Error Wrapping in Go

Error wrapping in Go enhances error handling by providing richer context about errors. Introduced in Go 1.13, it allows for detailed debugging and seamless error traceability.

Basic Error Wrapping

Using the fmt.Errorf function, you can wrap errors with additional information:

package main

import (
	"errors"
	"fmt"
)

func main() {
	originalErr := errors.New("original error")
	wrappedErr := fmt.Errorf("additional context: %w", originalErr)

	fmt.Println(wrappedErr)
}

Retrieving Original Errors

Use errors.Is to check if an error matches a particular error in the wrapped chain:

package main

import (
	"errors"
	"fmt"
)

func main() {
	originalErr := errors.New("original error")
	wrappedErr := fmt.Errorf("additional context: %w", originalErr)

	if errors.Is(wrappedErr, originalErr) {
		fmt.Println("The wrapped error contains the original error")
	}
}

Unwrapping Errors

To retrieve the original error, use the errors.Unwrap function:

package main

import (
	"errors"
	"fmt"
)

func main() {
	originalErr := errors.New("original error")
	wrappedErr := fmt.Errorf("additional context: %w", originalErr)

	unwrappedErr := errors.Unwrap(wrappedErr)
	fmt.Println(unwrappedErr) // Prints: "original error"
}

Best Practices

• Provide Context: Always wrap errors with context that helps in understanding the failure.
• Use Custom Error Types: Define custom error types for specific error classes in your application to provide more structured error handling.
• Consistent Error Wrapping: Standardize how errors are wrapped across your codebase to simplify debugging and logging.

Common Pitfalls

• Over-Wrapping Errors: Avoid over-wrapping errors with redundant context, which can make error messages verbose and harder to read.
• Ignoring Error Chains: Failing to propagate error chains through wrapping can make debugging challenging when errors occur in deeper layers of the application.
• Improper Error Matching: Ensure usage of errors.Is to correctly identify specific errors rather than simply matching error strings.

Performance Tips

• Granular Error Wrapping: Wrap errors only when necessary to reduce performance overhead of constructing additional error objects.
• Erroneous Path Minimization: Strive to avoid errors in critical paths to reduce the frequency of error wrapping and handling operations.
• Adequate Logging: Integrate well-placed logging for wrapped errors to ease tracking and diagnostics, maintaining application performance.