Github Actions缓存Python依赖失效：缓存命中仍重复安装

我在个人仓库中配置了Github Actions以运行Python项目，项目依赖第三方库，直接安装依赖时执行效率正常。但尝试缓存依赖后，每次运行虽显示缓存命中，却仍会重复安装依赖，请问是否遗漏了关键步骤？

提供的Workflow配置：

name: Daily Python Script

on:
  schedule:
    - cron: "0 19 * * *"
  workflow_dispatch: #Manual trigger
  
jobs:
  build:
    runs-on: ubuntu-latest
    
    permissions:
        # Give the default GITHUB_TOKEN write permission to commit and push the
        # added or changed files to the repository.
        contents: write

    steps:
      - name: Set up Python
        uses: actions/setup-python@v4
        with:
          python-version: 3.9

      - name: Update Node.js to v16
        uses: actions/setup-node@v3
        with:
          node-version: 16

      - name: Checkout Code
        uses: actions/checkout@v4

      - name: Restore Cached Dependencies
        uses: actions/cache@v3
        with:
          path: ~/.cache/pip
          key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}
                    
      - name: Debug Cache
        run: |
            echo "Cache hit: ${{ steps.cache-dependencies.outputs.cache-hit }}"
            ls -l ~/.cache/pip

      - name: Install Dependencies
        if: steps.cache-dependencies.outputs.cache-hit != 'true'
        run: |
          python -m pip install --upgrade pip
          pip install -r requirements.txt
        
      - name: Run Python Script
        run: python main_v1.py

      - name: Commit and Push Logs
        uses: stefanzweifel/git-auto-commit-action@v4
        with:
          commit_message: Automated Change
          repository: .
          commit_user_name: My GitHub Actions Bot # defaults to "github-actions[bot]"
          commit_user_email: my-github-actions-bot@example.org # defaults to "41898282+github-actions[bot]@users.noreply.github.com"
          commit_author: Author <actions@github.com> # defaults to author of the commit that triggered the run

requirements.txt内容：

numpy==1.21.6
oauth2client==4.1.3
pandas==1.5.3
pytz==2022.7.1
Requests==2.31.0
selenium==4.9.0
trycourier==4.4.0

核心问题是缓存步骤未设置id，导致缓存命中状态的判断失效：

• 你的Install Dependencies步骤使用steps.cache-dependencies.outputs.cache-hit判断是否跳过安装，但缓存步骤仅设置了名称Restore Cached Dependencies，并未指定id: cache-dependencies，因此steps.cache-dependencies这个引用不存在，cache-hit的值为空，条件!= 'true'永远成立，所以每次都会执行依赖安装。

另外，缓存~/.cache/pip只是缓存pip下载的包文件，并非已经安装到Python环境的依赖。即使缓存命中，若Python的site-packages目录中没有对应依赖，仍然需要执行安装操作（只是无需重新下载，速度会更快）。

1. 给缓存步骤添加正确的id #

修改缓存步骤，添加id: cache-dependencies，让后续步骤能正确获取缓存命中状态：

- name: Restore Cached Dependencies
  id: cache-dependencies  # 添加这一行
  uses: actions/cache@v3
  with:
    path: ~/.cache/pip
    key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}

2. 优化依赖安装逻辑（可选） #

如果你想完全跳过安装步骤，需要缓存已经安装好的依赖目录（比如虚拟环境），但更简单的方式是保留pip install命令，利用缓存的包文件加速安装——即使执行安装，因为包已经缓存，速度会和跳过安装差不多。可以去掉if条件，让每次都执行安装，pip会自动从~/.cache/pip读取缓存的包，无需从网络下载：

- name: Install Dependencies
  run: |
    python -m pip install --upgrade pip
    pip install -r requirements.txt

修正后的完整Workflow #

name: Daily Python Script

on:
  schedule:
    - cron: "0 19 * * *"
  workflow_dispatch: #Manual trigger
  
jobs:
  build:
    runs-on: ubuntu-latest
    
    permissions:
        contents: write

    steps:
      - name: Set up Python
        uses: actions/setup-python@v4
        with:
          python-version: 3.9

      - name: Update Node.js to v16
        uses: actions/setup-node@v3
        with:
          node-version: 16

      - name: Checkout Code
        uses: actions/checkout@v4

      - name: Restore Cached Dependencies
        id: cache-dependencies
        uses: actions/cache@v3
        with:
          path: ~/.cache/pip
          key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}
                    
      - name: Debug Cache
        run: |
            echo "Cache hit: ${{ steps.cache-dependencies.outputs.cache-hit }}"
            ls -l ~/.cache/pip

      - name: Install Dependencies
        run: |
          python -m pip install --upgrade pip
          pip install -r requirements.txt
        
      - name: Run Python Script
        run: python main_v1.py

      - name: Commit and Push Logs
        uses: stefanzweifel/git-auto-commit-action@v4
        with:
          commit_message: Automated Change
          repository: .
          commit_user_name: My GitHub Actions Bot
          commit_user_email: my-github-actions-bot@example.org
          commit_author: Author <actions@github.com>

内容的提问来源于stack exchange，提问作者tatojunior