x/tools/go/packages: cannot load "cmd" from within a module

[mvdan]

$ go version
go version devel +9d23975d89 Wed Jan 23 23:13:03 2019 +0000 linux/amd64
$ git describe --always
6466e726
$ go install ./gopackages
$ gopackages cmd >/dev/null; echo $?
0
$ mkdir /tmp/tempmodule
$ cd /tmp/tempmodule
$ go mod init tempmodule
go: creating new go.mod: module tempmodule
$ gopackages cmd >/dev/null; echo $?
gopackages: go list repeated package github.com/google/pprof/internal/driver with different values
2

This seems pretty serious - I'm having trouble using a linter that I wrote as it's now running into these errors. Perhaps related to #29826, but in this case the packages don't seem to be identical, as DeepEqual returns false.

/cc @matloob @ianthehat

[mvdan]

Seems like the issue is that it's loading the vendored packages as modules:

$ cat go.mod
module tempmodule

go 1.12

require (
        github.com/google/pprof v0.0.0-20190109223431-e84dfd68c163 // indirect
        github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6 // indirect
        golang.org/x/arch v0.0.0-20181203225421-5a4828bb7045 // indirect
        golang.org/x/crypto v0.0.0-20190123085648-057139ce5d2b // indirect
        golang.org/x/sys v0.0.0-20190124100055-b90733256f2e // indirect
        golang.org/x/tools v0.0.0-20190124004107-78ee07aa9465 // indirect
)

I'm starting to wonder if this is supposed to be broken. Still, I presume there's something to fix; the error is confusing.

Edit: as expected, GO111MODULE=off gopackages cmd always works. I'll be using this as a workaround for now.

[bcmills]

Dup of #26924, or at least closely related.

[mvdan]

Perhaps. The errors we end up with seem different, so I'm not sure if we should close this issue as a duplicate.

[bcmills]

Seems to be fixed at head.

~/src/golang.org/x/tools/go/packages$ go version
go version devel +49e7c7672d Mon Sep 16 11:56:15 2019 +0000 linux/amd64
~/src/golang.org/x/tools/go/packages$ go install ./gopackages
~/src/golang.org/x/tools/go/packages$ gopackages cmd >/dev/null; echo $?
0
~/src/golang.org/x/tools/go/packages$ mkdir /tmp/tempmodule
~/src/golang.org/x/tools/go/packages$ cd /tmp/tempmodule
/tmp/tempmodule$ go mod init tempmodule
go: creating new go.mod: module tempmodule
/tmp/tempmodule$ gopackages cmd >/dev/null; echo $?
0