vet: fmt.Errorf("ordinary string") should be replaced by errors.New("ordinary string")

[kevinburke]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

1.7.1

What operating system and processor architecture are you using (go env)?

All

What did you do?

Vet this program: https://play.golang.org/p/krp8cxL_Lv

package main

import "fmt"

func main() {
    err := fmt.Errorf("ordinary error")
    fmt.Printf("%#v\n", err)
}

What did you expect to see?

fmt.Errorf("an ordinary string") - with no formatting arguments - should be replaced by errors.New("an ordinary string"), to avoid the overhead of calling errors.New(Sprintf(...)).

What did you see instead?

No warning.

I'm happy to try to provide a patch here, if this is of interest.

[minux]

I'm not sure this is worth a vet check. For packages that already imports fmt, there is nothing to gain from using errors.New instead of fmt.Errorf (except slight performance gain, but that shouldn't matter). benchmark: https://play.golang.org/p/gXzQC2Ux4J

[dsnet]

vet is intended to check issues of correctness. The difference between using fmt.Errorf or errors.New here is clearly one of style since they are semantically equivalent. This should be an issue to file at golang/lint, which is intended to check issues of style. I just checked and it doesn't seem like golint complains about this case.

I'm going to close this, but feel free to open the issue on the lint tracker.

[minux]

For the reason I've given, I don't even think it's appropriate for golint to complain about: it's not a mistake if the package is already using the fmt package.

[jimmyfrasche]

Perhaps you could try https://github.com/dominikh/go-simple

[dominikh]

It's probably not appropriate for gosimple, either, for the reason minux has given. One could of course check if fmt is being used for anything else already, but I don't think the slight benefit is worth the added complexity.

[jimmyfrasche]

Well thought I'd mention it as it was the most likely place it would find a home that I know of.

Personally I'd consider it a simplification even if it meant importing errors and fmt. A Printf/Errorf/Anythingf with just a string looks wrong.

Understandable if it's out of scope, though.

[kevinburke]

OK