Lets say you have a simple function as so:
func create(path string) error {
if err := ioutil.WriteFile(path, []byte{}, 0666); err != nil {
return err
}
if err := os.Chmod(path, 0666); err != nil {
_ = os.Remove(path)
return err
}
return nil
}
I don't like ignoring the error out of Remove(). But I also don't want to swamp the error out of Chmod() and I don't want to leave the file since we didn't create() it successfully.
This is a simple example, and perhaps the function could be written differently to avoid this, but there are more complex situations that come up and this combining of errors I haven't seen mentioned in the golang community, so whats the idiom?
The solution would be to store the error from Remove in a separate variable, and combine them with fmt.Errorf:
if err := os.Chmod(path, 0666); err != nil {
if e2 := os.Remove(path); e2 != nil {
return fmt.Errorf("error changing permissions (%v); error deleting file (%v)", err, e2)
}
return err
}
You may have a look at my library for streamlined error handling and piping of function calls https://github.com/go-on/queue Example of usage:
import "github.com/go-on/queue/q"
func main() {
u := &User{}
err := q.Q(
ioutil.ReadAll, rq.Body, // read json (returns json and error)
)(
// q.V pipes the json from the previous function call
json.Unmarshal, q.V, u, // unmarshal json from above (returns error)
)(
u.Validate, // validate the user (returns error)
)(
u.Save, // save the user (returns error)
)(
ok, w, // send the "ok" message (returns no error)
).Run()
if err != nil {
switch err {
case *json.SyntaxError:
...
}
}
}