.babelrc

{
  "env": {
    "development": {
      "presets": [
        "next/babel",
        "@zeit/next-typescript/babel"
      ],
      "plugins": [
        [
          "styled-components",
          {
            "ssr": true,
            "displayName": true
          }
        ],
        [
          "@babel/plugin-proposal-decorators",
          {
            "legacy": true
          }
        ]
      ]
    },
    "production": {
      "presets": [
        "next/babel",
        "@zeit/next-typescript/babel"
      ],
      "plugins": [
        [
          "styled-components",
          {
            "ssr": true,
            "displayName": true
          }
        ],
        [
          "@babel/plugin-proposal-decorators",
          {
            "legacy": true
          }
        ]
      ]
    },
    "test": {
      "presets": [
        "@babel/preset-typescript",
        ["next/babel", {"preset-env": { "modules": "commonjs" }}]
      ],
      "plugins": [
        ["styled-components", { "ssr": true, "displayName": true }],
        ["@babel/plugin-proposal-decorators", { "legacy": true }],
        ["babel-plugin-sass-vars"]
      ]
    }
  }
}