VSCode全容器化Python开发环境调试需两次启动的问题求助

TL;DR：为何需要启动两次调试，才能让VSCode调试器成功连接到容器内的Python服务？

我正尝试在VSCode中搭建基于容器的Python开发环境，希望直接复用生产环境的容器配置，避免在本地处理Python版本、虚拟环境等问题。我使用VSCode自动生成的部分配置文件，结合教程调整后环境勉强可用，但存在严重问题：必须点击两次「开始调试（F5）」，调试器才能成功连接到容器。

这只是测试项目的情况，在我的实际Python项目中，调试器甚至完全无法连接。我认为当前配置仍有优化空间，特此寻求帮助。以下是我的配置文件：

Dockerfile:

# For more information, please refer to https://aka.ms/vscode-docker-python
FROM python:3.10-slim

# Keeps Python from generating .pyc files in the container
ENV PYTHONDONTWRITEBYTECODE=1

# Turns off buffering for easier container logging
ENV PYTHONUNBUFFERED=1

# Install pip requirements
COPY requirements.txt .
RUN python -m pip install --upgrade pip && \
    python -m pip install -r requirements.txt

WORKDIR /app
COPY . /app

# Creates a non-root user with an explicit UID and adds permission to access the /app folder
# For more info, please refer to https://aka.ms/vscode-docker-python-configure-containers
RUN adduser -u 5678 --disabled-password --gecos "" appuser && chown -R appuser /app
USER appuser

# During debugging, this entry point will be overridden. For more information, please refer to https://aka.ms/vscode-docker-python-debug
CMD ["python", "-m", "testproj"]

EXPOSE 80

docker-compose.debug.yml:

version: '3.4'

services:
  testtasks:
    image: testtasks
    build:
      context: .
      dockerfile: ./Dockerfile
    command:
      [
        "sh",
        "-c",
        "pip install debugpy -t /tmp && python /tmp/debugpy --wait-for-client --listen 0.0.0.0:5678 -m uvicorn testproj.testproj:app --host 0.0.0.0 --port 80 --reload"
      ]
    ports:
      - 80:80
      - 5678:5678
    volumes:
      - ${PWD}:/app

requirements.txt:

fastapi
uvicorn

testproj/__main__.py:

import uvicorn
uvicorn.run("testproj.testproj:app", host="0.0.0.0", port=80)

testproj/testproj.py:

from typing import Union
from fastapi import FastAPI
app = FastAPI()

@app.get("/")
async def read_root():
    return {"Hello": "World"}

.vscode/tasks.json:

{
    "version": "2.0.0",
    "tasks": [
        {
            "type": "docker-build",
            "label": "docker-build",
            "platform": "python",
            "dockerBuild": {
                "tag": "testtasks:latest",
                "dockerfile": "${workspaceFolder}/Dockerfile",
                "context": "${workspaceFolder}",
                "pull": true
            }
        },
        {
            "label": "Run compose up",
            "type": "docker-compose",
            "dockerCompose": {
                "up": {
                    "detached": true,
                    "build": true
                },
                "files": [
                    "${workspaceFolder}/docker-compose.debug.yml"
                ]
            }
        },
        {
            "label": "Run compose down",
            "type": "docker-compose",
            "dockerCompose": {
                "down": {},
                "files": [
                    "${workspaceFolder}/docker-compose.debug.yml"
                ]
            }
        }
    ]
}

.vscode/launch.json:

{
    "configurations": [
        {
            "name": "Python: Remote Attach",
            "type": "python",
            "request": "attach",
            "connect": {
                "host": "localhost",
                "port": 5678
            },
            "pathMappings": [
                {
                    "localRoot": "${workspaceFolder}",
                    "remoteRoot": "/app"
                }
            ],
            "preLaunchTask": "Run compose up",
            "postDebugTask": "Run compose down",
            "justMyCode": true
        }
    ]
}

操作现象：第一次点击左上角绿色运行按钮会启动容器，但调试器无法连接；第二次点击调试器成功连接，底部状态栏变为红色，停止功能正常。

内容的提问来源于stack exchange，提问作者mcnesium