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assert: improve class instance errors · nodejs/node@ace3f16 · GitHub

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assert: improve class instance errors
This improves `assert.throws()` and `assert.rejects()` in case error classes are used as validation for the expected error. In case of a failure it will now throw an `AssertionError` instead of the received error if the check fails. That error has the received error as actual property and the expected property is set to the expected error class. The error message should help users to identify the problem faster than before by providing extra context what went wrong. PR-URL: #28263 Reviewed-By: Rich Trott <rtrott@gmail.com> Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>
1 parent eb05d68 commit ace3f16

2 files changed

Lines changed: 73 additions & 25 deletions

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‎lib/assert.js‎

Lines changed: 24 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -20,7 +20,7 @@
2020

2121
'use strict';
2222

23-
const { Object } = primordials;
23+
const { Object, ObjectPrototype } = primordials;
2424

2525
const { Buffer } = require('buffer');
2626
const { codes: {
@@ -36,6 +36,7 @@ const { inspect } = require('internal/util/inspect');
3636
const { isPromise, isRegExp } = require('internal/util/types');
3737
const { EOL } = require('internal/constants');
3838
const { NativeModule } = require('internal/bootstrap/loaders');
39+
const { isError } = require('internal/util');
3940

4041
const errorCache = new Map();
4142

@@ -561,6 +562,8 @@ function compareExceptionKey(actual, expected, key, message, keys, fn) {
561562
}
562563

563564
function expectedException(actual, expected, message, fn) {
565+
let generatedMessage = false;
566+
564567
if (typeof expected !== 'function') {
565568
// Handle regular expressions.
566569
if (isRegExp(expected)) {
@@ -618,8 +621,26 @@ function expectedException(actual, expected, message, fn) {
618621
if (expected.prototype !== undefined && actual instanceof expected) {
619622
return;
620623
}
621-
if (Error.isPrototypeOf(expected)) {
622-
throw actual;
624+
if (ObjectPrototype.isPrototypeOf(Error, expected)) {
625+
if (!message) {
626+
generatedMessage = true;
627+
message = 'The error is expected to be an instance of ' +
628+
`"${expected.name}". Received `;
629+
if (isError(actual)) {
630+
message += `"${actual.name}"`;
631+
} else {
632+
message += `"${inspect(actual, { depth: -1 })}"`;
633+
}
634+
}
635+
const err = new AssertionError({
636+
actual,
637+
expected,
638+
message,
639+
operator: fn.name,
640+
stackStartFn: fn
641+
});
642+
err.generatedMessage = generatedMessage;
643+
throw err;
623644
}
624645

625646
// Check validation functions return value.

‎test/parallel/test-assert.js‎

Lines changed: 49 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -123,16 +123,19 @@ assert.throws(() => thrower(a.AssertionError));
123123
assert.throws(() => thrower(TypeError));
124124

125125
// When passing a type, only catch errors of the appropriate type.
126-
{
127-
let threw = false;
128-
try {
129-
a.throws(() => thrower(TypeError), a.AssertionError);
130-
} catch (e) {
131-
threw = true;
132-
assert.ok(e instanceof TypeError, 'type');
126+
assert.throws(
127+
() => a.throws(() => thrower(TypeError), a.AssertionError),
128+
{
129+
generatedMessage: true,
130+
actual: new TypeError({}),
131+
expected: a.AssertionError,
132+
code: 'ERR_ASSERTION',
133+
name: 'AssertionError',
134+
operator: 'throws',
135+
message: 'The error is expected to be an instance of "AssertionError". ' +
136+
'Received "TypeError"'
133137
}
134-
assert.ok(threw, 'a.throws with an explicit error is eating extra errors');
135-
}
138+
);
136139

137140
// doesNotThrow should pass through all errors.
138141
{
@@ -237,20 +240,27 @@ a.throws(() => thrower(TypeError), (err) => {
237240

238241
// https://github.com/nodejs/node/issues/3188
239242
{
240-
let threw = false;
241-
let AnotherErrorType;
242-
try {
243-
const ES6Error = class extends Error {};
244-
AnotherErrorType = class extends Error {};
245-
246-
assert.throws(() => { throw new AnotherErrorType('foo'); }, ES6Error);
247-
} catch (e) {
248-
threw = true;
249-
assert(e instanceof AnotherErrorType,
250-
`expected AnotherErrorType, received ${e}`);
251-
}
243+
let actual;
244+
assert.throws(
245+
() => {
246+
const ES6Error = class extends Error {};
247+
const AnotherErrorType = class extends Error {};
252248

253-
assert.ok(threw);
249+
assert.throws(() => {
250+
actual = new AnotherErrorType('foo');
251+
throw actual;
252+
}, ES6Error);
253+
},
254+
(err) => {
255+
assert.strictEqual(
256+
err.message,
257+
'The error is expected to be an instance of "ES6Error". ' +
258+
'Received "Error"'
259+
);
260+
assert.strictEqual(err.actual, actual);
261+
return true;
262+
}
263+
);
254264
}
255265

256266
// Check messages from assert.throws().
@@ -1299,3 +1309,20 @@ assert.throws(
12991309
assert(!err2.stack.includes('hidden'));
13001310
})();
13011311
}
1312+
1313+
assert.throws(
1314+
() => assert.throws(() => { throw Symbol('foo'); }, RangeError),
1315+
{
1316+
message: 'The error is expected to be an instance of "RangeError". ' +
1317+
'Received "Symbol(foo)"'
1318+
}
1319+
);
1320+
1321+
assert.throws(
1322+
// eslint-disable-next-line no-throw-literal
1323+
() => assert.throws(() => { throw [1, 2]; }, RangeError),
1324+
{
1325+
message: 'The error is expected to be an instance of "RangeError". ' +
1326+
'Received "[Array]"'
1327+
}
1328+
);

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