Improve error messages on filtering for Kubernetes-type files. (#95)

slice/errors.go

@@ -1,6 +1,9 @@
 package slice
 
-import "fmt"
+import (
+	"fmt"
+	"strings"
+)
 
 type strictModeSkipErr struct {
 	fieldName string
@@ -20,3 +23,31 @@ type skipErr struct {
 func (e *skipErr) Error() string {
 	return fmt.Sprintf("resource %s %q is configured to be skipped", e.kind, e.name)
 }
+
+const nonK8sHelper = `the file has no Kubernetes metadata: it is most likely a non-Kubernetes YAML file, you can skip it with --skip-non-k8s`
+
+type cantFindFieldErr struct {
+	fieldName string
+	fileCount int
+	meta      kubeObjectMeta
+}
+
+func (e *cantFindFieldErr) Error() string {
+	var sb strings.Builder
+
+	sb.WriteString(fmt.Sprintf(
+		"unable to find Kubernetes %q field in file %d",
+		e.fieldName, e.fileCount,
+	))
+
+	if e.meta.empty() {
+		sb.WriteString(": " + nonK8sHelper)
+	} else {
+		sb.WriteString(fmt.Sprintf(
+			": processed details: kind %q, name %q, apiVersion %q",
+			e.meta.Kind, e.meta.Name, e.meta.APIVersion,
+		))
+	}
+
+	return sb.String()
+}

slice/errors_test.go

@@ -9,6 +9,7 @@ import (
 func TestErrorsInterface(t *testing.T) {
 	require.Implementsf(t, (*error)(nil), &strictModeSkipErr{}, "strictModeSkipErr should implement error")
 	require.Implementsf(t, (*error)(nil), &skipErr{}, "skipErr should implement error")
+	require.Implementsf(t, (*error)(nil), &cantFindFieldErr{}, "cantFindFieldErr should implement error")
 }
 
 func requireErrorIf(t *testing.T, wantErr bool, err error) {

slice/kube.go

@@ -15,6 +15,10 @@ type kubeObjectMeta struct {
 	Namespace  string
 }
 
+func (k kubeObjectMeta) empty() bool {
+	return k.APIVersion == "" && k.Kind == "" && k.Name == "" && k.Namespace == ""
+}
+
 // from: https://github.com/helm/helm/blob/v3.11.1/pkg/releaseutil/kind_sorter.go#LL31-L67C2
 var helmInstallOrder = []string{
 	"Namespace",

slice/process.go

@@ -58,12 +58,12 @@ func (s *Split) parseYAMLManifest(contents []byte) (yamlFile, error) {
 
 	// Check if we have a Kubernetes kind and we're requesting inclusion or exclusion
 	if k8smeta.Kind == "" && !s.opts.AllowEmptyKinds && (hasIncluded || hasExcluded) {
-		return yamlFile{}, fmt.Errorf("unable to find Kubernetes \"kind\" field in file number %d", s.fileCount)
+		return yamlFile{}, &cantFindFieldErr{fieldName: "kind", fileCount: s.fileCount, meta: k8smeta}
 	}
 
 	// Check if we have a Kubernetes name and we're requesting inclusion or exclusion
 	if k8smeta.Name == "" && !s.opts.AllowEmptyNames && (hasIncluded || hasExcluded) {
-		return yamlFile{}, fmt.Errorf("unable to find Kubernetes \"metadata.name\" field in file number %d", s.fileCount)
+		return yamlFile{}, &cantFindFieldErr{fieldName: "metadata.name", fileCount: s.fileCount, meta: k8smeta}
 	}
 
 	// We need to check if the file should be skipped