Ionic/Angular项目启动遇ajv-errors错误：Cannot read property 'allErrors' of undefined

报错信息 #

启动项目时控制台输出：

[ng] NOT SUPPORTED: option jsonPointers. Deprecated jsPropertySyntax can be used instead.
[ng] An unhandled exception occurred: Cannot read property 'allErrors' of undefined
[ng] See "/private/var/folders/3f/chjh7cx96mv1zkr690ytb0yr0000gn/T/ng-RX4zto/angular-errors.log" for further details.

错误日志文件内容：

[error] TypeError: Cannot read property 'allErrors' of undefined
    at module.exports (/Users/skel/web/scratk/gettwoit-frontend/node_modules/ajv-errors/index.js:4:18)
    at Object.<anonymous> (/Users/skel/web/scratk/gettwoit-frontend/node_modules/webpack-dev-server/node_modules/schema-utils/src/validateOptions.js:22:1)
    at Module._compile (node:internal/modules/cjs/loader:1109:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1138:10)
    at Module.load (node:internal/modules/cjs/loader:989:32)
    at Function.Module._load (node:internal/modules/cjs/loader:829:14)
    at Module.require (node:internal/modules/cjs/loader:1013:19)
    at require (node:internal/modules/cjs/helpers:93:18)
    at Object.<anonymous> (/Users/skel/web/scratk/gettwoit-frontend/node_modules/webpack-dev-server/node_modules/schema-utils/src/index.js:7:25)
    at Module._compile (node:internal/modules/cjs/loader:1109:14)

问题原因 #

该错误由ajv-errors与ajv版本不兼容导致：webpack-dev-server依赖的schema-utils使用了旧版ajv-errors，而项目中安装的ajv版本过高（如7.x及以上），两者不兼容引发报错。同时jsonPointers警告也是因为ajv版本差异导致的旧选项弃用提示。

解决步骤 #

1. 锁定ajv版本到兼容的6.x版本（推荐6.12.6）
   • 若使用yarn，直接在package.json中添加：

     "resolutions": {
       "ajv": "6.12.6"
     }
     

   • 若使用npm，先安装版本锁定工具：

     npm install -g npm-force-resolutions
     

     再在package.json中添加：

     "scripts": {
       "preinstall": "npx npm-force-resolutions"
     },
     "resolutions": {
       "ajv": "6.12.6"
     }
     

2. 清理旧依赖文件

   rm -rf node_modules package-lock.json yarn.lock
   

3. 重新安装依赖

   npm install # yarn用户执行 yarn install
   

4. 重新启动项目

   ionic serve # 或 ng serve
   

内容的提问来源于stack exchange，提问作者Skel