Merge pull request #608 from ingvagabund/backport-91295

UPSTREAM: 91295: kubectl explain: detect resource group in case there…

staging/src/k8s.io/kubectl/pkg/cmd/explain/explain.go

@@ -120,12 +120,22 @@ func (o *ExplainOptions) Run(args []string) error {
 	recursive := o.Recursive
 	apiVersionString := o.APIVersion
 
-	// TODO: After we figured out the new syntax to separate group and resource, allow
-	// the users to use it in explain (kubectl explain <group><syntax><resource>).
-	// Refer to issue #16039 for why we do this. Refer to PR #15808 that used "/" syntax.
-	fullySpecifiedGVR, fieldsPath, err := explain.SplitAndParseResourceRequest(args[0], o.Mapper)
-	if err != nil {
-		return err
+	var fullySpecifiedGVR schema.GroupVersionResource
+	var fieldsPath []string
+	var err error
+	if len(apiVersionString) == 0 {
+		fullySpecifiedGVR, fieldsPath, err = explain.SplitAndParseResourceRequestWithMatchingPrefix(args[0], o.Mapper)
+		if err != nil {
+			return err
+		}
+	} else {
+		// TODO: After we figured out the new syntax to separate group and resource, allow
+		// the users to use it in explain (kubectl explain <group><syntax><resource>).
+		// Refer to issue #16039 for why we do this. Refer to PR #15808 that used "/" syntax.
+		fullySpecifiedGVR, fieldsPath, err = explain.SplitAndParseResourceRequest(args[0], o.Mapper)
+		if err != nil {
+			return err
+		}
 	}
 
 	gvk, _ := o.Mapper.KindFor(fullySpecifiedGVR)

staging/src/k8s.io/kubectl/pkg/explain/explain.go

@@ -50,6 +50,43 @@ func SplitAndParseResourceRequest(inResource string, mapper meta.RESTMapper) (sc
 	if err != nil {
 		return schema.GroupVersionResource{}, nil, err
 	}
+
+	return gvr, fieldsPath, nil
+}
+
+// SplitAndParseResourceRequestWithMatchingPrefix separates the users input into a model and fields
+// while selecting gvr whose (resource, group) prefix matches the resource
+func SplitAndParseResourceRequestWithMatchingPrefix(inResource string, mapper meta.RESTMapper) (gvr schema.GroupVersionResource, fieldsPath []string, err error) {
+	// ignore trailing period
+	inResource = strings.TrimSuffix(inResource, ".")
+	dotParts := strings.Split(inResource, ".")
+
+	gvrs, err := mapper.ResourcesFor(schema.GroupVersionResource{Resource: dotParts[0]})
+	if err != nil {
+		return schema.GroupVersionResource{}, nil, err
+	}
+
+	for _, gvrItem := range gvrs {
+		// Find first gvr whose gr prefixes requested resource
+		groupResource := gvrItem.GroupResource().String()
+		if strings.HasPrefix(inResource, groupResource) {
+			resourceSuffix := inResource[len(groupResource):]
+			if len(resourceSuffix) > 0 {
+				dotParts := strings.Split(resourceSuffix, ".")
+				if len(dotParts) > 0 {
+					fieldsPath = dotParts[1:]
+				}
+			}
+			return gvrItem, fieldsPath, nil
+		}
+	}
+
+	// If no match, take the first (the highest priority) gvr
+	if len(gvrs) > 0 {
+		gvr = gvrs[0]
+		_, fieldsPath = splitDotNotation(inResource)
+	}
+
 	return gvr, fieldsPath, nil
 }