Updating checkIfInstallable to handle multiple chart apiVersions

Signed-off-by: Matt Farina <matt.farina@suse.com>

cmd/helm/install.go

@@ -31,8 +31,9 @@ import (
 	"github.com/spf13/pflag"
 
 	"helm.sh/helm/v4/cmd/helm/require"
+	ichart "helm.sh/helm/v4/internal/chart"
 	"helm.sh/helm/v4/pkg/action"
-	chart "helm.sh/helm/v4/pkg/chart/v2"
+	chartv2 "helm.sh/helm/v4/pkg/chart/v2"
 	"helm.sh/helm/v4/pkg/chart/v2/loader"
 	"helm.sh/helm/v4/pkg/cli/output"
 	"helm.sh/helm/v4/pkg/cli/values"
@@ -327,12 +328,21 @@ func runInstall(args []string, client *action.Install, valueOpts *values.Options
 // checkIfInstallable validates if a chart can be installed
 //
 // Application chart type is only installable
-func checkIfInstallable(ch *chart.Chart) error {
-	switch ch.Metadata.Type {
-	case "", "application":
-		return nil
+func checkIfInstallable(ch ichart.Chart) error {
+
+	// In order to access nested structs (i.e., Metadata) you need to do type switches as generics
+	// do not provide a means to handle accessing these.
+	switch v := any(ch).(type) {
+	case *chartv2.Chart:
+		switch v.Metadata.Type {
+		case "", "application":
+			return nil
+		}
+
+		return errors.Errorf("%s charts are not installable", v.Metadata.Type)
+	default:
+		return errors.Errorf("chart type cannot be installed, type: %T\n", v)
 	}
-	return errors.Errorf("%s charts are not installable", ch.Metadata.Type)
 }
 
 // Provide dynamic auto-completion for the install and template commands

internal/chart/chart.go

@@ -0,0 +1,23 @@
+/*
+Copyright The Helm Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+package chart
+
+// Chart provides an interface between multiple types of charts.
+//
+// Chat provides a union between different Chart versions so that functions and generics can work
+// with one type. Note, chart v2 handles apiVersion v1 and v2 charts.
+// TODO(mattfarina): Add chart v3 here.
+type Chart interface{}