GitHub Actions报set-output弃用警告，但未使用该命令的解决咨询

警告并非来自你编写的步骤代码，而是你配置中使用的第三方Action（如actions/setup-python@v3或codecov/codecov-action@v3）内部仍在调用已弃用的set-output命令。GitHub会检测所有执行步骤（包括第三方Action的内部逻辑）中的旧命令并发出警告。

• 升级第三方Action到最新稳定版
  第三方Action的维护者通常会跟进GitHub的规范更新，替换配置中Action的版本号即可消除警告：

  • 将actions/checkout@v3升级为actions/checkout@v4
  • 将actions/setup-python@v3升级为actions/setup-python@v4
  • 将codecov/codecov-action@v3升级为codecov/codecov-action@v4

• 修改后的完整配置

name: Python application

on:
  push:
    branches: [ "main" ]
  pull_request:
    branches: [ "main" ]

permissions:
  contents: read

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
    - name: Check out
      uses: actions/checkout@v4

    - name: Set up Python 3.10
      uses: actions/setup-python@v4
      with:
        python-version: "3.10"

    - name: Install dependencies
      run: |
        python -m pip install --upgrade pip
        pip install pylint pytest pytest-cov
        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi

    - name: Lint with pylint
      run: |
        pylint src
      continue-on-error: false

    - name: Test with pytest
      run: |
        pytest
        
    - name: pytest coverage
      run: pytest --cov=./ --cov-report=xml:tests/coverage.xml
    - name: Upload coverage to Codecov
      uses: codecov/codecov-action@v4

• 特殊情况处理
  如果升级后仍有警告，说明对应Action的维护者尚未完成适配，此时可暂时忽略警告，等待该Action的后续更新版本即可。

内容的提问来源于stack exchange，提问作者Robert Alexander