Improve some map initializations (gardener#8070)

extensions/pkg/controller/controlplane/utils.go

@@ -22,7 +22,7 @@ import (
 
 // MergeSecretMaps merges the 2 given secret maps.
 func MergeSecretMaps(a, b map[string]*corev1.Secret) map[string]*corev1.Secret {
-	x := make(map[string]*corev1.Secret)
+	x := make(map[string]*corev1.Secret, len(a))
 	for _, m := range []map[string]*corev1.Secret{a, b} {
 		for k, v := range m {
 			x[k] = v

pkg/admissioncontroller/seedidentity/identity.go

@@ -73,7 +73,7 @@ func convertAuthenticationV1ExtraValueToUserInfoExtra(extra map[string]authentic
 	if extra == nil {
 		return nil
 	}
-	ret := map[string][]string{}
+	ret := make(map[string][]string, len(extra))
 	for k, v := range extra {
 		ret[k] = v
 	}

pkg/admissioncontroller/webhook/auth/seed/attributes.go

@@ -77,7 +77,7 @@ func convertToUserInfoExtra(extra map[string]authorizationv1.ExtraValue) map[str
 	if extra == nil {
 		return nil
 	}
-	ret := map[string][]string{}
+	ret := make(map[string][]string, len(extra))
 	for k, v := range extra {
 		ret[k] = v
 	}

pkg/apis/core/v1beta1/conversions.go

@@ -120,7 +120,7 @@ func Convert_v1beta1_InternalSecret_To_core_InternalSecret(in *InternalSecret, o
 	// StringData overwrites Data
 	if len(in.StringData) > 0 {
 		if out.Data == nil {
-			out.Data = map[string][]byte{}
+			out.Data = make(map[string][]byte, len(in.StringData))
 		}
 		for k, v := range in.StringData {
 			out.Data[k] = []byte(v)

pkg/apis/core/validation/project.go

@@ -175,7 +175,7 @@ func ValidateProjectMember(member core.ProjectMember, fldPath *field.Path) field
 
 	allErrs = append(allErrs, ValidateSubject(member.Subject, fldPath)...)
 
-	foundRoles := map[string]struct{}{}
+	foundRoles := make(map[string]struct{}, len(member.Roles))
 	for i, role := range member.Roles {
 		rolesPath := fldPath.Child("roles").Index(i)
 

pkg/component/extensions/operatingsystemconfig/original/components/kernelconfig/component.go

@@ -40,7 +40,7 @@ func (component) Name() string {
 }
 
 func (component) Config(ctx components.Context) ([]extensionsv1alpha1.Unit, []extensionsv1alpha1.File, error) {
-	var newData = map[string]string{}
+	var newData = make(map[string]string, len(data))
 
 	for key, value := range data {
 		newData[key] = value

pkg/controllermanager/controller/certificatesigningrequest/reconciler.go

@@ -55,7 +55,6 @@ func (r *Reconciler) Reconcile(ctx context.Context, request reconcile.Request) (
 
 		isInFinalState bool
 		finalState     string
-		extra          = make(map[string]authorizationv1.ExtraValue)
 	)
 
 	ctx, cancel := controllerutils.GetMainReconciliationContext(ctx, controllerutils.DefaultReconciliationTimeout)
@@ -77,6 +76,7 @@ func (r *Reconciler) Reconcile(ctx context.Context, request reconcile.Request) (
 		}
 	}
 
+	extra := make(map[string]authorizationv1.ExtraValue, len(csr.Spec.Extra))
 	for k, v := range csr.Spec.Extra {
 		extra[k] = authorizationv1.ExtraValue(v)
 	}

pkg/operation/operation.go

@@ -215,7 +215,7 @@ func (b *Builder) Build(
 	if err != nil {
 		return nil, err
 	}
-	secrets := make(map[string]*corev1.Secret)
+	secrets := make(map[string]*corev1.Secret, len(secretsMap))
 	for k, v := range secretsMap {
 		secrets[k] = v
 	}

