x/vgo: vgo unable to find go.mod file of package in tagged GitHub repo

[vladimiroff]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.10.2 linux/amd64 vgo:2018-02-20.1

Does this issue reproduce with the latest release?

Yes, even with just updated vgo (go get -u golang.org/x/vgo)

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

GOARCH="amd64"
GOBIN=""
GOCACHE="/home/kiril/.cache/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/kiril/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/lib/go"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
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-build218058509=/tmp/go-build -gno-record-gcc-switches"
VGOMODROOT=""

What did you do?

1. Forked github.com/pressly/goose in order to add go.mod file (there's a v2 version already)
2. In order to test my changes, in master branch I've renamed the package in master, created go.mod file with /v2 suffix of the module name and tagged the release as v2.3.2
3. Created a test project importing the new release:

mkdir $GOPATH/src/github.com/vladimiroff/foo
cd $GOPATH/src/github.com/vladimiroff/foo

4. Created dummy foo.go just to import forked version of goose:

package foo // import "github.com/vladimiroff/foo"
import goose "github.com/vladimiroff/goose/v2"

var MaxVersion = goose.MaxVersion

func Foo() goose.SQLDialect {
        return goose.GetDialect()
}

5. Created go.mod file as well:

module github.com/vladimiroff/foo

require github.com/vladimiroff/goose/v2 v2.3.2

What did you expect to see?

vgo build to succeed.

What did you see instead?

--> vgo build
vgo: finding github.com/vladimiroff/goose/v2 v2.3.2
vgo: github.com/vladimiroff/goose/v2 v2.3.2: missing go.mod
vgo: finding github.com/vladimiroff/goose/v2 v2.3.2
vgo: github.com/vladimiroff/goose/v2 v2.3.2: missing go.mod

There's obviously a go.mod file in there: https://github.com/vladimiroff/goose/blob/v2.3.2/go.mod

vgo build succeeds only after replacing github.com/vladimiroff/goose/v2 with local version of the package in go.mod:

module github.com/vladimiroff/foo

replace github.com/vladimiroff/goose/v2 v2.3.2 => ../goose
require github.com/vladimiroff/goose/v2 v2.3.2

[rogpeppe]

I'll add to this. When I tried a "vgo get -u" with that goose repo, I saw this panic:

% vgo get -u
vgo: finding gopkg.in/check.v1 latest
vgo: finding gopkg.in/yaml.v2 latest
vgo: finding gopkg.in/check.v1 latest
vgo: resolving import "github.com/vladimiroff/goose/v2"
vgo: finding github.com/vladimiroff/goose (latest)
vgo: adding github.com/vladimiroff/goose v0.0.0-20180522081621-7b08ab39b54e
vgo: finding gopkg.in/check.v1 latest
vgo: finding gopkg.in/yaml.v2 latest
vgo: finding github.com/vladimiroff/goose latest
vgo: finding gopkg.in/check.v1 latest
vgo: finding github.com/vladimiroff/goose v0.0.0-20180522081621-7b08ab39b54e
panic: downloaded "github.com/vladimiroff/goose" and got module "github.com/vladimiroff/goose/v2"

goroutine 1 [running]:
golang.org/x/vgo/vendor/cmd/go/internal/mvs.UpgradeAll(0xc0001f0200, 0x1b, 0x0, 0x0, 0x98c0e0, 0xc00022aa60, 0xc0000aac00, 0x3, 0x4, 0x0, ...)
	/home/rog/src/go/src/golang.org/x/vgo/vendor/cmd/go/internal/mvs/mvs.go:174 +0x62c
golang.org/x/vgo/vendor/cmd/go/internal/vgo.iterate(0xc0001d9a78)
	/home/rog/src/go/src/golang.org/x/vgo/vendor/cmd/go/internal/vgo/load.go:140 +0x210
golang.org/x/vgo/vendor/cmd/go/internal/vgo.importPaths(0xc0002d4280, 0x1, 0x1, 0xd0, 0x8d2760, 0x30)
	/home/rog/src/go/src/golang.org/x/vgo/vendor/cmd/go/internal/vgo/load.go:83 +0xde
golang.org/x/vgo/vendor/cmd/go/internal/vgo.ImportPaths(0xc0001d9c50, 0x1, 0x1, 0x0, 0x8b5148, 0x30)
	/home/rog/src/go/src/golang.org/x/vgo/vendor/cmd/go/internal/vgo/load.go:71 +0x58
golang.org/x/vgo/vendor/cmd/go/internal/vgo.runGet(0xbb5be0, 0xc00001e0b0, 0x0, 0x0)
	/home/rog/src/go/src/golang.org/x/vgo/vendor/cmd/go/internal/vgo/get.go:54 +0xebb
golang.org/x/vgo/vendor/cmd/go.Main()
	/home/rog/src/go/src/golang.org/x/vgo/vendor/cmd/go/main.go:155 +0x7a9
main.main()
	/home/rog/src/go/src/golang.org/x/vgo/main.go:31 +0x20

When I tried again from scratch, I couldn't reproduce this, but perhaps the panic is enough in itself.

[kardianos]

There is an issue resolving the module path from the go.mod file in vgo/vendor/cmd/go/internal/modfetch/coderepo.go Line 246 in func modPath. We should add some unit tests to this package to test this function and make it more robust.

CL coming up.

[gopherbot]

Change https://golang.org/cl/114005 mentions this issue: cmd/go/internal/modfetch: use modfile when finding module path

[kardianos]

@rogpeppe I was unable to reproduce your panic either :/

@vladimiroff The attached CL fixes the issue you experienced. Feel free to confirm.

[kardianos]

Change https://golang.org/cl/114058 also fixes this issue. I just saw it when I pushed to Gerrit and saw the merge conflicts. I think parts of both CLs could be useful to get in.

[AlexRouSg]

@kardianos A reliable way to get the panic is to have a empty (other than the module declaration) go.mod file and vgo build. (where the package imports github.com/vladimiroff/goose/v2)

[kardianos]

Huh. It doesn't do that anymore with the linked CL.

[AlexRouSg]

ohh nvm then, didn't tried the CL

[bcmills]

This seems to be fixed at head. (Following your steps to reproduce, vgo build succeeded for me.)

Please reopen if you're still able to reproduce the problem.