title: React-MobX Error: The 'decorators' plugin requires a 'decoratorsBeforeExport' option, whose value must be a boolean
body: <p>I get the following error: If you are migrating from Babylon/Babel 6 or want to use the old decorators proposal, you should use the 'decorators-legacy' plugin instead of 'decorators'.</p>
  
  <p><strong>package.json</strong></p>
  
  <pre><code>"@babel/plugin-proposal-decorators": {
        "version": "7.1.2",
        "resolved": "https://registry.npmjs.org/@babel/plugin-proposal-decorators/-/plugin-proposal-decorators-7.1.2.tgz",
        "integrity": "sha512-YooynBO6PmBgHvAd0fl5e5Tq/a0pEC6RqF62ouafme8FzdIVH41Mz/u1dn8fFVm4jzEJ+g/MsOxouwybJPuP8Q==",
        "requires": {
          "@babel/helper-plugin-utils": "^7.0.0",
          "@babel/helper-replace-supers": "^7.1.0",
          "@babel/helper-split-export-declaration": "^7.0.0",
          "@babel/plugin-syntax-decorators": "^7.1.0"
        }
      },
  
   "@babel/plugin-syntax-decorators": {
        "version": "7.1.0",
        "resolved": "https://registry.npmjs.org/@babel/plugin-syntax-decorators/-/plugin-syntax-decorators-7.1.0.tgz",
        "integrity": "sha512-uQvRSbgQ0nQg3jsmIixXXDCgSpkBolJ9X7NYThMKCcjvE8dN2uWJUzTUNNAeuKOjARTd+wUQV0ztXpgunZYKzQ==",
        "requires": {
          "@babel/helper-plugin-utils": "^7.0.0"
        }
      },
  
  "babel-plugin-syntax-decorators": {
        "version": "6.13.0",
        "resolved": "http://registry.npmjs.org/babel-plugin-syntax-decorators/-/babel-plugin-syntax-decorators-6.13.0.tgz",
        "integrity": "sha1-MSVjtNvePMgGzuPkFszurd0RrAs=",
        "dev": true
      },
      "babel-plugin-transform-decorators-legacy": {
        "version": "1.3.5",
        "resolved": "https://registry.npmjs.org/babel-plugin-transform-decorators-legacy/-/babel-plugin-transform-decorators-legacy-1.3.5.tgz",
        "integrity": "sha512-jYHwjzRXRelYQ1uGm353zNzf3QmtdCfvJbuYTZ4gKveK7M9H1fs3a5AKdY1JUDl0z97E30ukORW1dzhWvsabtA==",
        "dev": true,
        "requires": {
          "babel-plugin-syntax-decorators": "^6.1.18",
          "babel-runtime": "^6.2.0",
          "babel-template": "^6.3.0"
        }
      },
  "requires": {
       "@babel/plugin-proposal-decorators": "7.1.2",
  }
  </code></pre>
  
  <p><strong>tsconfig.json</strong></p>
  
  <pre><code>{
      "compilerOptions": {
          "experimentalDecorators": true,
          "allowJs": true
      }
  }
  </code></pre>