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assert: support custom errors · nodejs/node@e13d1df · GitHub

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assert: support custom errors
This commit adds special handling of Error instances when passed as the message argument to assert functions. With this commit, if an Error is passed as the message, then that Error is thrown instead of an AssertionError. PR-URL: #15304 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
1 parent a10856a commit e13d1df

4 files changed

Lines changed: 93 additions & 18 deletions

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‎doc/api/assert.md‎

Lines changed: 41 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -101,7 +101,9 @@ assert.deepEqual(obj1, obj4);
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If the values are not equal, an `AssertionError` is thrown with a `message`
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property set equal to the value of the `message` parameter. If the `message`
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parameter is undefined, a default error message is assigned.
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parameter is undefined, a default error message is assigned. If the `message`
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parameter is an instance of an `Error` then it will be thrown instead of the
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`AssertionError`.
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## assert.deepStrictEqual(actual, expected[, message])
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<!-- YAML
@@ -176,7 +178,9 @@ assert.deepStrictEqual(NaN, NaN);
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If the values are not equal, an `AssertionError` is thrown with a `message`
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property set equal to the value of the `message` parameter. If the `message`
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parameter is undefined, a default error message is assigned.
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parameter is undefined, a default error message is assigned. If the `message`
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parameter is an instance of an `Error` then it will be thrown instead of the
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`AssertionError`.
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## assert.doesNotThrow(block[, error][, message])
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<!-- YAML
@@ -270,7 +274,9 @@ assert.equal({ a: { b: 1 } }, { a: { b: 1 } });
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If the values are not equal, an `AssertionError` is thrown with a `message`
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property set equal to the value of the `message` parameter. If the `message`
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parameter is undefined, a default error message is assigned.
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parameter is undefined, a default error message is assigned. If the `message`
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parameter is an instance of an `Error` then it will be thrown instead of the
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`AssertionError`.
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## assert.fail([message])
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## assert.fail(actual, expected[, message[, operator[, stackStartFunction]]])
@@ -284,13 +290,15 @@ added: v0.1.21
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* `stackStartFunction` {function} (default: `assert.fail`)
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Throws an `AssertionError`. If `message` is falsy, the error message is set as
287-
the values of `actual` and `expected` separated by the provided `operator`.
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If just the two `actual` and `expected` arguments are provided, `operator` will
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default to `'!='`. If `message` is provided only it will be used as the error
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message, the other arguments will be stored as properties on the thrown object.
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If `stackStartFunction` is provided, all stack frames above that function will
292-
be removed from stacktrace (see [`Error.captureStackTrace`]). If no arguments
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are given, the default message `Failed` will be used.
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the values of `actual` and `expected` separated by the provided `operator`. If
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the `message` parameter is an instance of an `Error` then it will be thrown
295+
instead of the `AssertionError`. If just the two `actual` and `expected`
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arguments are provided, `operator` will default to `'!='`. If `message` is
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provided only it will be used as the error message, the other arguments will be
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stored as properties on the thrown object. If `stackStartFunction` is provided,
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all stack frames above that function will be removed from stacktrace (see
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[`Error.captureStackTrace`]). If no arguments are given, the default message
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`Failed` will be used.
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```js
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const assert = require('assert');
@@ -303,6 +311,9 @@ assert.fail(1, 2, 'fail');
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assert.fail(1, 2, 'whoops', '>');
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// AssertionError [ERR_ASSERTION]: whoops
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assert.fail(1, 2, new TypeError('need array'));
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// TypeError: need array
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```
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*Note*: Is the last two cases `actual`, `expected`, and `operator` have no
@@ -414,7 +425,9 @@ assert.notDeepEqual(obj1, obj4);
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If the values are deeply equal, an `AssertionError` is thrown with a `message`
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property set equal to the value of the `message` parameter. If the `message`
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parameter is undefined, a default error message is assigned.
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parameter is undefined, a default error message is assigned. If the `message`
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parameter is an instance of an `Error` then it will be thrown instead of the
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`AssertionError`.
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## assert.notDeepStrictEqual(actual, expected[, message])
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<!-- YAML
@@ -455,9 +468,11 @@ assert.notDeepStrictEqual({ a: 1 }, { a: '1' });
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// OK
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```
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If the values are deeply and strictly equal, an `AssertionError` is thrown
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with a `message` property set equal to the value of the `message` parameter. If
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the `message` parameter is undefined, a default error message is assigned.
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If the values are deeply and strictly equal, an `AssertionError` is thrown with
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a `message` property set equal to the value of the `message` parameter. If the
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`message` parameter is undefined, a default error message is assigned. If the
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`message` parameter is an instance of an `Error` then it will be thrown instead
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of the `AssertionError`.
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## assert.notEqual(actual, expected[, message])
463478
<!-- YAML
@@ -485,7 +500,9 @@ assert.notEqual(1, '1');
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If the values are equal, an `AssertionError` is thrown with a `message`
487502
property set equal to the value of the `message` parameter. If the `message`
488-
parameter is undefined, a default error message is assigned.
503+
parameter is undefined, a default error message is assigned. If the `message`
504+
parameter is an instance of an `Error` then it will be thrown instead of the
505+
`AssertionError`.
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490507
## assert.notStrictEqual(actual, expected[, message])
491508
<!-- YAML
@@ -513,7 +530,9 @@ assert.notStrictEqual(1, '1');
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514531
If the values are strictly equal, an `AssertionError` is thrown with a
515532
`message` property set equal to the value of the `message` parameter. If the
516-
`message` parameter is undefined, a default error message is assigned.
533+
`message` parameter is undefined, a default error message is assigned. If the
534+
`message` parameter is an instance of an `Error` then it will be thrown instead
535+
of the `AssertionError`.
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## assert.ok(value[, message])
519538
<!-- YAML
@@ -527,7 +546,9 @@ Tests if `value` is truthy. It is equivalent to
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If `value` is not truthy, an `AssertionError` is thrown with a `message`
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property set equal to the value of the `message` parameter. If the `message`
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parameter is `undefined`, a default error message is assigned.
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parameter is `undefined`, a default error message is assigned. If the `message`
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parameter is an instance of an `Error` then it will be thrown instead of the
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`AssertionError`.
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```js
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const assert = require('assert');
@@ -570,7 +591,9 @@ assert.strictEqual(1, '1');
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571592
If the values are not strictly equal, an `AssertionError` is thrown with a
572593
`message` property set equal to the value of the `message` parameter. If the
573-
`message` parameter is undefined, a default error message is assigned.
594+
`message` parameter is undefined, a default error message is assigned. If the
595+
`message` parameter is an instance of an `Error` then it will be thrown instead
596+
of the `AssertionError`.
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575598
## assert.throws(block[, error][, message])
576599
<!-- YAML

