net: DefaultResolver.LookupIP returns no error and nil IP address for empty string

[davidbrink]

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

$ go version
go version go1.17 darwin/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="/Users/dbrink/Library/Caches/go-build"
GOENV="/Users/dbrink/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/dbrink/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/dbrink/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.17"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/dbrink/Desktop/sps/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 -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/gb/vk5wy1jd4msc49d1vpdwf_j80015jz/T/go-build1545005800=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

https://go.dev/play/p/o1nR6WBsGQT

What did you expect to see?

An error when looking up the empty hostname.

What did you see instead?

No error and a nil IP address.

[ianwoolf]

DefaultResolver.LookupIP returns {nil}, nil when host is "". This is because r.internetAddrList returns the inetaddr(IPAddr{}):
https://cs.opensource.google/go/go/+/master:src/net/ipsock.go;l=284

It seems that return inetaddr(IPAddr{}) is expected. But I think the return of Resolver.LookupIP should be {}, nil, not {nil}, nil. Or return an error like net.LookupIP does.

[gopherbot]

Change https://go.dev/cl/419734 mentions this issue: net: fix the return of Resolver.LookupIP when the host is empty

[ianwoolf]

i send a wip cl and want help. I'm wondering if it's more appropriate to return an error, or just return an empty slice.

please feel free to review

[ianlancetaylor]

Looking up an empty host name should probably return some sort of error.

[ianwoolf]

Change https://go.dev/cl/419734 mentions this issue: net: fix the return of Resolver.LookupIP when the host is empty

pleas feel free to review