cmd/go: 'go mod init' should reject module paths that are not valid import paths

[nemith]

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

$ go version
go version go1.16.2 linux/amd64

Does this issue reproduce with the latest release?

Tested on Go 1.16.2 and on tip using gotip

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/bbennett/.cache/go-build"
GOENV="/home/bbennett/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/bbennett/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/bbennett/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/opt/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/opt/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.2"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/bbennett/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-build45415822=/tmp/go-build -gno-record-gcc-switches"

What did you do?

$ go mod init "bad module"
$ cat go.mod
module "bad module"

go 1.16

What did you expect to see?

An error about the import path not being correct due to the space and not have the go.mod file created

What did you see instead?

go: creating new go.mod: module bad mod
go: to add module requirements and sums:
	go mod tidy

Also once trying to use the module then I get an error about the module name.

[bbennett@bbennett-fedora-PC1RSH91 tmp]$ go run .
malformed import path "bad mod": invalid char ' '

[cherrymui]

cc @bcmills @jayconrod @matloob

[bcmills]

(See also #36774, #44052, #31549.)

[bcmills]

We can't reject module paths that fail module.CheckPath, because they may be needed for users to migrate from GOPATH mode to modules (and can be used in conjunction with replace directives even if they can't be fetched from a proxy). However, we certainly should reject module paths that fail module.CheckImportPath.

I thought we had fixed this in CL 211597, but I guess we missed something there. 😞

CC @matloob @jayconrod

[nemith]

This may be as simple as adding ' '(space) to the one of the reject lists (it's really not a shell character or a fs character though). I wonder what other character may need to be blocked.

[oiooj]

Yes, this issue fixed in CL 211597 .

  $WORK/gopath/src/mod
  > go mod init "bad module"
  [stderr]
  go mod init: too many arguments
  [exit status 1]
  FAIL: testdata/script/mod_invalid_importpath.txt:5: unexpected command failure

[bcmills]

@oiooj, it's nice that go mod init now correctly rejects this path, but IMO too many arguments is a pretty confusing error message. I'd like to leave this issue open to at least improve that. 🙂

[jayconrod]

go mod init currently does not reject spaces.

$ go mod init "bad module"
go: creating new go.mod: module bad module
$ cat go.mod
module "bad module"

go 1.16

(I think testscript interprets " literally; that would explain the too many arguments error, which I agree should be clarified).

Now that we have separate validation for import paths, perhaps we should call module.CheckImportPath on top of the existing restrictions? It shouldn't be possible to create a module with go mod init if we can't import its packages.

[gopherbot]

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

[iwdgo]

With the suggested CL, space in a module name is rejected as expected.

>goissue mod init "bad example"
go: malformed import path "bad example": invalid char ' '