Feature/read from stdin (#1165)

* temp

* added pipe logic for apply

* removed comments

* updated readme

documentation/kyverno-cli.md

@@ -36,7 +36,7 @@ yay -S kyverno-git
 
 ## Commands
 
-#### Version
+### Version
 
 Prints the version of kyverno used by the CLI.
 
@@ -45,7 +45,7 @@ Example:
 kyverno version
 ```
 
-#### Validate
+### Validate
 Validates a policy, can validate multiple policy resource description files or even an entire folder containing policy resource description 
 files. Currently supports files with resource description in yaml.
 
@@ -68,7 +68,7 @@ Example:
 kyverno validate /path/to/policy1.yaml -c /path/to/crd.yaml -c /path/to/folderFullOfCRDs
 ```
 
-#### Apply
+### Apply
 Applies policies on resources, and supports applying multiple policies on multiple resources in a single command.
 Also supports applying the given policies to an entire cluster. The current kubectl context will be used to access the cluster.
 
@@ -84,6 +84,11 @@ Apply to all matching resources in a cluster:
 kyverno apply /path/to/policy.yaml --cluster > policy-results.txt
 ```
 
+The resources can also be passed from stdin:
+```
+kustomize build nginx/overlays/envs/prod/ | kyverno apply /path/to/policy.yaml --resource -
+```
+
 Apply multiple policies to multiple resources:
 ```
 kyverno apply /path/to/policy1.yaml /path/to/folderFullOfPolicies --resource /path/to/resource1.yaml --resource /path/to/resource2.yaml --cluster

pkg/kyverno/apply/command.go

@@ -1,6 +1,7 @@
 package apply
 
 import (
+	"bufio"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -170,9 +171,26 @@ func Command() *cobra.Command {
 				}
 			}
 
-			resources, err := getResources(policies, resourcePaths, dClient)
-			if err != nil {
-				return sanitizedError.NewWithError("failed to load resources", err)
+			var resources []*unstructured.Unstructured
+			if resourcePaths[0] == "-" {
+				if isInputFromPipe() {
+					resourceStr := ""
+					scanner := bufio.NewScanner(os.Stdin)
+					for scanner.Scan() {
+						resourceStr = resourceStr + scanner.Text() + "\n"
+					}
+
+					yamlBytes := []byte(resourceStr)
+					resources, err = getResource(yamlBytes)
+					if err != nil {
+						return sanitizedError.NewWithError("failed to extract the resources", err)
+					}
+				}
+			} else {
+				resources, err = getResources(policies, resourcePaths, dClient)
+				if err != nil {
+					return sanitizedError.NewWithError("failed to load resources", err)
+				}
 			}
 
 			mutatedPolicies, err := mutatePolices(policies)
@@ -279,7 +297,11 @@ func getResources(policies []*v1.ClusterPolicy, resourcePaths []string, dClient
 	}
 
 	for _, resourcePath := range resourcePaths {
-		getResources, err := getResource(resourcePath)
+		resourceBytes, err := getFileBytes(resourcePath)
+		if err != nil {
+			return nil, err
+		}
+		getResources, err := getResource(resourceBytes)
 		if err != nil {
 			return nil, err
 		}
@@ -315,62 +337,32 @@ func getResourcesOfTypeFromCluster(resourceTypes []string, dClient *client.Clien
 	return resources, nil
 }
 
-func getResource(path string) ([]*unstructured.Unstructured, error) {
-
-	resources := make([]*unstructured.Unstructured, 0)
-	getResourceErrors := make([]error, 0)
-
+func getFileBytes(path string) ([]byte, error) {
 	file, err := ioutil.ReadFile(path)
 	if err != nil {
 		return nil, err
 	}
+	return file, err
+}
 
-	files, splitDocError := utils.SplitYAMLDocuments(file)
+func getResource(resourceBytes []byte) ([]*unstructured.Unstructured, error) {
+	resources := make([]*unstructured.Unstructured, 0)
+	var getErrString string
+
+	files, splitDocError := utils.SplitYAMLDocuments(resourceBytes)
 	if splitDocError != nil {
 		return nil, splitDocError
 	}
 
 	for _, resourceYaml := range files {
-
-		decode := scheme.Codecs.UniversalDeserializer().Decode
-		resourceObject, metaData, err := decode(resourceYaml, nil, nil)
+		resource, err := convertResourceToUnstructured(resourceYaml)
 		if err != nil {
-			getResourceErrors = append(getResourceErrors, err)
-			continue
-		}
-
-		resourceUnstructured, err := runtime.DefaultUnstructuredConverter.ToUnstructured(&resourceObject)
-		if err != nil {
-			getResourceErrors = append(getResourceErrors, err)
-			continue
-		}
-
-		resourceJSON, err := json.Marshal(resourceUnstructured)
-		if err != nil {
-			getResourceErrors = append(getResourceErrors, err)
-			continue
-		}
-
-		resource, err := engineutils.ConvertToUnstructured(resourceJSON)
-		if err != nil {
-			getResourceErrors = append(getResourceErrors, err)
-			continue
-		}
-
-		resource.SetGroupVersionKind(*metaData)
-
-		if resource.GetNamespace() == "" {
-			resource.SetNamespace("default")
+			getErrString = getErrString + err.Error() + "\n"
 		}
 
 		resources = append(resources, resource)
 	}
 
-	var getErrString string
-	for _, getResourceError := range getResourceErrors {
-		getErrString = getErrString + getResourceError.Error() + "\n"
-	}
-
 	if getErrString != "" {
 		return nil, errors.New(getErrString)
 	}
@@ -378,6 +370,36 @@ func getResource(path string) ([]*unstructured.Unstructured, error) {
 	return resources, nil
 }
 
+func convertResourceToUnstructured(resourceYaml []byte) (*unstructured.Unstructured, error) {
+	decode := scheme.Codecs.UniversalDeserializer().Decode
+	resourceObject, metaData, err := decode(resourceYaml, nil, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	resourceUnstructured, err := runtime.DefaultUnstructuredConverter.ToUnstructured(&resourceObject)
+	if err != nil {
+		return nil, err
+	}
+
+	resourceJSON, err := json.Marshal(resourceUnstructured)
+	if err != nil {
+		return nil, err
+	}
+
+	resource, err := engineutils.ConvertToUnstructured(resourceJSON)
+	if err != nil {
+		return nil, err
+	}
+
+	resource.SetGroupVersionKind(*metaData)
+
+	if resource.GetNamespace() == "" {
+		resource.SetNamespace("default")
+	}
+	return resource, nil
+}
+
 // applyPolicyOnResource - function to apply policy on resource
 func applyPolicyOnResource(policy *v1.ClusterPolicy, resource *unstructured.Unstructured, mutateLogPath string, mutateLogPathIsDir bool, variables map[string]string, rc *resultCounts) error {
 	responseError := false
@@ -566,3 +588,8 @@ func createFileOrFolder(mutateLogPath string, mutateLogPathIsDir bool) error {
 
 	return nil
 }
+
+func isInputFromPipe() bool {
+	fileInfo, _ := os.Stdin.Stat()
+	return fileInfo.Mode()&os.ModeCharDevice == 0
+}