pkg/types: modify LoadArgs to return a named error when an unmarshalable condition...

diff --git a/pkg/types/args.go b/pkg/types/args.go
index e87c6b6..bd8640f 100644 (file)
--- a/pkg/types/args.go
+++ b/pkg/types/args.go
@@ -63,6 +63,12 @@ func GetKeyField(keyString string, v reflect.Value) reflect.Value {
        return v.Elem().FieldByName(keyString)
 }
 
+// UnmarshalableArgsError is used to indicate error unmarshalling args
+// from the args-string in the form "K=V;K2=V2;..."
+type UnmarshalableArgsError struct {
+       error
+}
+
 // LoadArgs parses args from a string in the form "K=V;K2=V2;..."
 func LoadArgs(args string, container interface{}) error {
        if args == "" {
@@ -88,7 +94,9 @@ func LoadArgs(args string, container interface{}) error {
                keyFieldIface := keyField.Addr().Interface()
                u, ok := keyFieldIface.(encoding.TextUnmarshaler)
                if !ok {
-                       return fmt.Errorf("ARGS: '%s' cannot be unmarshalled from textual form for pair %q", keyField, pair)
+                       return UnmarshalableArgsError{fmt.Errorf(
+                               "ARGS: cannot unmarshal into field '%s' - type '%s' does not implement encoding.TextUnmarshaler",
+                               keyString, reflect.TypeOf(keyFieldIface))}
                }
                err := u.UnmarshalText([]byte(valueString))
                if err != nil {