Retraction in go.mod should be allowed to retract versions of subdirectory go.mod files in the same git repo

[fishy]

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

$ go version
go version go1.17.2 linux/amd64

Does this issue reproduce with the latest release?

This is the latest release

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/fishy/.cache/go-build"
GOENV="/home/fishy/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/fishy/.gopath/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/fishy/.gopath"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/nix/store/vydvhfg076dfchm93hn96li2k1jqh04n-go-1.17.2/share/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/nix/store/vydvhfg076dfchm93hn96li2k1jqh04n-go-1.17.2/share/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.17.2"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/fishy/work/test-go-mod-retract/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-build3897776340=/tmp/go-build -gno-record-gcc-switches"

What did you do?

This is forked from the discussion of #34055 and is an issue currently affecting Apache Thrift.

I made a minimal reproducible example at https://github.com/fishy/test-go-mod-retract to demonstrate the issue, but the high level summary is:

1. The project made a mistake by adding go.mod to a subdirectory, without realizing the consequences of that.
2. The project realized that's a mistake, removed the go.mod in the subdirectory and added go.mod to the root directory instead.
3. The action in 2 doesn't fix the issue totally. the version with go.mod under the subdirectory will be recognized by go toolchain (and pkg.go.dev site) as the "latest" version, over whatever git semver tag you tagged at the project later (for example, if you go to https://pkg.go.dev/github.com/apache/thrift@v0.15.0/lib/go/thrift, it will tell you that it's not the "latest" version).
4. Even if you try to retract that version from root go.mod file, it won't work (as I demonstrated in the test-go-mod-retract repo).

What did you expect to see?

Either:

1. We are able to retract a version from a previous, subdirectory go.mod file, from the root go.mod file

or

2. Provide a way to retract the whole go.mod file (e.g. we can add the subdirectory go.mod saying "every previous version coming out of this go.mod file are retracted and this go.mod file should be ignored")

What did you see instead?

The consequences of the mistake of adding subdirectory go.mod file lasts forever with no way to fix completely.

[seankhliao]

1 seems infeasible, the module system doesn't operate on the concept of repos, and individual modules are independent.

2 is already possible possible by publishing a higher version which retracts all the versions before, up to and including the current version

[fishy]

Sorry @seankhliao I didn't explain myself well in my proposal 2.

My understanding is (please correct me if I'm wrong) that the current thing we have in 2, is that yes we can retract all previous versions of this module in the subdirectory/go.mod file, but by doing so we are adding subdirectory/go.mod again, making the current version available, and we are going back to dealing with all the consequences of having a subdirectory/go.mod again, which totally defeats the purpose (the purpose is to retract all versions under subdirectory/go.mod and make it to always use root go.mod going forward).

Thus, my proposal is to add something like (any of the following or some better names, I'm bad at names):

• retract *
• retract all
• retract module
• retract-module
• retract_module
• etc.

With the semantic of "retract all previous versions of this module, and also ignore the current version of this module and lookup the parent directory for go module instead".

Does that make sense?

[seankhliao]

Say you're currently have subdirectory/go.mod tagged with subdirectory/v0.15.0.

You can add a commit with subdirectory/go.mod with retract [v0.0.0-00000000000000-000000000000, v0.15.1], publish it by tagging subdirectory/v0.15.1 then remove afterwards. go should treat it as retracting all versions up to that point,

[fishy]

Thankns, @seankhliao! That worked.