README
¶
go-multierror
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.
Installation and Docs
Install using go get github.com/hashicorp/go-multierror.
Full documentation is available at http://godoc.org/github.com/hashicorp/go-multierror
Usage
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()
Documentation
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Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func ListFormatFunc ¶
ListFormatFunc is a basic formatter that outputs the number of errors that occurred along with a bullet point list of the errors.
Types ¶
type Error ¶
type Error struct {
Errors []error
ErrorFormat ErrorFormatFunc
}
Error is an error type to track multiple errors. This is used to accumulate errors in cases and return them as a single "error".
func Append ¶
Append is a helper function that will append more errors onto an Error in order to create a larger multi-error.
If err is not a multierror.Error, then it will be turned into one. If any of the errs are multierr.Error, they will be flattened one level into err.
func (*Error) ErrorOrNil ¶
ErrorOrNil returns an error interface if this Error represents a list of errors, or returns nil if the list of errors is empty. This function is useful at the end of accumulation to make sure that the value returned represents the existence of errors.
func (*Error) WrappedErrors ¶
WrappedErrors returns the list of errors that this Error is wrapping. It is an implementatin of the errwrap.Wrapper interface so that multierror.Error can be used with that library.
This method is not safe to be called concurrently and is no different than accessing the Errors field directly. It is implementd only to satisfy the errwrap.Wrapper interface.
type ErrorFormatFunc ¶
ErrorFormatFunc is a function callback that is called by Error to turn the list of errors into a string.
Source Files