feat: early exit on invalid k8s version flag

cmd/kubeconform/main.go

@@ -84,7 +84,7 @@ func kubeconform(cfg config.Config) int {
 		SkipTLS:              cfg.SkipTLS,
 		SkipKinds:            cfg.SkipKinds,
 		RejectKinds:          cfg.RejectKinds,
-		KubernetesVersion:    cfg.KubernetesVersion,
+		KubernetesVersion:    cfg.KubernetesVersion.String(),
 		Strict:               cfg.Strict,
 		IgnoreMissingSchemas: cfg.IgnoreMissingSchemas,
 	})

pkg/config/config.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"flag"
 	"fmt"
+	"regexp"
 	"strings"
 )
 
@@ -15,7 +16,7 @@ type Config struct {
 	Help                   bool                `yaml:"help" json:"help"`
 	IgnoreFilenamePatterns []string            `yaml:"ignoreFilenamePatterns" json:"ignoreFilenamePatterns"`
 	IgnoreMissingSchemas   bool                `yaml:"ignoreMissingSchemas" json:"ignoreMissingSchemas"`
-	KubernetesVersion      string              `yaml:"kubernetesVersion" json:"kubernetesVersion"`
+	KubernetesVersion      k8sVersionValue     `yaml:"kubernetesVersion" json:"kubernetesVersion"`
 	NumberOfWorkers        int                 `yaml:"numberOfWorkers" json:"numberOfWorkers"`
 	OutputFormat           string              `yaml:"output" json:"output"`
 	RejectKinds            map[string]struct{} `yaml:"reject" json:"reject"`
@@ -39,6 +40,20 @@ func (ap *arrayParam) Set(value string) error {
 	return nil
 }
 
+type k8sVersionValue string
+
+func (kv *k8sVersionValue) String() string {
+	return string(*kv)
+}
+
+func (kv *k8sVersionValue) Set(value string) error {
+	if ok, _ := regexp.MatchString(`^(master|\d+\.\d+\.\d+)$`, value); ok != true {
+		return fmt.Errorf("%v is not a valid version. Valid values are 'master' (default) or full version x.y.z (e.g. '1.27.2')", value)
+	}
+	*kv = k8sVersionValue(value)
+	return nil
+}
+
 func splitCSV(csvStr string) map[string]struct{} {
 	splitValues := strings.Split(csvStr, ",")
 	valuesMap := map[string]struct{}{}
@@ -60,10 +75,10 @@ func FromFlags(progName string, args []string) (Config, string, error) {
 	var buf bytes.Buffer
 	flags.SetOutput(&buf)
 
-	c := Config{}
+	c := Config{KubernetesVersion: "master"}
 	c.Files = []string{}
 
-	flags.StringVar(&c.KubernetesVersion, "kubernetes-version", "master", "version of Kubernetes to validate against, e.g.: 1.18.0")
+	flags.Var(&c.KubernetesVersion, "kubernetes-version", "version of Kubernetes to validate against, e.g.: 1.18.0")
 	flags.Var(&schemaLocationsParam, "schema-location", "override schemas location search path (can be specified multiple times)")
 	flags.StringVar(&skipKindsCSV, "skip", "", "comma-separated list of kinds or GVKs to ignore")
 	flags.StringVar(&rejectKindsCSV, "reject", "", "comma-separated list of kinds or GVKs to reject")

pkg/config/config_test.go

@@ -138,3 +138,34 @@ func TestFromFlags(t *testing.T) {
 		}
 	}
 }
+
+func TestKubernetesVersionFlag(t *testing.T) {
+	for _, testCase := range []struct {
+		k8sVersion  string
+		expectError bool
+	}{
+		{
+			"master",
+			false,
+		},
+		{
+			"1.2.3",
+			false,
+		},
+		{
+			"1.2",
+			true,
+		},
+		{
+			"foo",
+			true,
+		},
+	} {
+		_, _, err := FromFlags("kubeconform", []string{"-kubernetes-version", testCase.k8sVersion})
+		if testCase.expectError && err == nil {
+			t.Errorf("expected error for kubernetes version flag %s", testCase.k8sVersion)
+		} else if !testCase.expectError && err != nil {
+			t.Errorf("unexpected error for kubernetes version flag %s: %s", testCase.k8sVersion, err)
+		}
+	}
+}