Config UI: fix editing existing OAuth devices (#28012)

server/http.go

@@ -279,6 +279,7 @@ func (s *HTTPd) RegisterSystemHandler(site *core.Site, pub publisher, cache *uti
 
 		routes := map[string]route{
 			"auth":               {"POST", "/auth", authHandler},
+			"authmerged":         {"POST", "/auth/{class:[a-z]+}/merge/{id:[0-9.]+}", authHandler},
 			"templates":          {"GET", "/templates/{class:[a-z]+}", templatesHandler},
 			"products":           {"GET", "/products/{class:[a-z]+}", productsHandler},
 			"devices":            {"GET", "/devices/{class:[a-z]+}", devicesConfigHandler},

server/http_config_helper.go

@@ -107,6 +107,7 @@ func templateForConfig(class templates.Class, conf map[string]any) (templates.Te
 	return templates.ByName(class, typ)
 }
 
+// filterValidTemplateParams removes all configuration properties that are not part of the template definition
 func filterValidTemplateParams(tmpl *templates.Template, conf map[string]any) map[string]any {
 	res := make(map[string]any)
 
@@ -169,6 +170,32 @@ func mergeMasked(class templates.Class, conf, old map[string]any) (map[string]an
 	})
 }
 
+// deviceOther looks up a stored device's `Other` config by class and id.
+func deviceOther(class templates.Class, id int) (map[string]any, error) {
+	name := config.NameForID(id)
+	switch class {
+	case templates.Charger:
+		return deviceOtherFromHandler(name, config.Chargers())
+	case templates.Meter:
+		return deviceOtherFromHandler(name, config.Meters())
+	case templates.Vehicle:
+		return deviceOtherFromHandler(name, config.Vehicles())
+	case templates.Tariff:
+		return deviceOtherFromHandler(name, config.Tariffs())
+	case templates.Messenger:
+		return deviceOtherFromHandler(name, config.Messengers())
+	}
+	return nil, errors.New("unsupported class: " + class.String())
+}
+
+func deviceOtherFromHandler[T any](name string, h config.Handler[T]) (map[string]any, error) {
+	dev, err := h.ByName(name)
+	if err != nil {
+		return nil, err
+	}
+	return dev.Config().Other, nil
+}
+
 func startDeviceTimeout() (context.Context, context.CancelFunc, chan struct{}) {
 	done := make(chan struct{})
 	ctx, cancel := context.WithCancel(context.Background())

server/http_config_metadata_handler.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"net/http"
 	"slices"
+	"strconv"
 	"strings"
 
 	"github.com/evcc-io/evcc/plugin/auth"
@@ -42,6 +43,38 @@ func authHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// when editing existing device, merge masked values with stored config
+	if vars := mux.Vars(r); vars["class"] != "" && vars["id"] != "" {
+		id, err := strconv.Atoi(vars["id"])
+		if err != nil {
+			jsonError(w, http.StatusBadRequest, err)
+			return
+		}
+
+		class, err := templates.ClassString(vars["class"])
+		if err != nil {
+			jsonError(w, http.StatusBadRequest, err)
+			return
+		}
+
+		old, err := deviceOther(class, id)
+		if err != nil {
+			jsonError(w, http.StatusBadRequest, err)
+			return
+		}
+
+		merged, err := mergeMasked(class, cc.Other, old)
+		if err != nil {
+			jsonError(w, http.StatusBadRequest, err)
+			return
+		}
+
+		cc.Other = merged
+	}
+
+	// template is only needed by mergeMasked above; the auth decoder is strict
+	delete(cc.Other, typeTemplate)
+
 	ts, err := auth.NewFromConfig(context.Background(), cc.Type, cc.Other)
 	if err != nil {
 		jsonError(w, http.StatusBadRequest, err)