SA4017 false positive

[arashpayan]

Firstly, thank you for building such an incredible tool! It's saved me from many bugs. :-)

I recently encountered a false positive while working on some code that I've reduced to the smallest reproducible example I could and attached to this issue.

• The output of 'staticcheck -version'
  staticcheck 2020.2.3 (v0.1.3)

• The output of 'staticcheck -debug.version' (it is fine if this command fails)

staticcheck 2020.2.3 (v0.1.3)

Compiled with Go version: go1.16.2
Main module:
	honnef.co/go/tools@v0.1.3 (sum: h1:qTakTkI6ni6LFD5sBwwsdSO+AQqbSIxOauHTTQKZ/7o=)
Dependencies:
	github.com/BurntSushi/toml@v0.3.1 (sum: h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=)
	golang.org/x/mod@v0.3.0 (sum: h1:RM4zey1++hCTbCVQfnWeKs9/IEsaBLA8vTkd0WVtmH4=)
	golang.org/x/sys@v0.0.0-20210119212857-b64e53b001e4 (sum: h1:myAQVi0cGEoqQVR5POX+8RR2mrocKqNN1hmeMqhX27k=)
	golang.org/x/tools@v0.1.0 (sum: h1:po9/4sTYwZU9lPhi1tOrb4hCv3qrhiQ77LZfGa2OjwY=)
	golang.org/x/xerrors@v0.0.0-20200804184101-5ec99f83aff1 (sum: h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=)

• The output of 'go version'
  go version go1.16.2 linux/amd64

• The output of 'go env'

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/<REDACTED>/.cache/go-build"
GOENV="/home/<REDACTED>/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/<REDACTED>/gocode/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/<REDACTED>/gocode"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.2"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/<REDACTED>/scheck/go.mod"
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-build199834044=/tmp/go-build -gno-record-gcc-switches"

• Exactly which command you ran
  staticcheck ./...

• Output of the command and what's wrong with the output
  app/app.go:21:10: Errorf is a pure function but its return value is ignored (SA4017)
  The return value from fmt.Errorf is used as the return value of the function. It's definitely being used.

• Where we can read the code you're running staticcheck on
  I've attached a tiny project that reproduces the bug with the smallest example I could make. scheck.tar.gz

There seem to be 2 key elements to triggering the bug.

1. The method must not be in the main package.
2. If I remove the for loop at the end of the function, the error also disappears.

The example is based on a server that I'm writing, hence the non-terminating for loop.

In short, staticcheck has a problem with the following bit of code:

func Run() error {
	err := configEnvironment()
	if err != nil {
		return fmt.Errorf("failed to load config: %v", err)  // <-- FALSE POSITIVE HERE
	}
        // method continues

If I return err directly instead of wrapping it with fmt.Errorf() the error will also go away.

[dominikh]

Thanks for reducing the problem to a minimal example. I can reproduce the issue and am looking into it.

[dominikh]

This is fixed in master. I will make a new patch release containing the fix early next week.