Effect.fn should preserve value of function's length property

[bwbuchanan]

What is the problem this feature would solve?

Currently, functions returned by Effect.fn have a length of 0. This means that consumers cannot accurately determine the number of arguments to the function.

This problem manifests with cucumber, which verifies that functions passed as step definitions have the expected number of arguments.

What is the feature you are proposing to solve the problem?

Effect.fn should use Object.defineProperty to set the length of the returned function to the value of body.length.

What alternatives have you considered?

I have an ugly workaround in the form of a wrapper function for Effect.fn.

const fn: typeof Effect.fn = function (nameOrBody: any, ...pipeables: any[]) {
  const argsCount = typeof nameOrBody === 'function' ? nameOrBody.length : pipeables[0].length;

  const newFn = Effect.fn(nameOrBody, ...pipeables);

  Object.defineProperty(newFn, 'length', { value: argsCount });

  return newFn;
} as any;

Configuring the length property of a Function is widely supported.