| commit | 52f73bd1b9707bccddb728b3043e1ff43e8895a8 | [log] [tgz] |
|---|---|---|
| author | Brian Flad <bflad417@gmail.com> | Mon Feb 19 17:27:35 2018 |
| committer | Brian Flad <bflad417@gmail.com> | Mon Feb 19 17:27:35 2018 |
| tree | 7f9c5b683239d4b16f480457e945c9fada6b5a58 | |
| parent | b7773ae218740a7be65057fc60b366a49b538a44 [diff] |
Implement sort interface for error messages
go-multierror is a package for Go that provides a mechanism for representing a list of error values as a single error.
This allows a function in Go to return an error that might actually be a list of errors. If the caller knows this, they can unwrap the list and access the errors. If the caller doesn't know, the error formats to a nice human-readable format.
go-multierror implements the errwrap interface so that it can be used with that library, as well.
Install using go get github.com/hashicorp/go-multierror.
Full documentation is available at http://godoc.org/github.com/hashicorp/go-multierror
go-multierror is easy to use and purposely built to be unobtrusive in existing Go applications/libraries that may not be aware of it.
Building a list of errors
The Append function is used to create a list of errors. This function behaves a lot like the Go built-in append function: it doesn't matter if the first argument is nil, a multierror.Error, or any other error, the function behaves as you would expect.
var result error
if err := step1(); err != nil {
result = multierror.Append(result, err)
}
if err := step2(); err != nil {
result = multierror.Append(result, err)
}
return result
Customizing the formatting of the errors
By specifying a custom ErrorFormat, you can customize the format of the Error() string function:
var result *multierror.Error // ... accumulate errors here, maybe using Append if result != nil { result.ErrorFormat = func([]error) string { return "errors!" } }
Accessing the list of errors
multierror.Error implements error so if the caller doesn‘t know about multierror, it will work just fine. But if you’re aware a multierror might be returned, you can use type switches to access the list of errors:
if err := something(); err != nil { if merr, ok := err.(*multierror.Error); ok { // Use merr.Errors } }
Returning a multierror only if there are errors
If you build a multierror.Error, you can use the ErrorOrNil function to return an error implementation only if there are errors to return:
var result *multierror.Error // ... accumulate errors here // Return the `error` only if errors were added to the multierror, otherwise // return nil since there are no errors. return result.ErrorOrNil()