How to Effectively Handle Errors in Go's Multi-Level Abstraction Hierarchies?

Handling Errors in a Multi-Level Abstraction Hierarchy in Go

In Go, when working with multiple levels of abstraction, error handling becomes critical for maintaining a clean and maintainable codebase. It's crucial to prevent duplicate error messages and ensure errors are handled in a meaningful way.

Wrap Errors

The recommended approach is to wrap errors using the errors package or similar tools. This technique involves creating a new error value that wraps the original error, providing context at each level of the abstraction hierarchy.

Annotating Errors Example

Consider the following example using the errors package:

func (o *ObjectOne) CheckValue() error {
    if o.someValue == 0 {
        return errors.New("Object1 illegal state: value is 0")
    }
    return nil
}

func (oT *ObjectTwoHigherLevel) CheckObjectOneIsReady() error {
    if err := oT.objectOne.CheckValue(); err != nil {
        return errors.Wrap(err, "Object2 illegal state: Object1 is invalid")
    }
    return nil
}

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

In this example, the errors are wrapped at each level, providing a clear trail of context leading to the root cause of the error.

fmt.Errorf() Extension

As an alternative to wrapping errors, you can also extend the error by using fmt.Errorf(). This approach is simpler but does not allow you to extract the original error.

func (o *ObjectOne) CheckValue() error {
    if o.someValue == 0 {
        return fmt.Errorf("Object1 illegal state: value is %d", o.someValue)
    }
    return nil
}

func (oT *ObjectTwoHigherLevel) CheckObjectOneIsReady() error {
    if err := oT.objectOne.CheckValue(); err != nil {
        return fmt.Errorf("Object2 illegal state: %v", err)
    }
    return nil
}

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

Error Handling vs. Delegation

It's important to consider whether an error should be handled or delegated to a higher level. Handling an error involves inspecting it and taking specific actions, while delegation passes the responsibility to the caller. Delegation is preferred if the caller is better equipped to handle the error or if the error is simply informative.

Log Error Messages

When logging error messages, ensure that you provide sufficient detail about the error and its context. Use the error's error string and any additional information available to clearly identify the root cause of the problem.

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