mirror of
https://github.com/letic/terraform-provider-google.git
synced 2024-09-07 09:36:44 +00:00
92 lines
2.4 KiB
Markdown
92 lines
2.4 KiB
Markdown
# 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](https://github.com/hashicorp/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.
|
|
|
|
```go
|
|
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:
|
|
|
|
```go
|
|
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:
|
|
|
|
```go
|
|
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:
|
|
|
|
```go
|
|
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()
|
|
```
|