‎lib/assert.js‎

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Original file line numberDiff line numberDiff line change
@@ -38,6 +38,8 @@ const assert = module.exports = ok;
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// display purposes.
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4040
function innerFail(actual, expected, message, operator, stackStartFunction) {
41+
if (message instanceof Error) throw message;
42+
4143
throw new errors.AssertionError({
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message,
4345
actual,

‎test/parallel/test-assert-fail.js‎

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Original file line numberDiff line numberDiff line change
@@ -28,6 +28,17 @@ common.expectsError(() => {
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expected: undefined
2929
});
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31+
// One arg = Error
32+
common.expectsError(() => {
33+
assert.fail(new TypeError('custom message'));
34+
}, {
35+
type: TypeError,
36+
message: 'custom message',
37+
operator: undefined,
38+
actual: undefined,
39+
expected: undefined
40+
});
41+
3142
// Two args only, operator defaults to '!='
3243
common.expectsError(() => {
3344
assert.fail('first', 'second');
@@ -52,6 +63,17 @@ common.expectsError(() => {
5263
expected: 'ignored'
5364
});
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66+
// Three args with custom Error
67+
common.expectsError(() => {
68+
assert.fail(typeof 1, 'object', new TypeError('another custom message'));
69+
}, {
70+
type: TypeError,
71+
message: 'another custom message',
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operator: undefined,
73+
actual: 'number',
74+
expected: 'object'
75+
});
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5577
// No third arg (but a fourth arg)
5678
common.expectsError(() => {
5779
assert.fail('first', 'second', undefined, 'operator');

‎test/parallel/test-assert.js‎

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Original file line numberDiff line numberDiff line change
@@ -645,6 +645,34 @@ try {
645645
'Message incorrectly marked as generated');
646646
}
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648+
{
649+
let threw = false;
650+
const rangeError = new RangeError('my range');
651+
652+
// verify custom errors
653+
try {
654+
assert.strictEqual(1, 2, rangeError);
655+
} catch (e) {
656+
assert.strictEqual(e, rangeError);
657+
threw = true;
658+
assert.ok(e instanceof RangeError, 'Incorrect error type thrown');
659+
}
660+
assert.ok(threw);
661+
threw = false;
662+
663+
// verify AssertionError is the result from doesNotThrow with custom Error
664+
try {
665+
assert.doesNotThrow(() => {
666+
throw new TypeError('wrong type');
667+
}, TypeError, rangeError);
668+
} catch (e) {
669+
threw = true;
670+
assert.ok(e.message.includes(rangeError.message));
671+
assert.ok(e instanceof assert.AssertionError);
672+
}
673+
assert.ok(threw);
674+
}
675+
648676
{
649677
// Verify that throws() and doesNotThrow() throw on non-function block
650678
function typeName(value) {

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