add new template functions to list objects (#343)

* add new template functions to list objects

* update docs

Author: cbarbian-sap

internal/templatex/functions.go

@@ -16,10 +16,12 @@ import (
 	"text/template"
 
 	"github.com/pkg/errors"
+	"github.com/sap/go-generics/slices"
 	"github.com/spf13/cast"
 
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/apimachinery/pkg/labels"
 	apitypes "k8s.io/apimachinery/pkg/types"
 	"k8s.io/client-go/tools/clientcmd"
 	"sigs.k8s.io/controller-runtime/pkg/client"
@@ -55,6 +57,7 @@ func FuncMap() template.FuncMap {
 		"formatIPv4Address":        formatIPv4Address,
 		"lookupWithKubeConfig":     makeFuncLookupWithKubeConfig(true),
 		"mustLookupWithKubeConfig": makeFuncLookupWithKubeConfig(false),
+		"lookupListWithKubeConfig": makeFuncLookupListWithKubeConfig(),
 	}
 }
 
@@ -71,6 +74,7 @@ func FuncMapForClient(c client.Client) template.FuncMap {
 	return template.FuncMap{
 		"lookup":     makeFuncLookup(c, true),
 		"mustLookup": makeFuncLookup(c, false),
+		"lookupList": makeFuncLookupList(c),
 	}
 }
 
@@ -79,6 +83,7 @@ func FuncMapForLocalClient(c client.Client) template.FuncMap {
 	return template.FuncMap{
 		"localLookup":     makeFuncLookup(c, true),
 		"mustLocalLookup": makeFuncLookup(c, false),
+		"localLookupList": makeFuncLookupList(c),
 	}
 }
 
@@ -312,3 +317,43 @@ func makeFuncLookupWithKubeConfig(ignoreNotFound bool) func(string, string, stri
 		return object.UnstructuredContent(), nil
 	}
 }
+
+func makeFuncLookupList(c client.Client) func(string, string, string, string) ([]map[string]any, error) {
+	return func(apiVersion string, kind string, namespace string, labelSelector string) ([]map[string]any, error) {
+		objectList := &unstructured.UnstructuredList{}
+		objectList.SetAPIVersion(apiVersion)
+		objectList.SetKind(kind)
+		selector, err := labels.Parse(labelSelector)
+		if err != nil {
+			return nil, err
+		}
+		if err := c.List(context.Background(), objectList, client.InNamespace(namespace), client.MatchingLabelsSelector{Selector: selector}); err != nil {
+			return nil, err
+		}
+		return slices.Collect(objectList.Items, func(object unstructured.Unstructured) map[string]any { return object.UnstructuredContent() }), nil
+	}
+}
+
+func makeFuncLookupListWithKubeConfig() func(string, string, string, string, string) ([]map[string]any, error) {
+	return func(apiVersion string, kind string, namespace string, labelSelector string, kubeConfig string) ([]map[string]any, error) {
+		cfg, err := clientcmd.RESTConfigFromKubeConfig([]byte(kubeConfig))
+		if err != nil {
+			return nil, err
+		}
+		c, err := client.New(cfg, client.Options{})
+		if err != nil {
+			return nil, err
+		}
+		objectList := &unstructured.UnstructuredList{}
+		objectList.SetAPIVersion(apiVersion)
+		objectList.SetKind(kind)
+		selector, err := labels.Parse(labelSelector)
+		if err != nil {
+			return nil, err
+		}
+		if err := c.List(context.Background(), objectList, client.InNamespace(namespace), client.MatchingLabelsSelector{Selector: selector}); err != nil {
+			return nil, err
+		}
+		return slices.Collect(objectList.Items, func(object unstructured.Unstructured) map[string]any { return object.UnstructuredContent() }), nil
+	}
+}

website/content/en/docs/generators/kustomize.md

@@ -47,6 +47,9 @@ and the well-known template function set that is available in Helm can be used;
 | `mustLocalLookup <apiVersion string, kind string, namespace string, name string>`                                  | Lookup a Kubernetes resource with the local client; fail in case of 404 (not found) errors. |
 | `lookupWithKubeConfig <apiVersion string, kind string, namespace string, name string kubeConfig string> `          | Lookup a Kubernetes resource with the given kubeconfig; return nil in case of 404 (not found) errors. |
 | `mustLookupWithKubeConfig <apiVersion string, kind string, namespace string, name string, kubeConfig string>`      | Lookup a Kubernetes resource with the given kubeconfig; fail in case of 404 (not found) errors. |
+| `lookupList <apiVersion string, kind string, namespace string, labelSelector string>`                                           | Lookup (list) Kubernetes resources with the target client. |
+| `localLookupList <apiVersion string, kind string, namespace string, labelSelector string>`                                      | Lookup (list) Kubernetes resources with the local client. |
+| `lookupListWithKubeConfig <apiVersion string, kind string, namespace string, labelSelector string kubeConfig string> `          | Lookup (list) Kubernetes resources with the given kubeconfig. |
 | `listFiles <pattern string>`                                                                                       | List files relative to the provided kustomization directory,  matching the given [pattern](https://pkg.go.dev/github.com/gobwas/glob). | 
 | `existsFile <path string>`                                                                                         | Check if the given file path exists, relative to the provided kustomization directory. |
 | `readFile <path string>`                                                                                           | Read the given file, relative to the provided kustomization directory. |