pkg/resourcemanager/controller/managedresource/merger.go

@@ -415,7 +415,7 @@ func mergeServiceAccount(scheme *runtime.Scheme, oldObj, newObj runtime.Object)
 // It takes an optional map of old desired values and removes any keys/values from the resulting map
 // that were once desired (part of `old`) but are not desired anymore.
 func mergeMapsBasedOnOldMap(desired, current, old map[string]string) map[string]string {
-	out := map[string]string{}
+	out := make(map[string]string, len(current))
 	// use current as base
 	for k, v := range current {
 		out[k] = v

pkg/resourcemanager/controller/networkpolicy/reconciler.go

@@ -267,7 +267,7 @@ func (r *Reconciler) reconcileDesiredPolicies(ctx context.Context, service *core
 }
 
 func (r *Reconciler) deleteStalePolicies(networkPolicyList *metav1.PartialObjectMetadataList, desiredObjectMetaKeys []string) []flow.TaskFn {
-	objectMetaKeysForDesiredPolicies := make(map[string]struct{})
+	objectMetaKeysForDesiredPolicies := make(map[string]struct{}, len(desiredObjectMetaKeys))
 	for _, objectMetaKey := range desiredObjectMetaKeys {
 		objectMetaKeysForDesiredPolicies[objectMetaKey] = struct{}{}
 	}

pkg/utils/imagevector/imagevector.go

@@ -349,7 +349,7 @@ func (v ImageVector) FindImage(name string, opts ...FindOptionFunc) (*Image, err
 // In case multiple images match the search, the first which was found is returned.
 // In case no image was found, an error is returned.
 func FindImages(v ImageVector, names []string, opts ...FindOptionFunc) (map[string]*Image, error) {
-	images := map[string]*Image{}
+	images := make(map[string]*Image, len(names))
 	for _, imageName := range names {
 		image, err := v.FindImage(imageName, opts...)
 		if err != nil {

pkg/utils/miscellaneous.go

@@ -40,7 +40,7 @@ func ValueExists(value string, list []string) bool {
 // MergeMaps takes two maps <a>, <b> and merges them. If <b> defines a value with a key
 // already existing in the <a> map, the <a> value for that key will be overwritten.
 func MergeMaps(a, b map[string]interface{}) map[string]interface{} {
-	var values = map[string]interface{}{}
+	var values = make(map[string]interface{}, len(b))
 
 	for i, v := range b {
 		existing, ok := a[i]
@@ -73,7 +73,7 @@ func MergeStringMaps[T any](oldMap map[string]T, newMaps ...map[string]T) map[st
 	var out map[string]T
 
 	if oldMap != nil {
-		out = make(map[string]T)
+		out = make(map[string]T, len(oldMap))
 	}
 	for k, v := range oldMap {
 		out[k] = v

pkg/utils/secrets/basic_auth.go

@@ -80,7 +80,7 @@ func (s *BasicAuthSecretConfig) Generate() (DataInterface, error) {
 
 // SecretData computes the data map which can be used in a Kubernetes secret.
 func (b *BasicAuth) SecretData() map[string][]byte {
-	data := map[string][]byte{}
+	data := make(map[string][]byte, 3)
 
 	data[DataKeyUserName] = []byte(b.Username)
 	data[DataKeyPassword] = []byte(b.Password)

test/framework/shootmigrationtest.go

@@ -254,7 +254,7 @@ func (t *ShootMigrationTest) GetPersistedSecrets(ctx context.Context, seedClient
 		return nil, err
 	}
 
-	secretsMap := map[string]corev1.Secret{}
+	secretsMap := make(map[string]corev1.Secret, len(secretList.Items))
 	for _, secret := range secretList.Items {
 		secretsMap[secret.Name] = secret
 	}

test/utils/shoots/update/update.go

@@ -194,7 +194,7 @@ func verifyKubernetesVersions(ctx context.Context, shootClient kubernetes.Interf
 		return fmt.Errorf("control plane version is %q but expected %q", shootClient.Version(), expectedControlPlaneKubernetesVersion)
 	}
 
-	poolNameToKubernetesVersion := map[string]string{}
+	poolNameToKubernetesVersion := make(map[string]string, len(shoot.Spec.Provider.Workers))
 	for _, worker := range shoot.Spec.Provider.Workers {
 		poolKubernetesVersion, err := v1beta1helper.CalculateEffectiveKubernetesVersion(controlPlaneKubernetesVersion, worker.Kubernetes)
 		if err != nil {