Generated protobuf and pb.go for batch/v1alpha1/Job does not compile

[zwx4d6]

Describe the bug

I'm trying to use the batch/Job as part of protobuf-based API and golang service. Different from k8s.io/api packages, this package does not provide pre-built protobuf nor generated pb.go files, so I have to generate them by myself. The following descriptions are tested on v1.12.2, but as of v1.13.0 the corresponding lines are not changed.

The generator is k8s.io/code-generator/cmd/go-to-protobuf@v0.32.0.

1. JobSpec.Plugins is typed as map[string][]string, whose value type []string cannot be directly translated to protobuf. repeated string is not a valid protobuf map value type, as specified in protocol buffers documentation. The generated type is map[string]string, so pb.go does not compile. K8s protobuf generator does have corresponding (old) issues like Cannot generate protobuf for map[string][]string, blocks authorization from being generated kubernetes/kubernetes#27259, and the mitigation is an extra layer of type definition type PluginArgs []string, like in Cannot generate protobuf for map[string][]string kubernetes/kubernetes#46024 (comment).
   Generated message piece:

// JobSpec describes how the job execution will look like and when it will actually run.
message JobSpec {
  //...

  // Specifies the plugin of job
  // Key is plugin name, value is the arguments of the plugin
  // +optional
  map<string, string> plugins = 6;

  // ...
}

Generated go code piece, commented by me:

			if m.Plugins == nil {
				m.Plugins = make(map[string]string) // type error here, m.Plugins is `map[string][]string`
			}
			var mapkey string
			var mapvalue string
// parsing byte buffer omitted
			m.Plugins[mapkey] = mapvalue

2. NetworkTopologySpec.HighestTierAllowed is typed as *int, but in the generated protobuf (thus pb.go) it is considered a int64, so go compiler fails to assign int64 to int. This might be easier to fix by explicitly assigning fixed width type int32 or int64.
   Generated message:

message NetworkTopologySpec {
  // Mode specifies the mode of the network topology constrain.
  // +kubebuilder:default=hard
  // +optional
  optional string mode = 1;

  // HighestTierAllowed specifies the highest tier that a job allowed to cross when scheduling.
  // +kubebuilder:default=1
  // +optional
  optional int64 highestTierAllowed = 2;
}

Generated go code piece, commented by me:

			var v int64 // here defines value
// parsing byte buffer omitted
			m.HighestTierAllowed = &v // type error here, m.HighestTierAllowed is `*int`

Proposed Fix

I'm not sure whether the changes are possible because they may be breaking.

1. Add type definition type PluginArgs []string with proper annotations and change type of JobSpec.Plugins to map[string]PluginArgs.
2. Change type of NetworkTopologySpec.HighestTierAllowed to int32 or int64.

19a20,21
>       "fmt"
> 
78c80
<       Plugins map[string][]string `json:"plugins,omitempty" protobuf:"bytes,6,opt,name=plugins"`
---
>       Plugins map[string]PluginArgs `json:"plugins,omitempty" protobuf:"bytes,6,opt,name=plugins"`
116a119,127
> // PluginArgs represents plugin argument list.
> // +protobuf.nullable=true
> // +protobuf.options.(gogoproto.goproto_stringer)=false
> type PluginArgs []string
> 
> func (a PluginArgs) String() string {
>       return fmt.Sprintf("%v", []string(a))
> }
> 
139c150
<       HighestTierAllowed *int `json:"highestTierAllowed,omitempty" protobuf:"bytes,2,opt,name=highestTierAllowed"`
---
>       HighestTierAllowed *int32 `json:"highestTierAllowed,omitempty" protobuf:"bytes,2,opt,name=highestTierAllowed"`

To Reproduce

Steps to reproduce the behavior:

1. Create a folder layout like K8s project, e.g. /code/staging/src/{k8s.io/api, k8s.io/apimachinery, volcano.sh/apis, github.com/gogo/protobuf} and copy corresponding source files. Absolute path is needed in later commands.

Though github.com/gogo/protobuf is archived, the removal from k8s proto generator is still in progress.

2. Install k8s.io/code-generator/cmd/go-to-protobuf and the plugin k8s.io/code-generator/cmd/go-to-protobuf/protoc-gen-gogo, and make sure protoc finds the plugin.
3. Inside the staging/src/volcano.sh/apis dir, run the generator: go-to-protobuf -v 5 --packages volcano.sh/apis/pkg/apis/bus/v1alpha1,volcano.sh/apis/pkg/apis/batch/v1alpha1 --apimachinery-packages -k8s.io/apimachinery/pkg/apis/meta/v1,-k8s.io/apimachinery/pkg/util/intstr,-k8s.io/apimachinery/pkg/api/resource,-k8s.io/apimachinery/pkg/runtime/schema,-k8s.io/apimachinery/pkg/runtime,-k8s.io/apimachinery/pkg/apis/meta/v1beta1,-k8s.io/apimachinery/pkg/apis/testapigroup/v1,-k8s.io/api/core/v1 --output-dir /code/staging/src --proto-import /code/staging/src --proto-import /code/staging/src/github.com/gogo/protobuf/protobuf. The leading - of k8s packages means their proto should not be generated (because they are already there).
4. Navigate to staging/src/volcano.sh/apis/pkg/apis/batch/v1alpha1, check generated.proto and generated.pb.go files, or just try to compile with go build:

❯ go build ./...
# volcano.sh/apis/pkg/apis/batch/v1alpha1
pkg/apis/batch/v1alpha1/generated.pb.go:767:13: invalid argument: arguments to copy dAtA[i:] (value of type []byte) and v (variable of type []string) have different element types byte and string
pkg/apis/batch/v1alpha1/generated.pb.go:2546:17: cannot use make(map[string]string) (value of type map[string]string) as map[string][]string value in assignment
pkg/apis/batch/v1alpha1/generated.pb.go:2641:24: cannot use mapvalue (variable of type string) as []string value in assignment
pkg/apis/batch/v1alpha1/generated.pb.go:3900:27: cannot use &v (value of type *int64) as *int value in assignment

Expected behavior

The generated protobuf aligns with CRD structs and generated go code compiles.