x/vgo: do not add refs to non-module v2.0.0 during go.mod auto-creation

[fishy]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.10 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

GOARCH="amd64"
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"

What did you do?

The repo to reproduce this issue is https://github.com/fishy/gcsbucket (at time of reporting, HEAD is at 618d60fe84e06f5e695a7be52566b40d198191a5). It imports cloud.google.com/go/storage (and also github.com/fishy/fsdb, but that one doesn't have any other 3rd party dependencies).

Running vgo build the first time builds successfully, generating go.mod file:

module "github.com/fishy/gcsbucket"

require (
        "cloud.google.com/go" v0.0.0-20180119154837-767c40d6a2e0
        "github.com/fishy/fsdb" v0.0.0-20180217030800-5527ded01371
        "github.com/golang/protobuf" v1.0.0
        "github.com/googleapis/gax-go" v2.0.0
        "golang.org/x/net" v0.0.0-20180216171745-136a25c244d3
        "golang.org/x/oauth2" v0.0.0-20180207181906-543e37812f10
        "golang.org/x/text" v0.0.0-20180208041248-4e4a3210bb54
        "google.golang.org/api" v0.0.0-20180217000815-c7a403bb5fe1
        "google.golang.org/appengine" v1.0.0
        "google.golang.org/genproto" v0.0.0-20180206005123-2b5a72b8730b
        "google.golang.org/grpc" v1.10.0
)

Then running vgo build again will complain about:

vgo: errors parsing go.mod:
/Users/fishy/work/gopath/src/github.com/fishy/gcsbucket/go.mod:7: invalid module: github.com/googleapis/gax-go should be v1, not v2 (v2.0.0)

[fishy]

vgo version tested: 425260f20c6969ca9c30c7efe3c8019fddd3c416.

[AlexRouSg]

vgo does not allow depending on packages >v1 without a go.mod file

[fishy]

To clarify, running vgo build without go.mod file will generate the file automatically, with v2.0.0 for github.com/googleapis/gax-go. Running vgo build with go.mod file it generated before will throw that error and refuse to build.

[AlexRouSg]

Sorry I meant the dependency must have a go.mod file to use v2+
So you either have to get github.com/googleapis/gax-go to add a go.mod file or maybe try manually changing the version to v0.0.0-yyyymmddhhmmss-commit

[fishy]

In that case I think the proper fix should be that while generating go.mod file, use v0.0.0-yyyymmddhhmmss-commit instead of v2.0.0 when the target repository doesn't have go.mod file.

[AlexRouSg]

Yeah, but I think a new bug report on that is better. Unless you want to try and repurpose this issue by changing the title and description.

[fishy]

Title updated.

[rsc]

Yes, the problem is that the auto-converter for some reason decided to use v2.0.0 instead of a pseudo-commit.

[gopherbot]

Change https://golang.org/cl/107660 mentions this issue: cmd/go/internal/modfetch: fix conversion of legacy v2 versions