Go Function Parameters: Errors or Panics for Validation?

Function Parameter Validation in Go: Errors vs. Panics

When designing functions in Go, one of the key decisions is how to handle invalid or erroneous parameter values. Should errors be returned or should panics be used?

Error Handling with Return Codes

Returning errors is generally considered good practice for parameter validation in Go. This allows the caller to handle the error gracefully and decide how to proceed. For example:

func ValidateNumber(num int) error {
    if num  100 {
        return errors.New("Invalid number")
    }

    return nil
}

This approach is preferred when the caller can reasonably expect to encounter such errors and can handle them appropriately.

Panics for Serious Errors

Panics, on the other hand, are typically used for unrecoverable errors that indicate a fundamental problem with the program logic. In the context of parameter validation, panics can be used when a nil pointer or out-of-range value would result in a serious runtime error. For example:

func ValidatePointer(p *int) {
    if p == nil {
        panic("Nil pointer")
    }
}

Guidelines for Choosing Between Errors vs. Panics

The choice between errors and panics for parameter validation depends on the nature of the error:

• Errors: Use errors for errors that the caller can reasonably handle.
• Panics: Use panics for unrecoverable errors that indicate a serious problem with the program logic, such as nil pointers or out-of-range values.

Limitations of Return Errors

While using errors for parameter validation is generally a good approach, it can lead to overly verbose code if there are multiple validation checks. Additionally, the caller must handle all errors, even if they are not relevant to their use case.

"Just Let it Fail" Approach

The "just let it fail" approach, where errors are not handled explicitly, can be tempting. However, this can lead to unpredictable and potentially catastrophic behavior if errors occur. It is generally not recommended for critical functions or in production code.

Conclusion

In summary, using errors for parameter validation is generally preferred in Go, as it allows the caller to handle errors gracefully. Panics should be reserved for serious, unrecoverable errors that indicate fundamental problems with the program logic. The guidelines outlined above can help you make informed decisions about when to use errors vs. panics in your Go code.

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