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util: show SuppressedError's error/suppressed properties on inspect #66159

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util: show SuppressedError's error/suppressed properties on inspect #66159

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10 changes: 10 additions & 0 deletions lib/internal/util/inspect.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1990,6 +1990,16 @@ function formatError(err, constructor, tag, ctx, keys) {
// If errors is a getter that throws, we ignore the error.
}

// Print the wrapped errors of a SuppressedError.
if (ObjectPrototypeHasOwnProperty(err, 'error') &&
(keys.length === 0 || !ArrayPrototypeIncludes(keys, 'error'))) {
ArrayPrototypePush(keys, 'error');
}
if (ObjectPrototypeHasOwnProperty(err, 'suppressed') &&
(keys.length === 0 || !ArrayPrototypeIncludes(keys, 'suppressed'))) {
ArrayPrototypePush(keys, 'suppressed');
}

stack = improveStack(stack, constructor, name, tag);

// Ignore the error message if it's contained in the stack.
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47 changes: 47 additions & 0 deletions test/parallel/test-util-inspect.js
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Original file line number Diff line number Diff line change
Expand Up @@ -735,6 +735,53 @@ assert.strictEqual(util.inspect(-5e-324), '-5e-324');
Error.stackTraceLimit = stackTraceLimit;
}

{
// The `error` and `suppressed` properties of a SuppressedError should be
// shown during inspection, same as `cause` and AggregateError's `errors`.
const { stackTraceLimit } = Error;
Error.stackTraceLimit = 0;

const disposeError = new Error('dispose error');
const bodyError = new Error('body error');
const suppressedError = new SuppressedError(
disposeError,
bodyError,
'An error was suppressed during disposal',
);

assert.strictEqual(
util.inspect(suppressedError),
'[SuppressedError: An error was suppressed during disposal] ' +
'{\n [error]: [Error: dispose error],\n [suppressed]: [Error: body error]\n}',
);

// Nested SuppressedErrors (multiple failed disposals) must recurse.
const outer = new SuppressedError(
new Error('second dispose error'),
suppressedError,
'outer',
);
assert.strictEqual(
util.inspect(outer),
'[SuppressedError: outer] {\n' +
' [error]: [Error: second dispose error],\n' +
' [suppressed]: [SuppressedError: An error was suppressed during disposal] {\n' +
' [error]: [Error: dispose error],\n' +
' [suppressed]: [Error: body error]\n' +
' }\n' +
'}',
);

const custom = new Error('No own error/suppressed property');
Object.setPrototypeOf(custom, suppressedError);
Comment on lines +775 to +776

@ljharb ljharb Sep 20, 2026

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why not:

Suggested change
const custom = new Error('No own error/suppressed property');
Object.setPrototypeOf(custom, suppressedError);
const custom = new SuppressedError('No own error/suppressed property');

?

@agape1225 agape1225 Sep 21, 2026

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Thanks for the suggestion! I'd like to keep the original version, though — SuppressedError's signature is (error, suppressed, message), so with just one argument that string becomes error, not the message, and both error/suppressed end up as own properties (same as cause above). That means it wouldn't exercise the 'no own property' case this block is meant to test. Happy to tweak the comment or naming if that'd help.

assert.strictEqual(
util.inspect(custom),
'[SuppressedError: No own error/suppressed property]',
);

Error.stackTraceLimit = stackTraceLimit;
}

{
const tmp = Error.stackTraceLimit;
// Force stackTraceLimit = 0 for this test, but make it non-enumerable
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