Read a model reply through the text property, not the deprecated call

langchain deprecated calling AIMessage.text as a method; it still returns the
right value, so nothing failed and nothing warned loudly enough to notice. The
AI widget had no tests at all, which is why this sat unseen through a langchain
upgrade.

The reply path now has its own tests, including one that records warnings rather
than raising them: call_ai_model catches every exception and answers with a
message box, so a raised warning would be swallowed there instead of failing.
Confirmed the test fails on the deprecated form before fixing it.

Author: JE-Chen

architecture_explore.md

@@ -16,7 +16,7 @@ JEditor 是以 PySide6（Qt for Python）寫成的程式碼編輯器，功能涵
 | 語言 / 版本 | Python 3.10+（CI 測 3.10 / 3.11 / 3.12） |
 | UI 框架 | PySide6 6.11.0 + qt-material 主題 |
 | 主要相依 | `jedi`（Python 補全）、`ruff`（診斷）、`yapf` / `pycodestyle`（格式化與檢查）、`gitpython`、`watchdog`、`qtconsole` + `IPython`、`langchain_openai` + `langchain_core`、`frontengine` |
-| 測試 | pytest + pytest-qt，88 個測試檔、約 13,400 行 |
+| 測試 | pytest + pytest-qt，89 個測試檔、約 13,450 行 |
 | 靜態分析 | ruff、SonarCloud（`sonar.sources=je_editor`）、Codacy、bandit |
 
 ### 各套件規模
@@ -69,7 +69,7 @@ JEditor 是以 PySide6（Qt for Python）寫成的程式碼編輯器，功能涵
 **設計慣例**：幾乎每個功能都拆成「純邏輯 + Qt 整合層」兩塊。
 例如折疊 = `utils/code_folding/fold_regions.py`（算區塊）+ `pyside_ui/code/folding/folding_manager.py`（藏行、重畫）；
 書籤 = `utils/bookmark/bookmark_navigation.py` + `pyside_ui/code/bookmark/bookmark_manager.py`。
-這讓大部分邏輯可以不開視窗就測試，也是 `test/` 能有 88 個測試檔的原因。
+這讓大部分邏輯可以不開視窗就測試，也是 `test/` 能有 89 個測試檔的原因。
 
 ---
 
@@ -478,7 +478,7 @@ qt-material 負責視窗樣式；編輯器自身的顏色（語法高亮、diff
 
 ## 7. 測試與 CI
 
-- `test/` 88 個測試檔、約 13,400 行，與模組大致一對一（`test_fold_regions.py`、`test_shortcut_registry.py`…）。
+- `test/` 89 個測試檔、約 13,450 行，與模組大致一對一（`test_fold_regions.py`、`test_shortcut_registry.py`…）。
 - `conftest.py` 提供 session 級 `qapp`、`tmp_dir`、`tmp_file`，以及 autouse 的「等工具列背景執行緒結束」fixture；
   `collect_ignore_glob` 排除會真的開視窗的 `start_qt_ui.py` / `extend_test.py`。
 - `pyproject.toml` 設定 `testpaths = ["test"]`、`qt_api = "pyside6"`；bandit 排除測試目錄（pytest 慣用 `assert`）。

je_editor/pyside_ui/main_ui/ai_widget/langchain_interface.py

@@ -62,8 +62,10 @@ def call_ai_model(self, prompt: str) -> str | None:
         """
         message = None
         try:
-            # 呼叫 AI 並取得回覆 / Invoke AI and get response
-            message = self.chat_ai.invoke(prompt).text()
+            # 呼叫 AI 並取得回覆；``text`` 是屬性，當成方法呼叫已被 langchain 標為棄用
+            # Invoke AI and get response. ``text`` is a property: calling it as a
+            # method is deprecated in langchain and will stop working.
+            message = self.chat_ai.invoke(prompt).text
 
             # 嘗試過濾掉 <think> 標籤前的內容，只保留主要回覆
             # Try to filter out content before </think>, keep only main response

test/test_langchain_interface.py

@@ -0,0 +1,94 @@
+"""Tests for how the AI widget reads a reply out of a langchain message."""
+from __future__ import annotations
+
+import os
+import warnings
+
+import pytest
+from langchain_core.messages import AIMessage
+
+from je_editor.pyside_ui.main_ui.ai_widget.langchain_interface import LangChainInterface
+
+
+class FakeChat:
+    """Stand in for ChatOpenAI, returning a real AIMessage without any network."""
+
+    def __init__(self, content: str) -> None:
+        self._content = content
+        self.prompts: list[str] = []
+
+    def invoke(self, prompt: str) -> AIMessage:
+        self.prompts.append(prompt)
+        return AIMessage(content=self._content)
+
+
+@pytest.fixture(autouse=True)
+def _restore_openai_environment():
+    """The interface writes its settings into os.environ; put them back afterwards."""
+    keys = ("OPENAI_BASE_URL", "OPENAI_API_KEY", "CHAT_MODEL")
+    saved = {key: os.environ.get(key) for key in keys}
+    yield
+    for key, value in saved.items():
+        if value is None:
+            os.environ.pop(key, None)
+        else:
+            os.environ[key] = value
+
+
+def build_interface(content: str) -> LangChainInterface:
+    """An interface whose model is replaced by a fake that answers with ``content``."""
+    interface = LangChainInterface(
+        main_window=None,
+        prompt_template="You are a {role}.",
+        base_url="https://example.invalid/v1",
+        api_key="not-a-real-key",
+        chat_model="gpt-4o-mini",
+    )
+    interface.chat_ai = FakeChat(content)
+    return interface
+
+
+class TestReadingTheReply:
+    def test_a_plain_reply_comes_back_unchanged(self):
+        assert build_interface("hello there").call_ai_model("hi") == "hello there"
+
+    def test_the_prompt_reaches_the_model(self):
+        interface = build_interface("anything")
+        interface.call_ai_model("what is 2 + 2?")
+        assert interface.chat_ai.prompts == ["what is 2 + 2?"]
+
+    def test_an_empty_reply_stays_empty(self):
+        assert build_interface("").call_ai_model("hi") == ""
+
+    def test_reading_the_text_warns_of_nothing_deprecated(self):
+        """
+        ``text`` is a property; calling it as a method is deprecated upstream and
+        will eventually stop working. Nothing else here would notice, because the
+        deprecated form still returns the right value.
+
+        The warnings are recorded rather than raised: ``call_ai_model`` catches
+        every exception and answers with a message box, so a raised warning would
+        be swallowed there instead of failing the test.
+        """
+        interface = build_interface("hello there")
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always")
+            assert interface.call_ai_model("hi") == "hello there"
+        deprecated = [
+            str(warning.message) for warning in caught
+            if issubclass(warning.category, DeprecationWarning)
+        ]
+        assert not deprecated, deprecated
+
+
+class TestStrippingTheThinkingBlock:
+    def test_content_before_the_closing_tag_is_dropped(self):
+        interface = build_interface("<think>internal reasoning</think>\n  the answer  ")
+        assert interface.call_ai_model("hi") == "the answer"
+
+    def test_a_reply_without_the_tag_is_left_alone(self):
+        assert build_interface("just the answer").call_ai_model("hi") == "just the answer"
+
+    def test_only_the_first_closing_tag_starts_the_answer(self):
+        interface = build_interface("<think>a</think>first</think>second")
+        assert interface.call_ai_model("hi") == "first</think>second"