fix(nestjs): Add support for Symbol as event name #17785

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stefanvanderwolf wants to merge 1 commit into getsentry:develop

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fix(nestjs): Add support for Symbol as event name #17785

stefanvanderwolf wants to merge 1 commit into getsentry:develop from stefanvanderwolf:fix/event-name-symbol

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@stefanvanderwolf stefanvanderwolf commented Sep 25, 2025 •

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The @OnEvent decorator accepts the following types for its argument:

string | symbol | Array<string | symbol>

If a Symbol is included in an array, the code to get the eventName will throw a TypeError (String(event)) This occurs because JavaScript’s
Array.prototype.join internally calls ToString on each array element. Per the specification, ToString(Symbol) is not allowed and results in a TypeError.

To avoid this issue, do not rely on String(array) or .join() on arrays containing symbols directly. Instead, explicitly convert each element to a string while handling symbols safely.

I couldn't find a way to test adding multiple @OnEvent so the second part can be tested. It didn't have any tests before (as far as I can tell), but would be nice to add them.

doc: https://tc39.es/ecma262/multipage/indexed-collections.html#sec-array.prototype.join
doc: https://tc39.es/ecma262/multipage/abstract-operations.html#sec-tostring

@stefanvanderwolf


 fix(nestjs): Add support for Symbol as event name

e116b39

The @onevent decorator accepts the following types for its argument:
```typescript
string | symbol | Array<string | symbol>
``
If a Symbol is included in an array, the code to get the eventName will
throw a TypeError (String(event)) This occurs because JavaScript’s
Array.prototype.join internally calls ToString on each array element.
Per the specification, ToString(Symbol) is not allowed and results in a
TypeError.
To avoid this issue, do not rely on String(array) or .join() on arrays
containing symbols directly. Instead, explicitly convert each element to
a string while handling symbols safely.
doc: https://tc39.es/ecma262/multipage/indexed-collections.html#sec-array.prototype.join
doc: https://tc39.es/ecma262/multipage/abstract-operations.html#sec-tostring

cursor[bot]

cursor bot reviewed

Sep 25, 2025

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packages/nestjs/src/integrations/sentry-nest-event-instrumentation.ts

} else if (Array.isArray(event)) {

return event.map(eventNameFromEvent).join(',');

} else return String(event);

}

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Bug: Symbol Handling Fails in Event Name Extraction

The eventNameFromEvent function at line 82 uses String(event) in its fallback, which throws a TypeError when the event is a Symbol. This prevents proper Symbol handling, contrary to the PR's intent.

Fix in Cursor Fix in Web