Submodules should compile to the same type (objects) as file-level modules

[ELLIOTTCABLE]

Currently, if I create two ML modules in separate files,

$ cat src/test.ml
let hi _ = print_endline "Hello"

$ cat src/test_sub.ml
let sup _ = print_endline "Sup"

$ cat src/blah.js
const Test = require('./test.bs')
const Sub = require('./test_sub.bs')

Test.hi()
Sub.sup()

$ node src/blah.js
Hello
Sup

… but if I inline one of those into another, parent module …

$ cat src/test2.ml
let hi _ = print_endline "Hello"

$ cat src/blah2.js
const Test = require('./test2.bs')
const Sub = Test.Sub

console.log("Test.hi:", typeof Test.hi)
console.log("Sub.sup:", typeof Sub.sup)
console.log("Sub:", typeof Sub)
console.log("Sub (JSON):")
console.log(Sub)

$ node src/blah2.js
Test.hi: function
Sub.sup: undefined
Sub: object
Sub (JSON):
[ [Function: sup] ]

Is that … an array of functions? What!?

---

Coming from ML, where submodules are very often used to break down APIs, in exactly the same way as is done in JavaScript — Jest.Runner.Only over here, require('mocha').reporters.Base over there.

I can fake this by basically manually constructing my entire ‘to be exported’ API in a special file which then becomes the "main" for npm; but I really think it's preferable for BuckleScript to, with minimum effort, publicize exactly the API that one's ML interfaces already expose … no?

I hope this feedback is useful! I found this behaviour very surprising.

[bobzhang]

hi @ELLIOTTCABLE Yes, this is an known prioritized issue. There are some technical challenges to change the current runtime representation of submodules, once we finish upgrading to the new compiler, we will revisit the issue.