cmd/go: 'go mod vendor' should not remove existing non-Go content from the vendor subdirectory

[reitzig]

Tl;dr: Go is not the only tool I use in my project; I expect it share vendor peacefully.

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

$ go version
go version go1.15.8 linux/amd64

(latest at the time of this writing)

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/raphael/.cache/go-build"
GOENV="/home/raphael/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/raphael/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/raphael/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/raphael/Code/tools/container-do/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-build500284300=/tmp/go-build -gno-record-gcc-switches"

What did you do?

# Gemfile
source "https://rubygems.org"

group :test do
  gem 'cucumber', '~> 5'
  gem 'rspec', '~> 3'
end

# go.mod
module github.com/reitzig/container-do

go 1.15

require (
	github.com/pelletier/go-toml v1.8.1
	go.uber.org/zap v1.16.0
)

bundle2.7 config set --local path 'vendor/bundle'
bundle2.7 install
go mod vendor

What did you expect to see?

Ruby gems and Go modules "installed" in vendor.

What did you see instead?

Only Go modules in vendor.

Workaround

Bundler leaves Go modules alone, so re-running bundle install after go mod vendor creates the desired state.

[mvdan]

This seems like a duplicate of #26366.

[reitzig]

Very old and unsolved, but yes, essentially the same issue. Don't know if, after all this time, it refers to the same implementation anymore.

No, that issue is concerned with impact on directories outside of vendor, while my use case is with different tools storing data inside vendor.

[fgergo]

@bcmills @seankhliao I'm not sure current issue title is precise: "cmd/go: 'go mod vendor' should not remove existing non-Go content from the vendor subdirectory"
"go mod vendor" removes everything when it comes to that conclusion without any warning. It removes both go code and other files as well like I described in #45355 .
I believe a title like
"cmd/go: 'go mod vendor' should not remove existing content from the vendor subdirectory without any warning"
describes the situation more precisely.

[reitzig]

To be clear: my intent was for go mod to leave all files it isn't responsible for in peace. A warning would be good either way, but I don't want it to remove the Ruby files at all! It can do whatever it wants with Go files for all I care since that's its job.

If it insists on completely owning that directory, it needs to be configurable.