Fix rendering nil interfaces as "<nil>" string

util/decoder_test.go

@@ -0,0 +1,36 @@
+package util
+
+import (
+	"testing"
+
+	"github.com/mitchellh/mapstructure"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDecodeNil(t *testing.T) {
+	var dst struct {
+		User, Password string
+	}
+
+	decoderConfig := &mapstructure.DecoderConfig{
+		Result:           &dst,
+		ErrorUnused:      true,
+		WeaklyTypedInput: true,
+		DecodeHook: mapstructure.ComposeDecodeHookFunc(
+			mapstructure.StringToTimeDurationHookFunc(),
+			mapstructure.TextUnmarshallerHookFunc(),
+		),
+	}
+
+	decoder, err := mapstructure.NewDecoder(decoderConfig)
+	assert.NoError(t, err)
+
+	err = decoder.Decode(map[string]any{
+		"user": nil,
+	})
+	assert.NoError(t, err)
+
+	assert.Equal(t, struct {
+		User, Password string
+	}{}, dst)
+}

util/templates/template.go

@@ -323,7 +323,12 @@ func (t *Template) RenderResult(renderMode string, other map[string]interface{})
 
 		default:
 			if res[out] == nil || res[out].(string) == "" {
-				res[out] = yamlQuote(fmt.Sprintf("%v", val))
+				// prevent rendering nil interfaces as "<nil>" string
+				var s string
+				if val != nil {
+					s = yamlQuote(fmt.Sprintf("%v", val))
+				}
+				res[out] = s
 			}
 		}
 	}