dry-run: Create class to find if a type is a CRD

Finding out if a Group-version-kind is a CRD is useful, since we want to
detect dry-run ability differently for CRDs.

pkg/kubectl/cmd/util/BUILD

@@ -4,6 +4,7 @@ go_library(
     name = "go_default_library",
     srcs = [
         "conversion.go",
+        "crdfinder.go",
         "factory.go",
         "factory_client_access.go",
         "generator.go",
@@ -34,6 +35,7 @@ go_library(
         "//staging/src/k8s.io/apimachinery/pkg/api/errors:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/api/meta:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1/unstructured:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/runtime/schema:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/util/errors:go_default_library",
@@ -57,7 +59,10 @@ go_library(
 
 go_test(
     name = "go_default_test",
-    srcs = ["helpers_test.go"],
+    srcs = [
+        "crdfinder_test.go",
+        "helpers_test.go",
+    ],
     embed = [":go_default_library"],
     deps = [
         "//pkg/kubectl/scheme:go_default_library",

pkg/kubectl/cmd/util/crdfinder.go

@@ -0,0 +1,108 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"reflect"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/client-go/dynamic"
+)
+
+// CRDGetter is a function that can download the list of GVK for all
+// CRDs.
+type CRDGetter func() ([]schema.GroupKind, error)
+
+func CRDFromDynamic(client dynamic.Interface) CRDGetter {
+	return func() ([]schema.GroupKind, error) {
+		list, err := client.Resource(schema.GroupVersionResource{
+			Group:    "apiextensions.k8s.io",
+			Version:  "v1beta1",
+			Resource: "curstomresourcedefinitions",
+		}).List(metav1.ListOptions{})
+		if err != nil {
+			return nil, err
+		}
+		if list == nil {
+			return nil, nil
+		}
+
+		gks := []schema.GroupKind{}
+
+		// We need to parse the list to get the gvk, I guess that's fine.
+		for _, crd := range (*list).Items {
+			// Look for group, version, and kind
+			group, _, _ := unstructured.NestedString(crd.Object, "spec", "group")
+			kind, _, _ := unstructured.NestedString(crd.Object, "spec", "names", "kind")
+
+			gks = append(gks, schema.GroupKind{
+				Group: group,
+				Kind:  kind,
+			})
+		}
+
+		return gks, nil
+	}
+}
+
+// CRDFinder keeps a cache of known CRDs and finds a given GVK in the
+// list.
+type CRDFinder interface {
+	HasCRD(gvk schema.GroupKind) (bool, error)
+}
+
+func NewCRDFinder(getter CRDGetter) CRDFinder {
+	return &crdFinder{
+		getter: getter,
+	}
+}
+
+type crdFinder struct {
+	getter CRDGetter
+	cache  *[]schema.GroupKind
+}
+
+func (f *crdFinder) cacheCRDs() error {
+	if f.cache != nil {
+		return nil
+	}
+
+	list, err := f.getter()
+	if err != nil {
+		return err
+	}
+	f.cache = &list
+	return nil
+}
+
+func (f *crdFinder) findCRD(gvk schema.GroupKind) bool {
+	for _, crd := range *f.cache {
+		if reflect.DeepEqual(gvk, crd) {
+			return true
+		}
+	}
+	return false
+}
+
+func (f *crdFinder) HasCRD(gvk schema.GroupKind) (bool, error) {
+	if err := f.cacheCRDs(); err != nil {
+		return false, err
+	}
+	return f.findCRD(gvk), nil
+}

pkg/kubectl/cmd/util/crdfinder_test.go

@@ -0,0 +1,89 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util_test
+
+import (
+	"errors"
+	"testing"
+
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/kubernetes/pkg/kubectl/cmd/util"
+)
+
+func TestCacheCRDFinder(t *testing.T) {
+	called := 0
+	getter := func() ([]schema.GroupKind, error) {
+		called += 1
+		return nil, nil
+	}
+	finder := util.NewCRDFinder(getter)
+	if called != 0 {
+		t.Fatalf("Creating the finder shouldn't call the getter, has called = %v", called)
+	}
+	_, err := finder.HasCRD(schema.GroupKind{Group: "", Kind: "Pod"})
+	if err != nil {
+		t.Fatalf("Failed to call HasCRD: %v", err)
+	}
+	if called != 1 {
+		t.Fatalf("First call should call the getter, has called = %v", called)
+	}
+
+	_, err = finder.HasCRD(schema.GroupKind{Group: "", Kind: "Pod"})
+	if err != nil {
+		t.Fatalf("Failed to call HasCRD: %v", err)
+	}
+	if called != 1 {
+		t.Fatalf("Second call should NOT call the getter, has called = %v", called)
+	}
+}
+
+func TestCRDFinderErrors(t *testing.T) {
+	getter := func() ([]schema.GroupKind, error) {
+		return nil, errors.New("not working")
+	}
+	finder := util.NewCRDFinder(getter)
+	found, err := finder.HasCRD(schema.GroupKind{Group: "", Kind: "Pod"})
+	if found == true {
+		t.Fatalf("Found the CRD with non-working getter function")
+	}
+	if err == nil {
+		t.Fatalf("Error in getter should be reported")
+	}
+}
+
+func TestCRDFinder(t *testing.T) {
+	getter := func() ([]schema.GroupKind, error) {
+		return []schema.GroupKind{
+			{
+				Group: "crd.com",
+				Kind:  "MyCRD",
+			},
+			{
+				Group: "crd.com",
+				Kind:  "MyNewCRD",
+			},
+		}, nil
+	}
+	finder := util.NewCRDFinder(getter)
+
+	if found, _ := finder.HasCRD(schema.GroupKind{Group: "crd.com", Kind: "MyCRD"}); !found {
+		t.Fatalf("Failed to find CRD MyCRD")
+	}
+	if found, _ := finder.HasCRD(schema.GroupKind{Group: "crd.com", Kind: "Random"}); found {
+		t.Fatalf("Found crd Random that doesn't exist")
+	}
+}