TypeError: Cannot read property 'Reflect' of undefined

TypeError: Cannot read property 'Reflect' of undefined
    at eval (/file/4hqwYFw6FKw1njvzEl3VUh/PLUGIN_62_SOURCE:47142)
    at eval (/file/4hqwYFw6FKw1njvzEl3VUh/PLUGIN_62_SOURCE:47158)
    at Object../node_modules/reflect-metadata/Reflect.js (/file/4hqwYFw6FKw1njvzEl3VUh/PLUGIN_62_SOURCE:48248)
    at __webpack_require__ (/file/4hqwYFw6FKw1njvzEl3VUh/PLUGIN_62_SOURCE:20)

tsconfig

{
  "compilerOptions": {
    "target": "es2017",
    "outDir": "dist",
    "jsx": "react",
    "lib": [
      "DOM",
      "ES2015.Reflect"
    ],
    "experimentalDecorators": true,
    "removeComments": true,
    "allowSyntheticDefaultImports": true,
    "noImplicitAny": false,
    "moduleResolution": "node",
    "typeRoots": [
      "./node_modules/@types",
      "./node_modules/@figma"
    ]
  }
}

weback

const HtmlWebpackInlineSourcePlugin = require('html-webpack-inline-source-plugin')
const HtmlWebpackPlugin = require('html-webpack-plugin')
const path = require('path')

module.exports = (env, argv) => ({
    mode: argv.mode === 'production' ? 'production' : 'development',

    // This is necessary because Figma's 'eval' works differently than normal eval
    devtool: argv.mode === 'production' ? false : 'inline-source-map',

    entry: {
        ui: './src/ui.tsx', // The entry point for your UI code
        code: './src/code.ts', // The entry point for your plugin code
    },

    target: 'node',

    module: {
        rules: [
            // Converts TypeScript code to JavaScript
            { test: /\.tsx?$/, use: 'ts-loader', exclude: /node_modules/ },

            // Enables including CSS by doing "import './file.css'" in your TypeScript code
            { test: /\.css$/, loader: [{ loader: 'style-loader' }, { loader: 'css-loader' }] },

            // Allows you to use "<%= require('./file.svg') %>" in your HTML code to get a data URI
            { test: /\.(png|jpg|gif|webp|svg|zip)$/, loader: [{ loader: 'url-loader' }] },
        ],
    },

    // Webpack tries these extensions for you if you omit the extension like "import './file'"
    resolve: { extensions: ['.tsx', '.ts', '.jsx', '.js'] },

    output: {
        filename: '[name].js',
        path: path.resolve(__dirname, 'dist'), // Compile into a folder called "dist"
    },

    // Tells Webpack to generate "ui.html" and to inline "ui.ts" into it
    plugins: [
        new HtmlWebpackPlugin({
            template: './src/ui.html',
            filename: 'ui.html',
            inlineSource: '.(js)$',
            chunks: ['ui'],
        }),
        new HtmlWebpackInlineSourcePlugin(),
    ],
})

Start with the reported stack trace in node_modules/reflect-metadata/Reflect.js and compare it with tsconfig and the webpack configuration. Reproduce the failure using the ui.tsx and code.ts entry points, then verify that the generated plugin output no longer throws this TypeError.