From 85c7126bbd77ee464c557874a002d9ad5ba044aa Mon Sep 17 00:00:00 2001
From: andig <cpuidle@gmx.de>
Date: Thu, 2 Mar 2023 15:51:19 +0100
Subject: [PATCH] Fix rendering nil interfaces as "<nil>" string

---
 util/decoder_test.go       | 36 ++++++++++++++++++++++++++++++++++++
 util/templates/template.go |  7 ++++++-
 2 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 util/decoder_test.go

diff --git a/util/decoder_test.go b/util/decoder_test.go
new file mode 100644
index 000000000..b78eb42c5
--- /dev/null
+++ b/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)
+}
diff --git a/util/templates/template.go b/util/templates/template.go
index 2a9230680..1982e7b0c 100644
--- a/util/templates/template.go
+++ b/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
 			}
 		}
 	}