kubebuilder: No GOPATH environment variable breaks code generators

Problem

If one uses the default gopath at $HOME/go, and therefore does not set a GOPATH environment variable, the deepcopy-gen will save its output files into the wrong destination path.

This is the output if one just tries to follow the quickstart without a defined GOPATH environment variable:

go generate ./pkg/... ./cmd/...
go fmt ./pkg/... ./cmd/...
go vet ./pkg/... ./cmd/...
# ships/pkg/apis/ships/pkg/apis/ships/v1beta1
pkg/apis/ships/pkg/apis/ships/v1beta1/zz_generated.deepcopy.go:27:11: undefined: Sloop
make: *** [Makefile:38: vet] Error 2

As one can see the output gets saved to pkg/apis/ships/pkg/apis/ships, so the relative output base is wrong.

The deepcopygen command line is defined in the pkg/apis/apis.go like this:

// Generate deepcopy for apis
//go:generate go run ../../vendor/k8s.io/code-generator/cmd/deepcopy-gen/main.go -O zz_generated.deepcopy -i ./... -h ../../hack/boilerplate.go.txt

It is not setting the output base on the command line, which works like this according to the help:

-o, --output-base string               Output base; defaults to $GOPATH/src/ or ./ if $GOPATH is not set. (default "./")

As there is no GOPATH set, the default is the current working directory, and this is why there is the duplicate pkg/apis/ships path in the destination.

Workaround:

Simply set your GOPATH environment variable like:

export GOPATH="$HOME/go"

Possible Solutions:

1. simply document the workaround that the GOPATH environment variable must be set
2. maybe be specific in the go:generate command line and add a -o
3. change the default behaviour for deepcopy-gen ? I don’t think this is a good idea though, it’s pretty clear how it should work