go vet incorrectly recognizes format verb in string

[skaldesh]

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

$ go version
go version go1.14.1 linux/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/skaldesh/.cache/go-build"
GOENV="/home/skaldesh/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOOS="linux"
GOPATH="/home/skaldesh/go"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build572355618=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I wrote a function that executes either fmt.Printf or fmt.Print, based on its arguments.
I am using it to generate go code

Sample: https://play.golang.org/p/Pb1JwPOmDLd

What did you expect to see?

No go vet error, as it lets my tests fail.

What did you see instead?

go vet error: write format %s reads arg #1, but call has 0 args

Additional info

It may be related to this old issue?

[ianlancetaylor]

I think it's asking quite a lot for vet to be able to disentangle this code. Normally a string is either a format or it isn't. It's a reasonable assumption for vet to make. In your case a string is sometimes a format string and sometimes isn't. If you want to use vet on your code, either use "%s" with a single argument, or use a separate function when you don't want to do formatting.

[skaldesh]

My intention was not to demand that go vet supports this. I was more surprised that I can not write this code and have my tests work at the same time...

[ianlancetaylor]

go test runs go vet by default. You can this with the -vet=off flag.