How Can I Effectively Handle Errors in Go's Multi-Level Abstractions?

Handling Errors in Multi-Level Abstractions in Go

Error handling in multi-level abstractions can become cumbersome when errors are repeatedly passed up the chain, leading to duplicate logs and lost context.

Annotating Errors

Annotating errors is a recommended approach. It involves creating a new error value that wraps the original error, providing additional context. The errors package provides Wrap() and Cause() functions for this purpose.

In the given example:

// ObjectThreeHiggerLevel
func (oTh *ObjectThreeHiggerLevel) CheckObjectTwoIsReady() error {
    if err := oTh.ObjectTwoHigherLevel.CheckObjectOneIsReady(); err != nil {
        return errors.Wrap(err, "Object3 illegal state: Object2 is invalid")
    }
    return nil
}

The ObjectThreeHiggerLevel annotates the error from ObjectTwoHigherLevel with additional context.

"Extending" Errors

An alternative approach is to "extend" errors using fmt.Errorf(). While it doesn't provide error unwrapping capabilities, it allows you to create custom error messages with added context:

// ObjectThreeHiggerLevel
func (oTh *ObjectThreeHiggerLevel) CheckObjectTwoIsReady() error {
    if err := oTh.ObjectTwoHigherLevel.CheckObjectOneIsReady(); err != nil {
        return fmt.Errorf("Object3 illegal state: %v", err)
    }
    return nil
}

Delegating or Handling Errors

When handling errors, it's important to decide whether to handle them or delegate them to a higher level. If an error is not handled, it should be delegated with added context to avoid losing information or causing duplicate logs.

In the example:

// ObjectThreeHiggerLevel
func (oTh *ObjectThreeHiggerLevel) CheckObjectTwoIsReady() error {
    if err := oTh.ObjectTwoHigherLevel.CheckObjectOneIsReady(); err != nil {
        if err := oTh.HandleError(err); err != nil {
            // Error handling failed, log and return original error
            return errors.Wrapf(err, "Object3 failed to handle error: %v", err)
        }
        return nil
    }
    return nil
}

In this example, HandleError() attempts to handle the error. If it fails, the original error is wrapped and returned.

Avoid Duplicate Logs

Annotating or extending errors with context ensures that when an error is propagated up the stack, it contains all the necessary information for meaningful logging and error handling. This prevents duplicate logs and helps in understanding the root cause of an issue.

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