fail early when a broken -schema-location template is given

acceptance.bats

@@ -128,6 +128,13 @@
   [ "$status" -eq 1 ]
 }
 
+@test "Fail early when passing a non valid -schema-location template" {
+  run bin/kubeconform -schema-location 'foo {{ .Foo }}' fixtures/valid.yaml
+  [[ "$output" = failed\ initialising* ]]
+  [[ `echo "$output" | wc -l` -eq 1 ]]
+  [ "$status" -eq 1 ]
+}
+
 @test "Pass with a valid input when validating against openshift manifests" {
   run bin/kubeconform -kubernetes-version 3.8.0  -schema-location 'https://raw.githubusercontent.com/garethr/openshift-json-schema/master/{{ .NormalizedKubernetesVersion }}-standalone{{ .StrictSuffix }}/{{ .ResourceKind }}.json'  -summary fixtures/valid.yaml
   [ "$status" -eq 0 ]

cmd/kubeconform/main.go

@@ -65,7 +65,7 @@ func realMain() int {
 		return 1
 	}
 
-	v := validator.New(cfg.SchemaLocations, validator.Opts{
+	v, err := validator.New(cfg.SchemaLocations, validator.Opts{
 		SkipTLS:              cfg.SkipTLS,
 		SkipKinds:            cfg.SkipKinds,
 		RejectKinds:          cfg.RejectKinds,
@@ -73,6 +73,10 @@ func realMain() int {
 		Strict:               cfg.Strict,
 		IgnoreMissingSchemas: cfg.IgnoreMissingSchemas,
 	})
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		return 1
+	}
 
 	validationResults := make(chan validator.Result)
 	ctx := context.Background()

examples/main.go

@@ -16,7 +16,10 @@ func main() {
 		log.Fatalf("failed opening %s: %s", filepath, err)
 	}
 
-	v := validator.New(nil, validator.Opts{Strict: true})
+	v, err := validator.New(nil, validator.Opts{Strict: true})
+	if err != nil {
+		log.Fatalf("failed initializing validator: %s", err)
+	}
 	for i, res := range v.Validate(filepath, f) { // A file might contain multiple resources
 		// File starts with ---, the parser assumes a first empty resource
 		if res.Status == validator.Invalid {

pkg/registry/registry.go

@@ -2,6 +2,7 @@ package registry
 
 import (
 	"bytes"
+	"fmt"
 	"strings"
 	"text/template"
 )
@@ -67,14 +68,19 @@ func schemaPath(tpl, resourceKind, resourceAPIVersion, k8sVersion string, strict
 	return buf.String(), nil
 }
 
-func New(schemaLocation string, strict bool, skipTLS bool) Registry {
+func New(schemaLocation string, strict bool, skipTLS bool) (Registry, error) {
 	if !strings.HasSuffix(schemaLocation, "json") { // If we dont specify a full templated path, we assume the paths of kubernetesjsonschema.dev
 		schemaLocation += "/{{ .NormalizedKubernetesVersion }}-standalone{{ .StrictSuffix }}/{{ .ResourceKind }}{{ .KindSuffix }}.json"
 	}
 
+	// We try a fake compilation of the schemaLocation template to ensure it is valid
+	if _, err := schemaPath(schemaLocation, "Deployment", "v1", "1.18.0", true); err != nil {
+		return nil, fmt.Errorf("failed initialising schema location registry: %s", err)
+	}
+
 	if strings.HasPrefix(schemaLocation, "http") {
-		return newHTTPRegistry(schemaLocation, strict, skipTLS)
+		return newHTTPRegistry(schemaLocation, strict, skipTLS), nil
 	} else {
-		return newLocalRegistry(schemaLocation, strict)
+		return newLocalRegistry(schemaLocation, strict), nil
 	}
 }

pkg/validator/validator.go

@@ -51,7 +51,7 @@ type Opts struct {
 }
 
 // New returns a new Validator
-func New(schemaLocations []string, opts Opts) Validator {
+func New(schemaLocations []string, opts Opts) (Validator, error) {
 	// Default to kubernetesjsonschema.dev
 	if schemaLocations == nil || len(schemaLocations) == 0 {
 		schemaLocations = []string{"https://kubernetesjsonschema.dev"}
@@ -59,7 +59,11 @@ func New(schemaLocations []string, opts Opts) Validator {
 
 	registries := []registry.Registry{}
 	for _, schemaLocation := range schemaLocations {
-		registries = append(registries, registry.New(schemaLocation, opts.Strict, opts.SkipTLS))
+		reg, err := registry.New(schemaLocation, opts.Strict, opts.SkipTLS)
+		if err != nil {
+			return nil, err
+		}
+		registries = append(registries, reg)
 	}
 
 	if opts.KubernetesVersion == "" {
@@ -78,7 +82,7 @@ func New(schemaLocations []string, opts Opts) Validator {
 		schemaDownload: downloadSchema,
 		schemaCache:    cache.New(),
 		regs:           registries,
-	}
+	}, nil
 }
 
 type v struct {