使用Yarn Berry与GitHub Action构建CI时遇YAML语法异常排查

在使用Yarn Berry搭配GitHub Action搭建CI工作流时，触发了如下YAMLException错误：

Error: YAMLException: end of the stream or a document separator is expected at line 3, column 11:
    nodeLinker: pnp
              ^
    at generateError (/usr/local/lib/node_modules/yarn/lib/cli.js:126542:10)
    at throwError (/usr/local/lib/node_modules/yarn/lib/cli.js:126548:9)
    at readDocument (/usr/local/lib/node_modules/yarn/lib/cli.js:127914:5)
    at loadDocuments (/usr/local/lib/node_modules/yarn/lib/cli.js:127950:5)
    at load (/usr/local/lib/node_modules/yarn/lib/cli.js:127971:19)
    at safeLoad (/usr/local/lib/node_modules/yarn/lib/cli.js:127993:10)
    at parse (/usr/local/lib/node_modules/yarn/lib/cli.js:64242:18)
    at module.exports.exports.default (/usr/local/lib/node_modules/yarn/lib/cli.js:63793:96)
    at loadRcFile (/usr/local/lib/node_modules/yarn/lib/cli.js:57527:58)
    at /usr/local/lib/node_modules/yarn/lib/cli.js:57501:14

用户提供的.yarnrc.yml文件内容如下：

.yarnrc.yml

nodeLinker: pnp

yarnPath: .yarn/releases/yarn-4.4.1.cjs

同时附上GitHub Action工作流配置：

name: CI Workflow

on:
  push:
    branches: [main, develop]
  pull_request:
    branches: [main, develop]

jobs:
  build:
    runs-on: ubuntu-latest

    strategy:
      matrix:
        node-version: [18.x, 20.x]

    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Set up Node.js ${{ matrix.node-version }}
        uses: actions/setup-node@v4
        with:
          node-version: ${{ matrix.node-version }}
          cache: 'yarn'

      - name: Enable Corepack
        run: corepack enable

      - name: Install dependencies
        run: yarn install

      - name: Run tests
        run: yarn test --passWithNoTests

      - name: Build project
        run: yarn build

错误原因 #

问题出在.yarnrc.yml文件的第一行——你错误地将文件名.yarnrc.yml写入了文件内容中。YAML解析器会把这行当作配置内容的一部分，但它既不是合法的键值对，也不符合YAML的语法结构，直接导致了解析失败。

修复方案 #

1. 修正.yarnrc.yml文件：删除第一行的.yarnrc.yml文字，保留正确的配置项：

nodeLinker: pnp

yarnPath: .yarn/releases/yarn-4.4.1.cjs

2. 优化GitHub Action工作流：为了避免系统全局Yarn版本与项目配置版本冲突，在Enable Corepack步骤后添加指定项目Yarn版本的步骤：

- name: Use project configured Yarn version
  run: yarn set version .yarn/releases/yarn-4.4.1.cjs

内容的提问来源于stack exchange，提问作者gmulb