Also, the ./ prefix seems to happen both inside and outside of GOPATH, and independently of whether I'm building files or packages.

go tool compile f.go produces f.go:3:5: syntax error: unexpected EOF, expecting name or ( for me.
go build f.go or go.build produces ./f.go:3:5: syntax error: unexpected EOF, expecting name or (. This is for go version devel +99c30211b1 Fri Mar 9 23:11:59 2018 +0000 darwin/amd64 .

Finally, if there are line directives, the result changes again. For:

package p

//line foo:1
func

(with EOF after func), go tool compile f.go produces foo:1: syntax error: unexpected EOF, expecting name or (; go build f.go produces the same, and gofmt f.go produces foo:1: expected 'IDENT', found 'EOF'.

The file name is coming from cmd/go, not cmd/compile.

I think we need a clearer example of where an inconsistency happens. I don't think it is a problem if go/parser and cmd/go wind up with different file names, since they are being invoked differently.

@ianlancetaylor note that my point is about the inconsistency between go/parser based tools and the main cmd/... tools. For example, now that go test runs vet by default, an error with a filename might contain foo.go or ./foo.go, depending on whether the error comes from vet or from the compiler.

@mvdan I think what @ianlancetaylor is alluding to is that we need a clearer example of why it matters. The fact that one tool reports ./foo.go and the other one foo.fo doesn't necessarily mean one of them needs to change. Are there situations that cause actual problems because of this?

Ah, I see. It hasn't caused me any trouble other than me noticing and being slightly bothered by it :)

I actually do like the example of go test referring to the filename in different ways depending on whether it is reporting a compiler error or a vet error. I wasn't clear on that before. I think we should fix at least that case to be consistent, one way or another.

I think we need to start with just go vet consistency in test vs non test files to begin with.

output go vet on a .go file vs _test.go file

% go vet
vet: ./main.go:11:1: expected declaration, found k (and 1 more errors)

% go vet
main_test.go:11:1: expected declaration, found k
main_test.go:43:2: expected declaration, found err

end goal should be this in all cases, to make vet consistent with itself and other tools :)

./main.go:11:1: vet: expected declaration, found k