Fix #1732 AutomaticEnv does not override Unmarshaled config slice values

viper.go

@@ -689,6 +689,59 @@ func (v *Viper) searchMap(source map[string]any, path []string) any {
 	return nil
 }
 
+// searchMapWithAliases recursively searches for slice field in source map and
+// replace them with the environment variable value if it exists.
+//
+// Returns replaced values.
+func (v *Viper) searchAndReplaceSliceValueWithEnv(source any, envKey string) any {
+	switch sourceValue := source.(type) {
+	case []any:
+		var newSliceValues []any
+		for i, sliceValue := range sourceValue {
+			envKey := envKey + v.keyDelim + strconv.Itoa(i)
+			switch existingValue := sliceValue.(type) {
+			case map[string]any:
+				newVal := v.searchAndReplaceSliceValueWithEnv(existingValue, envKey)
+				newSliceValues = append(newSliceValues, newVal)
+
+			default:
+				if newVal, ok := v.getEnv(v.mergeWithEnvPrefix(envKey)); ok {
+					newSliceValues = append(newSliceValues, newVal)
+				} else {
+					newSliceValues = append(newSliceValues, existingValue)
+				}
+			}
+		}
+		return newSliceValues
+
+	case map[string]any:
+		var newMapValues map[string]any = make(map[string]any)
+		for key, mapValue := range sourceValue {
+			envKey := envKey + v.keyDelim + key
+			switch existingValue := mapValue.(type) {
+			case map[string]any:
+				newVal := v.searchAndReplaceSliceValueWithEnv(existingValue, envKey)
+				newMapValues[key] = newVal
+
+			default:
+				if newVal, ok := v.getEnv(v.mergeWithEnvPrefix(envKey)); ok {
+					newMapValues[key] = newVal
+				} else {
+					newMapValues[key] = existingValue
+				}
+			}
+		}
+		return newMapValues
+
+	default:
+		if newVal, ok := v.getEnv(v.mergeWithEnvPrefix(envKey)); ok {
+			return newVal
+		} else {
+			return source
+		}
+	}
+}
+
 // searchIndexableWithPathPrefixes recursively searches for a value for path in source map/slice.
 //
 // While searchMap() considers each path element as a single map key or slice index, this
@@ -906,6 +959,11 @@ func (v *Viper) Get(key string) any {
 		return nil
 	}
 
+	// Check for Env override again, to handle slices
+	if v.automaticEnvApplied {
+		val = v.searchAndReplaceSliceValueWithEnv(val, lcaseKey)
+	}
+
 	if v.typeByDefValue {
 		// TODO(bep) this branch isn't covered by a single test.
 		valType := val

viper_test.go

@@ -2606,6 +2606,85 @@ func TestSliceIndexAccess(t *testing.T) {
 	assert.Equal(t, "Static", v.GetString("tv.0.episodes.1.2"))
 }
 
+var yamlSimpleSlice = []byte(`
+name: Steve
+port: 8080
+auth:
+  secret: 88888-88888
+modes:
+  - 1
+  - 2
+  - 3
+clients:
+  - name: foo
+  - name: bar
+proxy:
+  clients:
+  - name: proxy_foo
+  - name: proxy_bar
+  - name: proxy_baz
+`)
+
+func TestSliceIndexAutomaticEnv(t *testing.T) {
+	v.SetConfigType("yaml")
+	r := strings.NewReader(string(yamlSimpleSlice))
+
+	type ClientConfig struct {
+		Name string
+	}
+
+	type AuthConfig struct {
+		Secret string
+	}
+
+	type ProxyConfig struct {
+		Clients []ClientConfig
+	}
+
+	type Configuration struct {
+		Port    int
+		Name    string
+		Auth    AuthConfig
+		Modes   []int
+		Clients []ClientConfig
+		Proxy   ProxyConfig
+	}
+
+	// Read yaml as default value
+	err := v.unmarshalReader(r, v.config)
+	require.NoError(t, err)
+
+	assert.Equal(t, "Steve", v.GetString("name"))
+	assert.Equal(t, 8080, v.GetInt("port"))
+	assert.Equal(t, "88888-88888", v.GetString("auth.secret"))
+	assert.Equal(t, "foo", v.GetString("clients.0.name"))
+	assert.Equal(t, "bar", v.GetString("clients.1.name"))
+	assert.Equal(t, "proxy_foo", v.GetString("proxy.clients.0.name"))
+	assert.Equal(t, []int{1, 2, 3}, v.GetIntSlice("modes"))
+
+	// Override with env variable
+	t.Setenv("NAME", "Steven")
+	t.Setenv("AUTH_SECRET", "99999-99999")
+	t.Setenv("MODES_2", "300")
+	t.Setenv("CLIENTS_1_NAME", "baz")
+	t.Setenv("PROXY_CLIENTS_0_NAME", "ProxyFoo")
+
+	SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
+	AutomaticEnv()
+
+	// Unmarshal into struct
+	var config Configuration
+	v.Unmarshal(&config)
+
+	assert.Equal(t, "Steven", config.Name)
+	assert.Equal(t, 8080, config.Port)
+	assert.Equal(t, "99999-99999", config.Auth.Secret)
+	assert.Equal(t, []int{1, 2, 300}, config.Modes)
+	assert.Equal(t, "foo", config.Clients[0].Name)
+	assert.Equal(t, "baz", config.Clients[1].Name)
+	assert.Equal(t, "ProxyFoo", config.Proxy.Clients[0].Name)
+}
+
 func TestIsPathShadowedInFlatMap(t *testing.T) {
 	v := New()