Add lookupClusterClaim

This new function has basically the same functionality as using the
`lookup` function, in particular it does not stop the templating with an
error if the specified ClusterClaim does not exist. This is especially
helpful for ClusterClaims (in comparison to the analogous functions for
ConfigMaps and Secrets) because the apiVersion for ClusterClaims is
quite long and error-prone to read/write.

Refs:
 - https://issues.redhat.com/browse/ACM-18626

Signed-off-by: Justin Kulikauskas <jkulikau@redhat.com>

Author: JustinKuli

README.md

@@ -42,12 +42,13 @@ Function | Description | Example
 `base64enc` | Decodes the input Base64 string to its decoded form. |`{{ "VGVtcGxhdGVzIHJvY2shCg==" \| base64dec }}`
 `base64enc` | Encodes an input string in the Base64 format. | `{{ "Templating rocks!" \| base64enc }}`
 `indent` | Indents the input string by the specified amount. | `{{ "Templating\nrocks!" \| indent 4 }}`
-`fromClusterClaim` | Returns the value of a specific `ClusterClaim`. | `{{ fromClusterClaim "name" }}`
-`fromConfigMap` | Returns the value of a key inside a `ConfigMap`. | `{{ fromConfigMap "namespace" "config-map-name" "key" }}`
+`fromClusterClaim` | Returns the value of a specific `ClusterClaim`. Errors if the `ClusterClaim` is not found. | `{{ fromClusterClaim "name" }}`
+`lookupClusterClaim` | Returns the value of a specific `ClusterClaim`. Returns an empty string if the `ClusterClaim` is not found. | `{{ lookupClusterClaim "name" }}`
+`fromConfigMap` | Returns the value of a key inside a `ConfigMap`. Errors if the `ConfigMap` is not found. | `{{ fromConfigMap "namespace" "config-map-name" "key" }}`
 `copyConfigMapData` | Returns the `data` contents of the specified `ConfigMap` | `{{ copyConfigMapData "namespace" "config-map-name" }}`
-`fromSecret` | Returns the value of a key inside a `Secret`. If the `EncryptionMode` is set to `EncryptionEnabled`, this will return an encrypted value. | `{{ fromSecret "namespace" "secret-name" "key" }}`
+`fromSecret` | Returns the value of a key inside a `Secret`. If the `EncryptionMode` is set to `EncryptionEnabled`, this will return an encrypted value. Errors if the `Secret` is not found. | `{{ fromSecret "namespace" "secret-name" "key" }}`
 `copySecretData` | Returns the `data` contents of the specified `Secret`. If the `EncryptionMode` is set to `EncryptionEnabled`, this will return an encrypted value. | `{{ copySecretData "namespace" "secret-name" }}`
-`lookup` | Generic lookup function for any Kubernetes object. | `{{ (lookup "v1" "Secret" "namespace" "name").data.key }}`
+`lookup` | Generic lookup function for any Kubernetes object. Returns an empty string if the resource is not found. | `{{ (lookup "v1" "Secret" "namespace" "name").data.key }}`
 `protect` | Encrypts any string using AES-CBC. | `{{ "super-secret" \| protect }}`
 `toBool` | Parses an input boolean string converts it to a boolean but also removes any quotes around the map value. | `key: "{{ "true" \| toBool }}"` => `key: true`
 `toInt` | Parses an input string and returns an integer but also removes anyquotes around the map value. |  `key: "{{ "6" \| toInt }}"` => `key: 6`

pkg/templates/clusterconfig_funcs.go

@@ -6,6 +6,8 @@ package templates
 import (
 	"errors"
 	"fmt"
+
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 )
 
 const clusterClaimAPIVersion string = "cluster.open-cluster-management.io/v1alpha1"
@@ -40,3 +42,37 @@ func (t *TemplateResolver) fromClusterClaim(options *ResolveOptions, claimName s
 
 	return value, nil
 }
+
+func (t *TemplateResolver) lookupClusterClaimHelper(options *ResolveOptions) func(string) (string, error) {
+	return func(claimName string) (string, error) {
+		return t.lookupClusterClaim(options, claimName)
+	}
+}
+
+func (t *TemplateResolver) lookupClusterClaim(options *ResolveOptions, claimName string) (string, error) {
+	if claimName == "" {
+		return "", errors.New("a claim name must be provided")
+	}
+
+	clusterClaim, err := t.getOrList(options, nil, clusterClaimAPIVersion, "ClusterClaim", "", claimName)
+	if err != nil {
+		if apierrors.IsNotFound(err) {
+			return "", nil
+		}
+
+		return "", err
+	}
+
+	spec, ok := clusterClaim["spec"].(map[string]interface{})
+	if !ok {
+		return "", fmt.Errorf("unexpected ClusterClaim format: %s", claimName)
+	}
+
+	var value string
+
+	if _, ok := spec["value"]; ok {
+		value = spec["value"].(string)
+	}
+
+	return value, nil
+}

pkg/templates/clusterconfig_funcs_test.go

@@ -30,10 +30,26 @@ func TestFromClusterClaimNotFound(t *testing.T) {
 
 	expectedMsg := `clusterclaims.cluster.open-cluster-management.io "something-nonexistent" not found`
 	if err == nil || err.Error() != expectedMsg {
-		t.Fatalf("Expected an error for the missing claim name but got %v", err)
+		t.Fatalf("Expected an error for the missing claim but got %v", err)
 	}
 
 	if rv != "" {
 		t.Fatalf("Expected no return value due to the error but got %v", rv)
 	}
 }
+
+func TestLookupClusterClaimNotFound(t *testing.T) {
+	resolver, err := NewResolver(k8sConfig, Config{})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rv, err := resolver.lookupClusterClaim(&ResolveOptions{}, "something-nonexistent")
+	if err != nil {
+		t.Fatalf("Expected no error for the missing claim, but got %v", err)
+	}
+
+	if rv != "" {
+		t.Fatalf("Expected empty return value but got %v", rv)
+	}
+}

pkg/templates/templates.go

@@ -613,6 +613,7 @@ func (t *TemplateResolver) ResolveTemplate(
 		"fromSecret":             t.fromSecretHelper(options, &resolvedResult),
 		"fromConfigMap":          t.fromConfigMapHelper(options),
 		"fromClusterClaim":       t.fromClusterClaimHelper(options),
+		"lookupClusterClaim":     t.lookupClusterClaimHelper(options),
 		"getNodesWithExactRoles": t.getNodesWithExactRolesHelper(options, &resolvedResult),
 		"hasNodesWithExactRoles": t.hasNodesWithExactRolesHelper(options),
 		"lookup":                 t.lookupHelper(options, &resolvedResult),

pkg/templates/templates_test.go

@@ -677,6 +677,14 @@ func TestResolveTemplateDefaultConfig(t *testing.T) {
 			inputTmpl:      `value: '{{ fromClusterClaim "env" }}'`,
 			expectedResult: "value: dev",
 		},
+		"lookupClusterClaim": {
+			inputTmpl:      `value: '{{ lookupClusterClaim "env" }}'`,
+			expectedResult: "value: dev",
+		},
+		"lookupClusterClaim_NonExist": {
+			inputTmpl:      `value: '{{ lookupClusterClaim "nonexist" }}'`,
+			expectedResult: `value: ""`,
+		},
 		"lookup_duplicate_list_uses_resolve_cache": {
 			inputTmpl: `data: '{{ (index (lookup "v1" "ConfigMap" "testns" "" "env=a").items 0).data.cmkey1 }}` +
 				`{{ (index (lookup "v1" "ConfigMap" "testns" "" "env=a").items 0).data.cmkey1 }}'`,