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author | Matthew Heon <matthew.heon@gmail.com> | 2017-11-01 11:24:59 -0400 |
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committer | Matthew Heon <matthew.heon@gmail.com> | 2017-11-01 11:24:59 -0400 |
commit | a031b83a09a8628435317a03f199cdc18b78262f (patch) | |
tree | bc017a96769ce6de33745b8b0b1304ccf38e9df0 /vendor/github.com/hashicorp/errwrap/README.md | |
parent | 2b74391cd5281f6fdf391ff8ad50fd1490f6bf89 (diff) | |
download | podman-a031b83a09a8628435317a03f199cdc18b78262f.tar.gz podman-a031b83a09a8628435317a03f199cdc18b78262f.tar.bz2 podman-a031b83a09a8628435317a03f199cdc18b78262f.zip |
Initial checkin from CRI-O repo
Signed-off-by: Matthew Heon <matthew.heon@gmail.com>
Diffstat (limited to 'vendor/github.com/hashicorp/errwrap/README.md')
-rw-r--r-- | vendor/github.com/hashicorp/errwrap/README.md | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/vendor/github.com/hashicorp/errwrap/README.md b/vendor/github.com/hashicorp/errwrap/README.md new file mode 100644 index 000000000..1c95f5978 --- /dev/null +++ b/vendor/github.com/hashicorp/errwrap/README.md @@ -0,0 +1,89 @@ +# errwrap + +`errwrap` is a package for Go that formalizes the pattern of wrapping errors +and checking if an error contains another error. + +There is a common pattern in Go of taking a returned `error` value and +then wrapping it (such as with `fmt.Errorf`) before returning it. The problem +with this pattern is that you completely lose the original `error` structure. + +Arguably the _correct_ approach is that you should make a custom structure +implementing the `error` interface, and have the original error as a field +on that structure, such [as this example](http://golang.org/pkg/os/#PathError). +This is a good approach, but you have to know the entire chain of possible +rewrapping that happens, when you might just care about one. + +`errwrap` formalizes this pattern (it doesn't matter what approach you use +above) by giving a single interface for wrapping errors, checking if a specific +error is wrapped, and extracting that error. + +## Installation and Docs + +Install using `go get github.com/hashicorp/errwrap`. + +Full documentation is available at +http://godoc.org/github.com/hashicorp/errwrap + +## Usage + +#### Basic Usage + +Below is a very basic example of its usage: + +```go +// A function that always returns an error, but wraps it, like a real +// function might. +func tryOpen() error { + _, err := os.Open("/i/dont/exist") + if err != nil { + return errwrap.Wrapf("Doesn't exist: {{err}}", err) + } + + return nil +} + +func main() { + err := tryOpen() + + // We can use the Contains helpers to check if an error contains + // another error. It is safe to do this with a nil error, or with + // an error that doesn't even use the errwrap package. + if errwrap.Contains(err, ErrNotExist) { + // Do something + } + if errwrap.ContainsType(err, new(os.PathError)) { + // Do something + } + + // Or we can use the associated `Get` functions to just extract + // a specific error. This would return nil if that specific error doesn't + // exist. + perr := errwrap.GetType(err, new(os.PathError)) +} +``` + +#### Custom Types + +If you're already making custom types that properly wrap errors, then +you can get all the functionality of `errwraps.Contains` and such by +implementing the `Wrapper` interface with just one function. Example: + +```go +type AppError { + Code ErrorCode + Err error +} + +func (e *AppError) WrappedErrors() []error { + return []error{e.Err} +} +``` + +Now this works: + +```go +err := &AppError{Err: fmt.Errorf("an error")} +if errwrap.ContainsType(err, fmt.Errorf("")) { + // This will work! +} +``` |