VSCode 如何断点调试 uv：`uv run langchain serve` - 前端学 FastAPI 系列

How to debug `uv run ...` python program in VSCode

想要调试下 FastAPI 中 sqlmodel（底层是 sqlalchemy）是如何通过主键 id 获取一个数据库记录的：

@app.get("/heroes/{hero_id}")
def read_hero(hero_id: int, session: SessionDep) -> HeroPublic:
    hero = session.get(Hero, hero_id)

    if not hero:
        raise HTTPException(status_code=404, detail="Hero not found")

    return HeroPublic.model_validate(hero)

今天尝试了很久才成功在 uv run langchain serve 运行的 python 程序中打断点。当然 Trae 等 VSCode IDE 一律可用。

‍ 抄作业

.vscode/launch.json

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": " `uv run langchain serve` debugger",
      "type": "debugpy",
      "request": "launch",
      "program": "${workspaceFolder}/.venv/Scripts/langchain.exe",
      "args": ["serve"],
      "console": "integratedTerminal",
      "justMyCode": false,
      "cwd": "${workspaceFolder}",
      "env": {
        "PYTHONPATH": "${workspaceFolder}"
      }
    }
  ]
}

说明

1. 因为我们想调试包源码，故 "justMyCode": false
2. langchain 位置如何确定？首先进入项目根目录且确保虚拟环境已经启动：

 which langchain 
/f/workspace/github/my-app/.venv/Scripts/langchain

or

 uv run which langchain
/f/workspace/github/my-app/.venv/Scripts/langchain

注意 Windows 需要加 .exe "program": "${workspaceFolder}/.venv/Scripts/langchain.exe", 否则报错：

FileNotFoundError: [Errno 2] No such file or directory: 'F:workspacegithubmy-app.venvScriptslangchain'

开启调试

已 Trae 为例：打断点 → 然后点击左侧 Bug 小虫子 标志 → 下拉框选择 uv run langchain serve debugger → 点击右侧绿色小虫子（Start Debugging）或直接 $F5$ 开启调试，日志如下：

  cd F:\workspace\github\my-app ; /usr/bin/env f:\workspace\github\my-app\.venv\Scripts\python.exe c:\Users\liuchuanzong\.trae-cn\extensions\ms-python.debugpy-2025.18.0-win32-x64\bundled\libs\debugpy\launcher 54274 -- F:\workspace\github\my-app/.venv/Scripts/langchain.exe serve
INFO:     Will watch for changes in these directories: ['F:\workspace\github\my-app']
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [18892] using StatReload
INFO:     Started server process [16184]
INFO:     Waiting for application startup.
INFO:     Application startup complete.

触发

 curl -s http://localhost:8000/heroes/1 | jq

{
  "name": "legend80s",
  "age": null,
  "id": 1
}

可以看到我们的程序断在了我们刚刚打的断点处。

感想

还是 DeepSeek 帮我解决了问题，Kimi 2 胡说八道，社区方案并不可信，uv 官方这个 issue Running uv scripts in debug mode #8558 一直是 open，还在等着 VSCode 官方解决 。