GitHub上Docker容器构建失败：找不到PR合并引用

报错详情 #

#0 building with "builder-d99a4367-77ea-4ed0-93ed-c4feadc1693d" instance using docker-container driver

#1 [internal] load git source https://github.com/***/repo.git#refs/pull/9/merge
#1 0.121 Initialized empty Git repository in /var/lib/buildkit/runc-overlayfs/snapshots/snapshots/1/fs/
#1 ERROR: repository does not contain ref refs/pull/9/merge, output: ""
------
 > [internal] load git source https://github.com/***/repo.git#refs/pull/9/merge:
0.121 Initialized empty Git repository in /var/lib/buildkit/runc-overlayfs/snapshots/snapshots/1/fs/
------
ERROR: failed to solve: failed to read dockerfile: failed to load cache key: repository does not contain ref refs/pull/9/merge, output: ""
Error: buildx failed with: ERROR: failed to solve: failed to read dockerfile: failed to load cache key: repository does not contain ref refs/pull/9/merge, output: ""

现有工作流配置 #

# This workflow will install Python dependencies, run tests and lint with a single version of Python
# For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-python

name: Python application

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

permissions:
  contents: read

jobs:
  build:

    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v4
    - name: Set up Python 3.11
      uses: actions/setup-python@v4
      with:
        python-version: "3.11"
    - name: Install dependencies
      run: |
        python -m pip install --upgrade pip
        pip install flake8 pytest
        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
    - name: Lint with flake8
      run: |
        # stop the build if there are Python syntax errors or undefined names
        flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
        # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
        flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
    #- name: Test with pytest
    #  run: |
    #    pytest

docker:
  runs-on: ubuntu-latest
  steps:
    -
      name: Set up QEMU
      uses: docker/setup-qemu-action@v3
      run: echo "::debug::QEMU set up completed"
    -
      name: Set up Docker Buildx
      uses: docker/setup-buildx-action@v3
      run: echo "::debug::Docker Buildx set up completed"
    -
      name: Login to Docker Hub
      uses: docker/login-action@v3
      with:
        username: ${{ secrets.DOCKERHUB_USERNAME }}
        password: ${{ secrets.DOCKERHUB_TOKEN }}
      run: echo "::debug::Logged in to Docker Hub"
    -
      name: Log environment variables
      run: |
        echo "::debug::GITHUB_REF: $GITHUB_REF"
        echo "::debug::GITHUB_SHA: $GITHUB_SHA"
        echo "::debug::GITHUB_REPOSITORY: $GITHUB_REPOSITORY"
    -
      name: Build and push
      uses: docker/build-push-action@v5
      with:
        push: true
        tags: xxxxxxx/yyyyyy:latest
      run: echo "::debug::Started building and pushing Docker image"

问题原因 #

1. Docker构建Job未检出代码：docker job里缺少actions/checkout@v4步骤，Buildx无法获取本地代码上下文，只能尝试从Git仓库拉取指定ref。但PR合并后，GitHub会自动删除refs/pull/9/merge这类临时PR ref，导致拉取失败。
2. 构建上下文未明确指定：默认情况下docker/build-push-action会尝试基于Git上下文构建，在push到main分支的场景下，这个逻辑会错误引用已被删除的PR ref。

修复方案 #

1. 添加代码检出步骤 #

在docker job的所有步骤最开头添加代码检出操作：

- uses: actions/checkout@v4

2. 明确指定构建上下文（推荐） #

修改Build and push步骤，指定使用当前目录作为构建上下文，避免歧义：

- name: Build and push
  uses: docker/build-push-action@v5
  with:
    context: .
    push: true
    tags: xxxxxxx/yyyyyy:latest

3. 可选：限制Docker构建仅在push事件触发 #

如果不需要在PR打开时运行Docker构建，可以给docker job添加执行条件，只在push到main分支时触发：

docker:
  if: github.event_name == 'push'
  runs-on: ubuntu-latest
  steps:
    # ... 原有步骤内容

内容的提问来源于stack exchange，提问作者Andrea