Config UI: add provider auth subject to login errors (#25342)

util/error.go

@@ -0,0 +1,36 @@
+package util
+
+import (
+	"errors"
+
+	"github.com/evcc-io/evcc/api"
+	"go.yaml.in/yaml/v4"
+)
+
+// ErrorAsJson returns an error as json-formattable struct
+func ErrorAsJson(err error) any {
+	res := struct {
+		Error         string `json:"error"`
+		Line          int    `json:"line,omitempty"`
+		LoginRequired string `json:"loginRequired,omitempty"`
+	}{
+		Error: err.Error(),
+	}
+
+	if ae := new(api.ErrLoginRequired); errors.As(err, &ae) {
+		res.LoginRequired = ae.ProviderAuth
+	}
+
+	var (
+		ype *yaml.ParserError
+		yue *yaml.UnmarshalError
+	)
+	switch {
+	case errors.As(err, &ype):
+		res.Line = ype.Line
+	case errors.As(err, &yue):
+		res.Line = yue.Line
+	}
+
+	return res
+}