Check if targeted version is supported by binary

Signed-off-by: Hidde Beydals <hello@hidde.co>

cmd/flux/bootstrap.go

@@ -141,6 +141,10 @@ func generateInstallManifests(targetPath, namespace, tmpDir string, localManifes
 		}
 	}
 
+	if !utils.CompatibleVersion(VERSION, bootstrapArgs.version) {
+		return "", fmt.Errorf("targeted version '%s' is not compatible with your current version of flux (%s)", bootstrapArgs.version, VERSION)
+	}
+
 	opts := install.Options{
 		BaseURL:                localManifests,
 		Version:                bootstrapArgs.version,

cmd/flux/install.go

@@ -126,6 +126,10 @@ func installCmdRun(cmd *cobra.Command, args []string) error {
 		}
 	}
 
+	if !utils.CompatibleVersion(VERSION, installVersion) {
+		return fmt.Errorf("targeted version '%s' is not compatible with your current version of flux (%s)", installVersion, VERSION)
+	}
+
 	tmpDir, err := ioutil.TempDir("", rootArgs.namespace)
 	if err != nil {
 		return err

internal/utils/utils.go

@@ -46,14 +46,16 @@ import (
 	kustypes "sigs.k8s.io/kustomize/api/types"
 	"sigs.k8s.io/yaml"
 
-	"github.com/fluxcd/flux2/pkg/manifestgen/install"
 	helmv2 "github.com/fluxcd/helm-controller/api/v2beta1"
 	imageautov1 "github.com/fluxcd/image-automation-controller/api/v1alpha1"
 	imagereflectv1 "github.com/fluxcd/image-reflector-controller/api/v1alpha1"
 	kustomizev1 "github.com/fluxcd/kustomize-controller/api/v1beta1"
 	notificationv1 "github.com/fluxcd/notification-controller/api/v1beta1"
 	"github.com/fluxcd/pkg/runtime/dependency"
+	"github.com/fluxcd/pkg/version"
 	sourcev1 "github.com/fluxcd/source-controller/api/v1beta1"
+
+	"github.com/fluxcd/flux2/pkg/manifestgen/install"
 )
 
 type Utils struct {
@@ -420,3 +422,23 @@ func MergeMaps(a, b map[string]interface{}) map[string]interface{} {
 	}
 	return out
 }
+
+// CompatibleVersion returns if the provided binary version is compatible
+// with the given target version. At present, this is true if the target
+// version is equal to the MINOR range of the binary, or if the binary
+// version is a prerelease.
+func CompatibleVersion(binary, target string) bool {
+	binSv, err := version.ParseVersion(binary)
+	if err != nil {
+		return false
+	}
+	// Assume prerelease builds are compatible.
+	if binSv.Prerelease() != "" {
+		return true
+	}
+	targetSv, err := version.ParseVersion(target)
+	if err != nil {
+		return false
+	}
+	return binSv.Major() == targetSv.Major() && binSv.Minor() == targetSv.Minor()
+}

internal/utils/utils_test.go

@@ -0,0 +1,42 @@
+/*
+Copyright 2021 The Flux 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 utils
+
+import "testing"
+
+func TestCompatibleVersion(t *testing.T) {
+	tests := []struct {
+		name   string
+		binary string
+		target string
+		want   bool
+	}{
+		{"different major version", "1.1.0", "0.1.0", false},
+		{"different minor version", "0.1.0", "0.2.0", false},
+		{"same version", "0.1.0", "0.1.0", true},
+		{"binary patch version ahead", "0.1.1", "0.1.0", true},
+		{"target patch version ahead", "0.1.1", "0.1.2", true},
+		{"prerelease binary", "0.0.0-dev.0", "0.1.0", true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := CompatibleVersion(tt.binary, tt.target); got != tt.want {
+				t.Errorf("CompatibleVersion() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}