mirror of
https://github.com/imjasonh/client-go2
synced 2026-07-08 17:16:47 +00:00
trying to make the client simpler; doesn't work :(
This commit is contained in:
Jason Hall
parent
f6db51af0f
commit
59f526eccf
3 changed files with 102 additions and 102 deletions
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@ -1,8 +1,8 @@
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# Experimenting with `go-client` and Go generics
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This is an experimental type-parameter-aware client that wraps [`k8s.io/client-go/dynamic`](https://pkg.go.dev/k8s.io/client-go/dynamic).
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This is an experimental type-parameter-aware client that wraps [`k8s.io/client-go/dynamic`](https://pkg.go.dev/k8s.io/client-go/dynamic) _(...for now)_.
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Until Go 1.18 is released, use [`gotip`](https://pkg.go.dev/golang.org/dl/gotip)
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Until Go 1.18 is released, use [`gotip`](https://pkg.go.dev/golang.org/dl/gotip).
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Assuming you've got a working kubeconfig (does `kubectl get pods` work?), you can run this code:
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83
generic/client.go
Normal file
83
generic/client.go
Normal file
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@ -0,0 +1,83 @@
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package generic
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import (
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"bytes"
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"context"
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"encoding/json"
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"strings"
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"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
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"k8s.io/apimachinery/pkg/runtime/schema"
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"k8s.io/client-go/dynamic"
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"k8s.io/client-go/rest"
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metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
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)
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type obj interface {
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GetObjectKind() schema.ObjectKind
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}
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func NewClient[T obj](config *rest.Config) client[T] {
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return client[T] {
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dyn: dynamic.NewForConfigOrDie(config),
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}
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}
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type client[T obj] struct {
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dyn dynamic.Interface // TODO: don't depend on dynamic client
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}
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// gvr translates the T to a GVR, via GVK
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// GVK->GVR translation is a terrible hack; we need something better.
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func (c client[T]) gvr() schema.GroupVersionResource {
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// BOOM!
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// This panics because T is a nil *corev1.Pod; the runtime.Object interface is only satisfied by *corev1.Pod, not the instantiable corev1.Pod.
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// https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md#pointer-method-example
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var t T
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gvk := t.GetObjectKind().GroupVersionKind()
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return schema.GroupVersionResource{
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Group: gvk.Group,
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Version: gvk.Version,
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Resource: strings.ToLower(gvk.Kind) + "s", // HACK
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}
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}
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func (c client[T]) List(ctx context.Context, namespace string) ([]T, error) {
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ul, err := c.dyn.Resource(c.gvr()).Namespace(namespace).List(ctx, metav1.ListOptions{})
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if err != nil {
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return nil, err
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}
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var out []T
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for _, u := range ul.Items {
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var t T
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var buf bytes.Buffer
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if err := json.NewEncoder(&buf).Encode(u.Object); err != nil { return nil, err }
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if err := json.NewDecoder(&buf).Decode(t); err != nil { return nil, err }
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out = append(out, t)
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}
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return out, nil
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}
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func (c client[T]) Get(ctx context.Context, namespace, name string) (T, error) {
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var t T
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u, err := c.dyn.Resource(c.gvr()).Namespace(namespace).Get(ctx, name, metav1.GetOptions{})
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if err != nil {
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return t, err
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}
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var buf bytes.Buffer
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if err := json.NewEncoder(&buf).Encode(u.Object); err != nil { return t, err }
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if err := json.NewDecoder(&buf).Decode(t); err != nil { return t, err }
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return t, nil
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}
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func (c client[T]) Create(ctx context.Context, namespace string, t T) error {
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m := map[string]interface{}{}
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var buf bytes.Buffer
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if err := json.NewEncoder(&buf).Encode(t); err != nil { return err }
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if err := json.NewDecoder(&buf).Decode(&m); err != nil { return err }
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u := &unstructured.Unstructured{Object:m}
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_, err := c.dyn.Resource(c.gvr()).Namespace(namespace).Create(ctx, u, metav1.CreateOptions{})
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return err
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}
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117
main.go
117
main.go
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@ -1,22 +1,22 @@
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package main
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import (
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"bytes"
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"encoding/json"
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"context"
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"encoding/json"
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"log"
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"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
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"k8s.io/apimachinery/pkg/runtime"
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"k8s.io/apimachinery/pkg/runtime/schema"
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"k8s.io/client-go/dynamic"
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"k8s.io/client-go/rest"
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"k8s.io/client-go/tools/clientcmd"
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"github.com/imjasonh/client-go2/generic"
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corev1 "k8s.io/api/core/v1"
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metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
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"k8s.io/client-go/tools/clientcmd"
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)
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func main() {
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// This is load bearing...
