Babel 7 + Inversify 4 + WebPack 4 - Unexpected character '@' on @inject

Question

I have a typescript Vue SPA project where I use Inversify .

I used awesome-typescript-loader for compiling my typescript source code; now I want to switch to Babel but when I compile my application webpack raise this error:

Module parse failed: Unexpected character '@' (38:25) You may need an
appropriate loader to handle this file type.
| _inherits(ReportService, _BaseService);
| > function ReportService(@inject(TYPES.Urls)
| urls) {
| var _this;
@ ./app/Ioc/container.ts 6:0-54 14:39-52
@ ./app/startup.ts

.babelrc

{
    "presets": [
        "@babel/env",
        "@babel/preset-typescript"
    ],
    "plugins": [
        ["@babel/plugin-proposal-decorators", { "legacy": true }],
        "@babel/proposal-class-properties",
        "@babel/proposal-object-rest-spread"
    ]
}

tsconfig.json

{
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "test/*": [ "test/*" ],
      "@/*": [ "app/*" ]
    },
    "lib": [ "es6", "dom" ], // es6 minimum required for Promise
    "target": "es6", // Required for vuetify
    "strict": true,
    "module": "esNext",
    "moduleResolution": "node",
    "experimentalDecorators": true, // Required for @Component for Vue
    "strictPropertyInitialization": false,
    "noImplicitAny": false,
    "allowUnusedLabels": false,
    "noEmit": true,
    "noUnusedLocals": true,
    "noImplicitReturns": true,
    "emitDecoratorMetadata": true
  },
  "exclude": [
    "node_modules"
  ]
}

webpack.config.js

const config = {
    entry: {
        app: './app/startup.ts'
    },
    output: {
        path: path.resolve(__dirname, "wwwroot", "dist"),
        filename: '[name].js'
    },
    module: {
        rules: [
            {
                test: /\.(html)$/,
                use: {
                    loader: 'html-loader'
                }
            },
            {
                test: /\.ts$/,
                exclude: /node_modules/,
                use: {
                    loader: 'babel-loader'
                }
            },
            {
                enforce: "pre",
                test: /\.js$/,
                loader: "source-map-loader",
                exclude: [
                    path.join(process.cwd(), 'node_modules')
                ]
            },

        ]
    },
    resolve: {
        alias: {
            'vue': 'vue/dist/vue.esm.js',
            '@': path.join(__dirname, 'app')
        },
        extensions: ['.vue', '.ts', '.js']
    },
    optimization: {
        splitChunks: {
            cacheGroups: {
                vendors: {
                    test: /[\\/]node_modules[\\/]/,
                    name: "vendors",
                    chunks: "all",
                    enforce: true,
                    priority: -10
                }
            }
        }
    }
}

If I use awesome-typescript-loader chained to babel-loader

{
    test: /\.ts$/,
    exclude: /node_modules/,
    use: ['babel-loader', 'awesome-typescript-loader']
}

and remove the unnecessary babel plugin and presets it work.

Answer 1

That's is a really annoying issue of @babel/preset-typescript implementation:
it strips types and doesn't emit the relative Metadata in the output code.

The only thing that helped is babel-plugin-transform-typescript-metadata

{
  "plugins": [
    "babel-plugin-transform-typescript-metadata",
    ["@babel/plugin-proposal-decorators", { "legacy": true }],
    ["@babel/plugin-proposal-class-properties", { "loose": true }],
  ],
  "presets": [
    "@babel/preset-typescript"
  ]
}