.name, 'UnhandledPromiseRejectionWarning');
assert(
/Unhandled promise rejection/.test(warning.message),
'Expected warning message to contain "Unhandled promise rejection" ' +
'but did not. Had "' + warning.message + '" instead.'
);
break;
case 5:
// Rejection handled asynchronously.
assert.strictEqual(warning.name, 'PromiseRejectionHandledWarning');
assert(/Promise rejection was handled asynchronously/
.test(warning.message));
}
}, 3));
}, 6));

const p = Promise.reject('This was rejected');
setImmediate(common.mustCall(() => p.catch(() => {})));
const p = Promise.reject('This was rejected'); // Reject with a string
setImmediate(common.mustCall(() => p.catch(() => { })));
Promise.reject(42); // Reject with a number