Flow libdef only works with ESM, not CommonJS

[Yeiniel Suárez Sosa]

Description

Currently Flow libdef definition shipped with ava 1.0.0-beta.3 do not support using ava as a Commonjs module. I realize that ava recommend using babel but the project source code do not use babel. I know that when running ava babel is implicitly used but i don't think using different EcmaScript flavours is correct.

Test Source

/** Test case for the package entry point */

// @flow

"use strict";

const test = require("ava");
const mlTrainerApi = require(".");

test("expose the Application symbol", t => {
  t.truthy(mlTrainerApi.Application);
});

Error Message & Stack Trace

Error ┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈ src/index.test.js:10:1

Cannot call test because a callable signature is missing in module ava [1].

 [1]  7│ const test = require("ava");
      8│ const mlTrainerApi = require(".");
      9│
     10│ test("expose the Application symbol", t => {
     11│   t.truthy(mlTrainerApi.Application);
     12│ });
     13│



Found 1 error

Config

None

Command-Line Arguments

Copy your npm build scripts or the ava command used:

npx flow check

Environment

Node.js v8.10.0
linux 4.15.0-12-generic
ava version 1.0.0-beta.3
npm version 5.6.0

[Mark Wubben]

If I recall correctly, Flow doesn't let you define a module that can be used both as ESM and CommonJS. I did manage to get this to work in TypeScript.

Perhaps there is a way to import the TestInterface and cast the const test to that? I have to admit that I don't know much about Flow — writing the current definition was already quite tricky. If somebody else has a solution please let us know! 😄