onBeforeSetupMiddleware()

in packages/react-scripts/config/webpackDevServer.config.js [112:122]


    onBeforeSetupMiddleware(devServer) {
      // Keep `evalSourceMapMiddleware`
      // middlewares before `redirectServedPath` otherwise will not have any effect
      // This lets us fetch source contents from webpack for the error overlay
      devServer.app.use(evalSourceMapMiddleware(devServer));

      if (fs.existsSync(paths.proxySetup)) {
        // This registers user provided middleware for proxy reasons
        require(paths.proxySetup)(devServer.app);
      }
    },