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// Without this, while the client is in generic/, I get a mysterious compiler error:
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// "internal compiler error: missing import reader for json.NewEncoder"
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_ = json.NewEncoder(nil)
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ctx := context.Background()
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config, err := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(clientcmd.NewDefaultClientConfigLoadingRules(), &clientcmd.ConfigOverrides{}).ClientConfig()
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if err != nil {
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@ -24,16 +24,18 @@ func main() {
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}
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// List pods in kube-system.
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pods, err := NewClient[pod](config).List(ctx, "kube-system")
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if err != nil { log.Fatal("listing pods:", err) }
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pods, err := generic.NewClient[*corev1.Pod](config).List(ctx, "kube-system")
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if err != nil {
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log.Fatal("listing pods:", err)
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}
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log.Println("PODS")
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for _, p := range pods {
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log.Println("-", p.Name)
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}
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// Create a ConfigMap, then list ConfigMaps.
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cmc := NewClient[cm](config)
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if err := cmc.Create(ctx, "kube-system",cm{
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cmc := generic.NewClient[*corev1.ConfigMap](config)
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if err := cmc.Create(ctx, "kube-system", &corev1.ConfigMap{
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ObjectMeta: metav1.ObjectMeta{
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GenerateName: "foo-",
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},
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@ -44,96 +46,11 @@ func main() {
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log.Fatal("creating configmap:", err)
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}
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cms, err := cmc.List(ctx, "kube-system")
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if err != nil { log.Fatal("listing configmaps:", err) }
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if err != nil {
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log.Fatal("listing configmaps:", err)
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}
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log.Println("CONFIGMAPS")
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for _, cm := range cms {
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log.Println("-", cm.Name)
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}
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}
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func NewClient[T obj](config *rest.Config) client[T] {
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return client[T] {
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dyn: dynamic.NewForConfigOrDie(config),
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}
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}
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type client[T obj] struct {
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dyn dynamic.Interface
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}
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func (c client[T]) List(ctx context.Context, namespace string) ([]T, error) {
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var t T
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ul, err := c.dyn.Resource(t.GVR()).Namespace(namespace).List(ctx, metav1.ListOptions{})
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if err != nil {
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return nil, err
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}
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var out []T
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for _, u := range ul.Items {
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var t T
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var buf bytes.Buffer
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if err := json.NewEncoder(&buf).Encode(u.Object); err != nil { return nil, err }
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if err := json.NewDecoder(&buf).Decode(&t); err != nil { return nil, err }
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out = append(out, t)
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}
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return out, nil
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}
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func (c client[T]) Get(ctx context.Context, namespace, name string) (*T, error) {
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var t T
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u, err := c.dyn.Resource(t.GVR()).Namespace(namespace).Get(ctx, name, metav1.GetOptions{})
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if err != nil {
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return nil, err
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}
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var buf bytes.Buffer
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if err := json.NewEncoder(&buf).Encode(u.Object); err != nil { return nil, err }
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if err := json.NewDecoder(&buf).Decode(&t); err != nil { return nil, err }
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return &t, nil
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}
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func (c client[T]) Create(ctx context.Context, namespace string, t T) error {
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m := map[string]interface{}{}
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var buf bytes.Buffer
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if err := json.NewEncoder(&buf).Encode(t); err != nil { return err }
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if err := json.NewDecoder(&buf).Decode(&m); err != nil { return err }
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u := &unstructured.Unstructured{Object:m}
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_, err := c.dyn.Resource(t.GVR()).Namespace(namespace).Create(ctx, u, metav1.CreateOptions{})
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return err
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}
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// THESE ARE HACKS
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//
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// Ideally, the Pod type (or any runtime.Object) would be able to give us its
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// GVR directly, then the obj interface / type constraint would just be
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// runtime.Object.
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//
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// Since it can't, we have to wrap runtime.Object and provide these per-type.
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// This would be really nice to fix.
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type pod corev1.Pod
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func (pod pod) GetObjectKind() schema.ObjectKind { return pod.GetObjectKind() }
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func (pod pod) DeepCopyObject() runtime.Object { return pod.DeepCopyObject() }
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func (pod) GVR() schema.GroupVersionResource {
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return schema.GroupVersionResource{
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Group: "",
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Version: "v1",
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Resource: "pods",
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}
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}
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type cm corev1.ConfigMap
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func (cm cm) GetObjectKind() schema.ObjectKind { return cm.GetObjectKind() }
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func (cm cm) DeepCopyObject() runtime.Object { return cm.DeepCopyObject() }
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func (cm) GVR() schema.GroupVersionResource {
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return schema.GroupVersionResource{
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Group: "",
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Version: "v1",
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Resource: "configmaps",
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}
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}
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type obj interface {
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runtime.Object
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GVR() schema.GroupVersionResource
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}
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