ConfigV2: Replace list params - fix #108 (#113)

* Fix #108: Version 2 configs override list params

* Version compare must be equals or greater

Author: jkellerer

config/config.go

@@ -56,6 +56,12 @@ var (
 		confidentialValueDecoder(),
 	))
 
+	configOptionV2 = viper.DecodeHook(mapstructure.ComposeDecodeHookFunc(
+		mapstructure.StringToTimeDurationHookFunc(),
+		confidentialValueDecoder(),
+		forceSliceReplacementHookFunc(),
+	))
+
 	configOptionHCL = viper.DecodeHook(mapstructure.ComposeDecodeHookFunc(
 		mapstructure.StringToTimeDurationHookFunc(),
 		confidentialValueDecoder(),
@@ -585,10 +591,28 @@ func (c *Config) getSchedule(key string) (Schedule, error) {
 func (c *Config) unmarshalKey(key string, rawVal interface{}) error {
 	if c.format == "hcl" {
 		return c.viper.UnmarshalKey(key, rawVal, configOptionHCL)
+	} else if c.GetVersion() >= Version02 {
+		return c.viper.UnmarshalKey(key, rawVal, configOptionV2)
 	}
 	return c.viper.UnmarshalKey(key, rawVal, configOption)
 }
 
+// forceSliceReplacementHookFunc clears the target slice before assigning a new value
+func forceSliceReplacementHookFunc() mapstructure.DecodeHookFuncValue {
+	return func(from reflect.Value, to reflect.Value) (interface{}, error) {
+		if kind := from.Type().Kind(); (kind == reflect.Slice || kind == reflect.Array || kind == reflect.String) && from.Len() > 0 {
+			if kind = to.Type().Kind(); (kind == reflect.Slice || kind == reflect.Array) && to.Len() > 0 {
+				if kind == reflect.Slice {
+					to.SetLen(0)
+				} else {
+					to.Set(to.Slice(0, 0))
+				}
+			}
+		}
+		return from.Interface(), nil
+	}
+}
+
 // sliceOfMapsToMapHookFunc merges a slice of maps to a map
 func sliceOfMapsToMapHookFunc() mapstructure.DecodeHookFunc {
 	return func(from reflect.Type, to reflect.Type, data interface{}) (interface{}, error) {

config/config_test.go

@@ -444,3 +444,41 @@ profile:
 
 	assert.Equal(t, []string{"daily"}, schedules[0].Schedules())
 }
+
+func TestRegressionInheritanceListMerging(t *testing.T) {
+	load := func(content string) *Config {
+		buffer := bytes.NewBufferString(content)
+		cfg, err := Load(buffer, FormatYAML)
+		require.NoError(t, err)
+		require.NotNil(t, cfg)
+		return cfg
+	}
+
+	t.Run("Version1", func(t *testing.T) {
+		config := load(`---
+base:
+  run-before: ["base-first", "base-second", "base-third"]
+profile:
+  inherit: base
+  run-before: [null, "profile-before"]
+`)
+		profile, err := config.GetProfile("profile")
+		require.NoError(t, err)
+		assert.Equal(t, []string{"base-first", "profile-before", "base-third"}, profile.RunBefore)
+	})
+
+	t.Run("Version2", func(t *testing.T) {
+		config := load(`---
+version: 2
+profiles:
+  base:
+    run-before: ["base-first", "base-second", "base-third"]
+  profile:
+    inherit: base
+    run-before: [null, "profile-before"]
+`)
+		profile, err := config.GetProfile("profile")
+		require.NoError(t, err)
+		assert.Equal(t, []string{"", "profile-before"}, profile.RunBefore)
+	})
+}