author | Mikael Berthe <mikael@lilotux.net> |
Sun, 13 Jan 2019 13:41:09 +0100 | |
changeset 246 | 0998f404dd31 |
parent 242 | 2a9ec03fe5a1 |
child 251 | 1c52a0eeb952 |
permissions | -rw-r--r-- |
246 | 1 |
# errors [![Travis-CI](https://travis-ci.org/pkg/errors.svg)](https://travis-ci.org/pkg/errors) [![AppVeyor](https://ci.appveyor.com/api/projects/status/b98mptawhudj53ep/branch/master?svg=true)](https://ci.appveyor.com/project/davecheney/errors/branch/master) [![GoDoc](https://godoc.org/github.com/pkg/errors?status.svg)](http://godoc.org/github.com/pkg/errors) [![Report card](https://goreportcard.com/badge/github.com/pkg/errors)](https://goreportcard.com/report/github.com/pkg/errors) [![Sourcegraph](https://sourcegraph.com/github.com/pkg/errors/-/badge.svg)](https://sourcegraph.com/github.com/pkg/errors?badge) |
242
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
2 |
|
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
3 |
Package errors provides simple error handling primitives. |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
4 |
|
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
5 |
`go get github.com/pkg/errors` |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
6 |
|
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
7 |
The traditional error handling idiom in Go is roughly akin to |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
8 |
```go |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
9 |
if err != nil { |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
10 |
return err |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
11 |
} |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
12 |
``` |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
13 |
which applied recursively up the call stack results in error reports without context or debugging information. The errors package allows programmers to add context to the failure path in their code in a way that does not destroy the original value of the error. |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
14 |
|
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
15 |
## Adding context to an error |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
16 |
|
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
17 |
The errors.Wrap function returns a new error that adds context to the original error. For example |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
18 |
```go |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
19 |
_, err := ioutil.ReadAll(r) |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
20 |
if err != nil { |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
21 |
return errors.Wrap(err, "read failed") |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
22 |
} |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
23 |
``` |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
24 |
## Retrieving the cause of an error |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
25 |
|
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
26 |
Using `errors.Wrap` constructs a stack of errors, adding context to the preceding error. Depending on the nature of the error it may be necessary to reverse the operation of errors.Wrap to retrieve the original error for inspection. Any error value which implements this interface can be inspected by `errors.Cause`. |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
27 |
```go |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
28 |
type causer interface { |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
29 |
Cause() error |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
30 |
} |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
31 |
``` |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
32 |
`errors.Cause` will recursively retrieve the topmost error which does not implement `causer`, which is assumed to be the original cause. For example: |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
33 |
```go |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
34 |
switch err := errors.Cause(err).(type) { |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
35 |
case *MyError: |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
36 |
// handle specifically |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
37 |
default: |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
38 |
// unknown error |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
39 |
} |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
40 |
``` |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
41 |
|
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
42 |
[Read the package documentation for more information](https://godoc.org/github.com/pkg/errors). |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
43 |
|
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
44 |
## Contributing |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
45 |
|
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
46 |
We welcome pull requests, bug fixes and issue reports. With that said, the bar for adding new symbols to this package is intentionally set high. |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
47 |
|
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
48 |
Before proposing a change, please discuss your change by raising an issue. |
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
49 |
|
246 | 50 |
## License |
242
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
51 |
|
2a9ec03fe5a1
Use vendoring for backward compatibility
Mikael Berthe <mikael@lilotux.net>
parents:
diff
changeset
|
52 |
BSD-2-Clause |