注: webpack 版本为 4+

使用 create-react-app 创建的项目默认不支持 less语法, 所以要手动配置

暴露配置文件

create-react-app 生成的项目看不到 webpack 相关的配置文件，需要先暴露出来，使用如下命令即可

npm run eject

安装依赖

yarn add less less-loader antd babel-plugin-import 

修改配置

1. package.json

  "babel": {
    "presets": [
      "react-app"
    ],
    "plugins": [
      [
        "import",
        {
          "libraryName": "antd",
          "style": true
        }
      ]
    ]
  }

2. webpack.config.js

/* start */ 和 /* end */ 之间为添加的代码

• 定义全局变量

// style files regexes
const cssRegex = /\.css$/;
const cssModuleRegex = /\.module\.css$/;
const sassRegex = /\.(scss|sass)$/;
const sassModuleRegex = /\.module\.(scss|sass)$/;
/* start */
const lessRegex = /\.less$/;
const lessModuleRegex = /\.module\.less$/;
/* end */

• 定义全局样式

    if (preProcessor) {
      loaders.push(
        {
          loader: require.resolve('resolve-url-loader'),
          options: {
            sourceMap: isEnvProduction && shouldUseSourceMap
          }
        },
        {
          loader: require.resolve(preProcessor),
          options: {
            sourceMap: true
          }
        }
      );
      /* start */
      let loader = require.resolve(preProcessor);
      if (preProcessor === 'less-loader') {
        loader = {
          loader,
          options: {
            modifyVars: {
              // 主题
              'primary-color': ' #1890ff '
            },
            javascriptEnabled: true
          }
        };
      }
      loaders.push(loader);
      /* end */
    }

• 配置 less-loader

找到 oneOf 数组, 在里面添加

            // Opt-in support for SASS (using .scss or .sass extensions).
            // By default we support SASS Modules with the
            // extensions .module.scss or .module.sass
            {
              test: sassRegex,
              exclude: sassModuleRegex,
              use: getStyleLoaders(
                {
                  importLoaders: 2,
                  sourceMap: isEnvProduction && shouldUseSourceMap
                },
                'sass-loader'
              ),
              // Don't consider CSS imports dead code even if the
              // containing package claims to have no side effects.
              // Remove this when webpack adds a warning or an error for this.
              // See https://github.com/webpack/webpack/issues/6571
              sideEffects: true
            },
            // Adds support for CSS Modules, but using SASS
            // using the extension .module.scss or .module.sass
            {
              test: sassModuleRegex,
              use: getStyleLoaders(
                {
                  importLoaders: 2,
                  sourceMap: isEnvProduction && shouldUseSourceMap,
                  modules: {
                    getLocalIdent: getCSSModuleLocalIdent
                  }
                },
                'sass-loader'
              )
            },
            /* start */
            {
              test: lessRegex,
              exclude: lessModuleRegex,
              use: getStyleLoaders({ importLoaders: 2 }, 'less-loader')
            },
            {
              test: lessModuleRegex,
              use: getStyleLoaders(
                {
                  importLoaders: 2,
                  modules: {
                    getLocalIdent: getCSSModuleLocalIdent
                  }
                },
                'less-loader'
              )
            },
            /* end */

重启项目

警告是不是消失了 : )