How Can I Prevent Infinite Loops When Handling Custom Errors in Go?

Non-Recursive Error Handling: Preventing Infinite Loops

In Go, exceptional situations are typically handled using error values, which implement the error interface. The Error() method of the interface returns a string describing the error.

However, when working with custom error types, it's essential to avoid recursion in the Error() method.

The Infinite Loop Problem

Consider a custom error type where the Error() method calls fmt.Sprint(e) to convert the error value to a string. This approach poses a potential problem:

type MyError struct {
    message string
}

func (e MyError) Error() string {
    return fmt.Sprint(e)
}

If you now try to print the error, an infinite loop occurs:

func main() {
    err := MyError{"Error!"}
    fmt.Println(err)
}

This happens because fmt.Sprint(e) calls e.Error(), which in turn calls fmt.Sprint(e) again, and so on.

Breaking the Recursion

To break the recursion, convert e to a value that doesn't have a String or Error method before passing it to fmt.Sprint:

func main() {
    err := MyError{"Error!"}
    fmt.Println(fmt.Sprint(float64(err)))
}

In this example, converting e to a float64 removes its String and Error methods, preventing the infinite loop.

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