fix(linkai_voice): return an ERROR reply on ASR/TTS failure instead of None

LinkAI was the only voice provider that returned None on a failed
transcription or synthesis (voice/linkai/linkai_voice.py, 4 sites).
Every sibling (ali, openai, mimo) returns Reply(ReplyType.ERROR, ...),
so the user hears/sees a failure message. A None bubbles up through
bridge.fetch_voice_to_text with no Reply at all and the turn goes silent
(or the caller dereferences a None reply).

Replace the four `return None` with ReplyType.ERROR replies, reusing the
same Chinese strings the other providers use ("抱歉，语音识别失败" /
"抱歉，语音合成失败").

Tests: the four failure exits (ASR/TTS, HTTP error / exception) now
return an ERROR reply instead of None.

tests/test_linkai_voice_error_reply.py

@@ -0,0 +1,79 @@
+# encoding:utf-8
+"""
+Regression tests for ``voice/linkai/linkai_voice.py``.
+
+When LinkAI ASR/TTS fails, the old code returned ``None``. Every sibling
+provider (ali, openai, mimo) returns a ``Reply(ReplyType.ERROR, ...)``
+instead, so the user gets a failure message; LinkAI's ``None`` means the
+bridge returns no Reply at all (``bridge/bridge.py::fetch_voice_to_text``)
+and the turn goes silent. These tests assert the four failure exits now
+produce an ERROR reply.
+"""
+import os
+import sys
+import unittest
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+
+from bridge.reply import ReplyType
+from voice.linkai.linkai_voice import LinkAIVoice
+
+
+class TestLinkAIVoiceErrorReply(unittest.TestCase):
+    def _voice(self):
+        return LinkAIVoice()
+
+    def _audio(self):
+        p = Path(__file__).with_suffix(".mp3")
+        p.write_bytes(b"fake-audio-bytes")
+        return p
+
+    def test_voiceToText_http_error_returns_error_reply(self):
+        v = self._voice()
+        resp = MagicMock()
+        resp.status_code = 500
+        resp.json.return_value = {"message": "boom"}
+        audio = self._audio()
+        with patch("voice.linkai.linkai_voice.requests.post", return_value=resp):
+            reply = v.voiceToText(str(audio))
+        audio.unlink()
+        self.assertIsNotNone(reply)
+        self.assertEqual(reply.type, ReplyType.ERROR)
+        self.assertIn("识别", reply.content)
+
+    def test_voiceToText_exception_returns_error_reply(self):
+        v = self._voice()
+        audio = self._audio()
+        with patch(
+            "voice.linkai.linkai_voice.requests.post", side_effect=RuntimeError("net down")
+        ):
+            reply = v.voiceToText(str(audio))
+        audio.unlink()
+        self.assertIsNotNone(reply)
+        self.assertEqual(reply.type, ReplyType.ERROR)
+
+    def test_textToVoice_http_error_returns_error_reply(self):
+        v = self._voice()
+        resp = MagicMock()
+        resp.status_code = 500
+        resp.json.return_value = {"message": "boom"}
+        with patch("voice.linkai.linkai_voice.requests.post", return_value=resp):
+            reply = v.textToVoice("hello")
+        self.assertIsNotNone(reply)
+        self.assertEqual(reply.type, ReplyType.ERROR)
+        self.assertIn("合成", reply.content)
+
+    def test_textToVoice_exception_returns_error_reply(self):
+        v = self._voice()
+        with patch(
+            "voice.linkai.linkai_voice.requests.post", side_effect=RuntimeError("net down")
+        ):
+            reply = v.textToVoice("hello")
+        self.assertIsNotNone(reply)
+        self.assertEqual(reply.type, ReplyType.ERROR)
+
+
+if __name__ == "__main__":
+    unittest.main()

voice/linkai/linkai_voice.py

@@ -56,13 +56,13 @@ class LinkAIVoice(Voice):
                 except Exception:
                     pass
                 logger.error(f"[LinkVoice] voiceToText error, status_code={res.status_code}, msg={msg}")
-                return None
+                return Reply(ReplyType.ERROR, "抱歉，语音识别失败")
             text = res.json().get("text")
             logger.info(f"[LinkVoice] voiceToText success, text={text}, file name={voice_file}")
             return Reply(ReplyType.TEXT, text)
         except Exception as e:
             logger.error(e)
-            return None
+            return Reply(ReplyType.ERROR, "抱歉，语音识别失败")
 
     def textToVoice(self, text):
         try:
@@ -88,7 +88,7 @@ class LinkAIVoice(Voice):
                 except Exception:
                     pass
                 logger.error(f"[LinkVoice] textToVoice error, status_code={res.status_code}, msg={msg}")
-                return None
+                return Reply(ReplyType.ERROR, "抱歉，语音合成失败")
             tmp_file_name = TmpDir().path() + datetime.datetime.now().strftime('%Y%m%d%H%M%S') + str(random.randint(0, 1000)) + ".mp3"
             with open(tmp_file_name, 'wb') as f:
                 f.write(res.content)
@@ -96,4 +96,4 @@ class LinkAIVoice(Voice):
             return Reply(ReplyType.VOICE, tmp_file_name)
         except Exception as e:
             logger.error(e)
-            return None
+            return Reply(ReplyType.ERROR, "抱歉，语音合成失败")