Regression in preset-react 7.9.x.

Bug Report

• I would like to work on a fix!

Current Behavior

After upgrade @babel/preset-react from 7.8.x to 7.9.x all tests in my project are failing with message:

Error: ProgressBar(...): Nothing was returned from render. This usually means a return statement is missing. Or, to render nothing, return null.

After bisecting babel I have found a commit which breaks my project. https://github.com/babel/babel/commit/748897be0772d3569c92c26e061ba05ac26563b4

Those lines https://github.com/babel/babel/pull/11154/files#diff-8c3c9c6362e23bd456da3fb129f49a57L10-R12 gave me a clue how to workaround it. So, I added {pragma: "React.createElement"} and it helped.

Babel Configuration (babel.config.js, .babelrc, package.json#babel, cli command, .eslintrc)

• Filename: babel.config.js Original

module.exports = function(api) {
  const isTest = api.env('test');

  const envOptions = isTest
    ? {
      "targets": {
        "node": "current"
      }
    }
    : {
      modules: false,
      useBuiltIns: 'usage',
      corejs: 3,
      // debug: true,
    };

  return {
    "presets": [
      ["@babel/preset-env", envOptions],
      "@babel/preset-react"
    ],
    "plugins": [
      "@babel/plugin-proposal-class-properties"
    ],
  };
};

• Filename: babel.config.js With workaround

module.exports = function(api) {
  const isTest = api.env('test');

  const envOptions = isTest
    ? {
      "targets": {
        "node": "current"
      }
    }
    : {
      modules: false,
      useBuiltIns: 'usage',
      corejs: 3,
      // debug: true,
    };

  return {
    "presets": [
      ["@babel/preset-env", envOptions],
      ["@babel/preset-react", {
        pragma: "React.createElement",
      }],
    ],
    "plugins": [
      "@babel/plugin-proposal-class-properties"
    ],
  };
};

Environment

  System:
    OS: Linux 5.4 Debian GNU/Linux bullseye/sid
  Binaries:
    Node: 12.16.1 - ~/apps/nodejs/bin/node
    Yarn: 1.22.4 - /usr/bin/yarn
    npm: 6.13.4 - ~/apps/nodejs/bin/npm
  npmPackages:
    @babel/core: ^7.1.0 => 7.9.0 
    @babel/plugin-proposal-class-properties: ^7.0.0 => 7.8.3 
    @babel/preset-env: ^7.0.0 => 7.9.0 
    @babel/preset-react: ^7.0.0 => 7.9.1 
    babel-core: ^7.0.0-bridge.0 => 7.0.0-bridge.0 
    babel-eslint: ^10.0.0 => 10.1.0 
    babel-jest: ^25.1 => 25.1.0 
    babel-loader: ^8.0.0 => 8.1.0 
    eslint: ^6 => 6.8.0 
    jest: ^25.1 => 25.1.0 
    webpack: ^4.0.0 => 4.42.0 

[bopfer]

@nicolo-ribaudo Disregard, sorry! Seems like CI was pulling in the old version for some reason. I updated all my packages, rebuilt my yarn.lock file, and everything is working now.

[nicolo-ribaudo]

Yes sorry, this was a bug in @babel/generaror.

https://www.npmjs.com/package/@babel/generator