Understanding the default error type in v5.

I can throw anything, i.e.

throw 5

throw 5

. I log the error and is indeed 5 with type number but the error type is annotated as

Error | null

Error | null

. This can introduce runtime errors when narrowing the union and performing operations on the value such as

// jobQuery.error is Error | null;
if (jobQuery.error === null) return
const message = jobQuery.error.message.toLocaleLowerCase() // Runtime crash because it's a number, not a string

// jobQuery.error is Error | null;
if (jobQuery.error === null) return
const message = jobQuery.error.message.toLocaleLowerCase() // Runtime crash because it's a number, not a string

Is this intentional? Maybe my configuration is wrong or I'm doing something wrong. The old unknown type avoided the problem by typing errors in the most generic way possible.

TanStack•13mo ago•

10 replies

specific-silver

Understanding the default error type in v5.

I can throw anything, i.e.

throw 5

throw 5

. I log the error and is indeed 5 with type number but the error type is annotated as

Error | null

Error | null

. This can introduce runtime errors when narrowing the union and performing operations on the value such as

// jobQuery.error is Error | null;
if (jobQuery.error === null) return
const message = jobQuery.error.message.toLocaleLowerCase() // Runtime crash because it's a number, not a string

// jobQuery.error is Error | null;
if (jobQuery.error === null) return
const message = jobQuery.error.message.toLocaleLowerCase() // Runtime crash because it's a number, not a string

Is this intentional? Maybe my configuration is wrong or I'm doing something wrong. The old unknown type avoided the problem by typing errors in the most generic way possible.

Understanding the default error type in v5.

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