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assert: improve AssertionError in case of "Errors" #15025

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assert: improve AssertionError in case of "Errors" #15025

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23 changes: 14 additions & 9 deletions lib/internal/errors.js
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Original file line number Diff line number Diff line change
Expand Up @@ -35,21 +35,26 @@ class AssertionError extends Error {
if (typeof options !== 'object' || options === null) {
throw new exports.TypeError('ERR_INVALID_ARG_TYPE', 'options', 'object');
}
if (options.message) {
super(options.message);
var { actual, expected, message, operator, stackStartFunction } = options;
if (message) {
super(message);
} else {
if (actual && actual.stack && actual instanceof Error)
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Isn't actual instanceof Error itself enough?

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@BridgeAR BridgeAR Aug 26, 2017 •
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It is but it has a performance implication (it might not be important because it is only about errors but it is something that I always like to consider).

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Hmmm.. actually, I believe .stack is a getter isn't it? It will have a performance impact also.

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@BridgeAR BridgeAR Aug 26, 2017 •
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@jasnell util.inspect will look at the stack as well. The first call to the stack is heavy and it does not matter if it is done here or later on (well it is actually not anymore as we only pass a string through instead of the error but the performance for the error will stay the same as before and the average case wont have any negative hit).

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So yes, it would be faster for Error objects (the instanceof check is added on top of the stack access) but slower for the average case.

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Yeah. Hmm. It's likely fine. Doing it the same way internal/util isError does would likely be ok also but I'm good with it :)

actual = `${actual.name}: ${actual.message}`;
if (expected && expected.stack && expected instanceof Error)
expected = `${expected.name}: ${expected.message}`;
if (util === null) util = require('util');
super(`${util.inspect(options.actual).slice(0, 128)} ` +
`${options.operator} ${util.inspect(options.expected).slice(0, 128)}`);
super(`${util.inspect(actual).slice(0, 128)} ` +
`${operator} ${util.inspect(expected).slice(0, 128)}`);
}

this.generatedMessage = !options.message;
this.generatedMessage = !message;
this.name = 'AssertionError [ERR_ASSERTION]';
this.code = 'ERR_ASSERTION';
this.actual = options.actual;
this.expected = options.expected;
this.operator = options.operator;
Error.captureStackTrace(this, options.stackStartFunction);
this.actual = actual;
this.expected = expected;
this.operator = operator;
Error.captureStackTrace(this, stackStartFunction);
}
}

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9 changes: 9 additions & 0 deletions test/parallel/test-assert.js
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Expand Up @@ -715,3 +715,12 @@ assert.throws(() => {
}));
});
}

common.expectsError(
() => assert.strictEqual(new Error('foo'), new Error('foobar')),
{
code: 'ERR_ASSERTION',
type: assert.AssertionError,
message: /^'Error: foo' === 'Error: foobar'$/
}
);