cmd/go: go mod init in GOPATH can create invalid module path

[perillo]

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

$ go version
go version go1.16.4 linux/amd64

Does this issue reproduce with the latest release?

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

go env Output

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN="/home/manlio/.local/bin"
GOCACHE="/home/manlio/.cache/go-build"
GOENV="/home/manlio/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE="*.local"
GOMODCACHE="/home/manlio/.local/lib/go/pkg/mod"
GONOPROXY=""
GONOSUMDB="*.local"
GOOS="linux"
GOPATH="/home/manlio/.local/lib/go:/home/manlio/src/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.4"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
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-build3071205222=/tmp/go-build -gno-record-gcc-switches"
GOROOT/bin/go version: go version go1.16.4 linux/amd64
GOROOT/bin/go tool compile -V: compile version go1.16.4
uname -sr: Linux 5.11.16-arch1-1
/usr/lib/libc.so.6: GNU C Library (GNU libc) release release version 2.33.
gdb --version: GNU gdb (GDB) 10.1

What did you do?

Assuming $GOPATH is ~/go:

mkdir "~/go/src/test.localhost/space in dir"
cd "~/go/src/test.localhost/space in dir"
go mod init

What did you expect to see?

An error reported by go mod init, since the computed module path is incorrect.

What did you see instead?

$ cat go.mod
module "test.localhost/space in dir"

go 1.16

The issue is probably the same as the one in #45025, however in this case go mod is free to don't use the auto generated module path.

[heschi]

cc @bcmills @jayconrod @matloob

[jayconrod]

CL 288712 will probably fix this.

[perillo]

@jayconrod, you are right, thanks.

Looking at the source code, findModulePath returns the error bad module path inferred from directory in GOPATH in case of invalid module path. It calls checkModulePathLax.

I'm not closing this issue because https://go-review.googlesource.com/c/go/+/288712 don't have tests for this use case.

[perillo]

Looking at cmd/go/testdata/script/mod_init*, it seems there are no tests to cover the findModulePath function.

[gopherbot]

Change https://golang.org/cl/320310 mentions this issue: cmd/go: align checks of module path when creating go.mod file

[gopherbot]

Change https://golang.org/cl/288712 mentions this issue: cmd/go: make mod init disallow invalid major version suffixes