fix: propagate QR output failures

auth.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"net/http"
 	"net/url"
 	"os"
@@ -251,6 +252,19 @@ type longPollData struct {
 
 type stringOrNumber string
 
+type recordingWriter struct {
+	w   io.Writer
+	err error
+}
+
+func (writer *recordingWriter) Write(payload []byte) (int, error) {
+	written, err := writer.w.Write(payload)
+	if err != nil && writer.err == nil {
+		writer.err = err
+	}
+	return written, err
+}
+
 func (value *stringOrNumber) UnmarshalJSON(payload []byte) error {
 	decoded, err := decodeStringOrNumber(payload)
 	if err != nil {
@@ -282,10 +296,18 @@ func (client *Client) Login(ctx context.Context) (AuthData, error) {
 		if _, err := qr.Encode(loginData.LoginURL, qr.L); err != nil {
 			return AuthData{}, fmt.Errorf("encode login QR code: %w", err)
 		}
-		fmt.Fprintf(client.qrWriter, "请使用米家APP扫描下方二维码\n%s\n", loginData.LoginURL)
-		qrterminal.GenerateHalfBlock(loginData.LoginURL, qrterminal.L, client.qrWriter)
+		writer := &recordingWriter{w: client.qrWriter}
+		if _, err := fmt.Fprintf(writer, "请使用米家APP扫描下方二维码\n%s\n", loginData.LoginURL); err != nil {
+			return AuthData{}, fmt.Errorf("write QR login output: %w", err)
+		}
+		qrterminal.GenerateHalfBlock(loginData.LoginURL, qrterminal.L, writer)
+		if writer.err != nil {
+			return AuthData{}, fmt.Errorf("write QR login output: %w", writer.err)
+		}
 		if loginData.QR != "" {
-			fmt.Fprintf(client.qrWriter, "二维码图片: %s\n", loginData.QR)
+			if _, err := fmt.Fprintf(writer, "二维码图片: %s\n", loginData.QR); err != nil {
+				return AuthData{}, fmt.Errorf("write QR login output: %w", err)
+			}
 		}
 	}
 	return client.completeQRLogin(ctx, loginData)