New validation in Babel 7.7.0 breaks Metro

[leonid-shevtsov]

Babel 7.7.0 will throw an error for an empty Identifier node: babel/babel#10621

This breaks a specific place in Metro:
https://github.com/facebook/metro/blob/master/packages/metro/src/ModuleGraph/worker/JsFileWrapping.js#L81

function functionFromProgram(
  program: Object,
  parameters: $ReadOnlyArray<string>,
): Object {
  return t.functionExpression(
    t.identifier(''),
    parameters.map(makeIdentifier),
    t.blockStatement(program.body, program.directives),
  );
}

Replacing the empty string with anything but empty resolves the issue.

I don't have enough familiarity with Metro to suggest a proper identifier. :)

Babel: 7.7.0
Metro: 0.57
Yarn: 1.19.1

Metro config:

module.exports = {
  resolver: { sourceExts: ['js', 'jsx'] },
};

Babel config:

{
  "presets": ["module:metro-react-native-babel-preset"],
  "plugins": [
    [
      "transform-inline-environment-variables",
      {
        "include": ["SENTRY_DSN"]
      }
    ]
  ]
}

[loganfsmyth]

Instead of t.identifier(''), Metro should be passing null as the identifier. Looks like this has been working by chance until now because Babel didn't have validation and no other plugins happened to trip over the empty identifier.

[nicolo-ribaudo]

We plan to re-introduce this validation in Babel 8 (babel/babel#10746).

[MichaReiser]

Closing as this has been fixed in ed8a04f