Make validation error similar and explicit for both metadatas

Signed-off-by: Benoit Tigeot <benoit.tigeot@lifen.fr>

internal/plugin/metadata_legacy.go

@@ -68,11 +68,11 @@ type MetadataLegacy struct {
 }
 
 func (m *MetadataLegacy) Validate() error {
-	if !validPluginName.MatchString(m.Name) {
 	if m.Name == "" {
-			return fmt.Errorf("plugin name is empty or missing: ensure plugin.yaml contains 'name:' field (lowercase)")
+		return fmt.Errorf("missing plugin name")
 	}
-		return fmt.Errorf("invalid plugin name %q: plugin names can only contain ASCII characters a-z, A-Z, 0-9, _ and -", m.Name)
+	if !validPluginName.MatchString(m.Name) {
+		return fmt.Errorf("invalid plugin name %q: must contain only a-z, A-Z, 0-9, _ and -", m.Name)
 	}
 	m.Usage = sanitizeString(m.Usage)
 

internal/plugin/metadata_v1.go

@@ -47,8 +47,11 @@ type MetadataV1 struct {
 }
 
 func (m *MetadataV1) Validate() error {
+	if m.Name == "" {
+		return fmt.Errorf("missing plugin `name`")
+	}
 	if !validPluginName.MatchString(m.Name) {
-		return fmt.Errorf("invalid plugin `name`")
+		return fmt.Errorf("invalid plugin `name` %q: must contain only a-z, A-Z, 0-9, _ and -", m.Name)
 	}
 
 	if m.APIVersion != "v1" {