How to check if an error is wrapped or is original

[xxjapp]

Need method to check if error is wrapped

[davecheney]

If you had that method, what would that enable you to do? Why is it important for your program to be able to detect if an error value wraps another?

[xxjapp]

@davecheney

If I had the method, I could differentiate wrapped errors with call stack information and original errors without call stack information. For original errors I could add some call stack information by myself.

[xxjapp]

For wrapped errors, I think there is no need to wrap it again when wrapping error from other's source.

[puellanivis]

In general, either a source should guarantee that all of its errors are wrapped, or none of them are.
If you absolutely must work with a broken design, then the following code does what you want it to do. Writing a helper function to do the same would save you no complexity:

if causer, ok := err.(interface{ Cause() error }); ok {
  // value is wrapped
}

[xxjapp]

@puellanivis

Thank you for your detailed answer. For some reasons, I have to work with such a broken design from legacy source.

[puellanivis]

Tech Debt… we meet again old friend…