Merge pull request #1231 from DirectXMan12/docs/client-object-godoc

📖 Improve docs for client.Object

pkg/client/object.go

@@ -21,15 +21,56 @@ import (
 	"k8s.io/apimachinery/pkg/runtime"
 )
 
-// Object is a Kubernetes object, allows functions to work indistinctly with any resource that
-// implements both Object interfaces.
+// Object is a Kubernetes object, allows functions to work indistinctly with
+// any resource that implements both Object interfaces.
+//
+// Semantically, these are objects which are both serializable (runtime.Object)
+// and identifiable (metav1.Object) -- think any object which you could write
+// as YAML or JSON, and then `kubectl create`.
+//
+// Code-wise, this means that any object which embeds both ObjectMeta (which
+// provides metav1.Object) and TypeMeta (which provides half of runtime.Object)
+// and has a `DeepCopyObject` implementation (the other half of runtime.Object)
+// will implement this by default.
+//
+// For example, nearly all the built-in types are Objects, as well as all
+// KubeBuilder-generated CRDs (unless you do something real funky to them).
+//
+// By and large, most things that implement runtime.Object also implement
+// Object -- it's very rare to have *just* a runtime.Object implementation (the
+// cases tend to be funky built-in types like Webhook payloads that don't have
+// a `metadata` field).
+//
+// Notice that XYZList types are distinct: they implement ObjectList instead.
 type Object interface {
 	metav1.Object
 	runtime.Object
 }
 
-// ObjectList is a Kubernetes object list, allows functions to work indistinctly with any resource that
-// implements both runtime.Object and metav1.ListInterface interfaces.
+// ObjectList is a Kubernetes object list, allows functions to work
+// indistinctly with any resource that implements both runtime.Object and
+// metav1.ListInterface interfaces.
+//
+// Semantically, this is any object which may be serialized (ObjectMeta), and
+// is a kubernetes list wrapper (has items, pagination fields, etc) -- think
+// the wrapper used in a response from a `kubectl list --output yaml` call.
+//
+// Code-wise, this means that any object which embedds both ListMeta (which
+// provides metav1.ListInterface) and TypeMeta (which provides half of
+// runtime.Object) and has a `DeepCopyObject` implementation (the other half of
+// runtime.Object) will implement this by default.
+//
+// For example, nearly all the built-in XYZList types are ObjectLists, as well
+// as the XYZList types for all KubeBuilder-generated CRDs (unless you do
+// something real funky to them).
+//
+// By and large, most things that are XYZList and implement runtime.Object also
+// implement ObjectList -- it's very rare to have *just* a runtime.Object
+// implementation (the cases tend to be funky built-in types like Webhook
+// payloads that don't have a `metadata` field).
+//
+// This is similar to Object, which is almost always implemented by the items
+// in the list themselves.
 type ObjectList interface {
 	metav1.ListInterface
 	runtime.Object