metro-named-module-factories.js

// ModuleGraph/worker/JSFileWrapping.js

function normalizeFileName(name) {
  return '_' + name.replace(/[^a-zA-Z0-9]/g, '_')
}

function wrapModule(
  // ...
  , fileName) {
  // ...
  const factory = functionFromProgram(fileAst.program, params, normalizeFileName(fileName))
  // ...
}

function functionFromProgram(program, parameters, name) {
  return t.functionExpression(
    t.identifier(name || ''),
    parameters.map(makeIdentifier),
    t.blockStatement(program.body, program.directives),
  )
}

// JSTransformer/worker.js

var _JsFileWrapping$wrapM = JsFileWrapping.wrapModule(
          // ...
          filename
        );

facebook/metro#585