Config UI: add /config/auth verification endpoint (#25433)

plugin/auth/config.go

@@ -5,12 +5,9 @@ import (
 	"fmt"
 	"strings"
 
-	reg "github.com/evcc-io/evcc/util/registry"
 	"golang.org/x/oauth2"
 )
 
-var registry = reg.New[oauth2.TokenSource]("auth")
-
 // NewFromConfig creates auth from configuration
 func NewFromConfig(ctx context.Context, typ string, other map[string]any) (oauth2.TokenSource, error) {
 	factory, err := registry.Get(strings.ToLower(typ))

plugin/auth/demo.go

@@ -0,0 +1,75 @@
+package auth
+
+import (
+	"context"
+	"net/url"
+	"time"
+
+	"github.com/evcc-io/evcc/api"
+	"github.com/evcc-io/evcc/server/providerauth"
+	"golang.org/x/oauth2"
+)
+
+func init() {
+	registry.AddCtx("demo", NewDemoFromConfig)
+}
+
+type demo struct {
+	token *oauth2.Token
+}
+
+var demoInstance *demo
+
+func NewDemoFromConfig(_ context.Context, _ map[string]any) (oauth2.TokenSource, error) {
+	return NewDemo()
+}
+
+func NewDemo() (oauth2.TokenSource, error) {
+	// reuse instance (similar to oauth.go getInstance pattern)
+	if demoInstance != nil {
+		return demoInstance, nil
+	}
+
+	demoInstance = new(demo)
+
+	if _, err := providerauth.Register("demo", demoInstance); err != nil {
+		return nil, err
+	}
+
+	return demoInstance, nil
+}
+
+func (o *demo) Token() (*oauth2.Token, error) {
+	if o.token == nil {
+		return nil, api.LoginRequiredError("demo")
+	}
+	return o.token, nil
+}
+
+func (o *demo) Login(_ string) (string, error) {
+	// for demo, immediately authenticate without requiring external flow
+	o.token = &oauth2.Token{
+		AccessToken: "demo-token",
+		Expiry:      time.Now().Add(24 * time.Hour),
+	}
+	// TODO use network settings after https://github.com/evcc-io/evcc/pull/25141
+	return "http://localhost:7070/providerauth/callback", nil
+}
+
+func (o *demo) Logout() error {
+	o.token = nil
+	return nil
+}
+
+func (o *demo) HandleCallback(params url.Values) error {
+	// no-op: token already set in Login()
+	return nil
+}
+
+func (o *demo) Authenticated() bool {
+	return o.token != nil
+}
+
+func (o *demo) DisplayName() string {
+	return "demo"
+}

plugin/auth/registry.go

@@ -0,0 +1,12 @@
+package auth
+
+import (
+	reg "github.com/evcc-io/evcc/util/registry"
+	"golang.org/x/oauth2"
+)
+
+var registry = reg.New[oauth2.TokenSource]("auth")
+
+func Register(typ string, fun func(map[string]any) (oauth2.TokenSource, error)) {
+	registry.Add(typ, fun)
+}