0.18 alpha: elm-make fails to generate correct JS when animation-frame is installed

[eeue56]

The code: https://gist.github.com/eeue56/e2f9d66fb8ae6dbaec5bd1a976d4d4e6

elm-package.json

{
    "version": "1.0.0",
    "summary": "helpful summary of your project, less than 80 characters",
    "repository": "https://github.com/user/project.git",
    "license": "BSD3",
    "source-directories": [
        "."
    ],
    "exposed-modules": [],
    "dependencies": {
        "elm-lang/animation-frame": "1.0.1 <= v < 2.0.0",
        "elm-lang/core": "5.0.0 <= v < 6.0.0",
        "elm-lang/html": "2.0.0 <= v < 3.0.0"
    },
    "elm-version": "0.18.0 <= v < 0.19.0"
}

Main.elm

import Html exposing (..)

main = text "hello"

Problem

Run elm-make Main.elm when animation-frame is in the package file.

Expected output:

A HTML page with hello displayed.

Actual output:

An error on line 1740 of the generated JS:Uncaught TypeError: Cannot read property 'fromArray' of undefined

Possible solution

• Looks like List is not imported before Cmd
• This is somehow caused by including animation-frame in the package.
• The compiled code for Platform.Cmd turns [] into _elm_lang$core$Native_List.fromArray([]));. However, _elm_lang$core$Native_List has not been imported yet.
• Therefore it should be possible to fix it by importing Native.List or List in the first import in Cmd. Or, add Native_List to the import tree whereever list literal syntax is used.

[process-bot]

Thanks for the issue! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[evancz]

I'm not sure if this is the ideal fix, but it works. Here is my assessment:

• The use of fromArray([1,2,3]) came from someone saying that the JS output was not readable. Perhaps that concern has decreased since a few years ago. (In other words, there was no technical motivation for it being this way.)
• It should be quicker in theory because there is nothing to inline. I tested this change with the perf comparison from recently, and it does pretty much the same, which is kind of odd.
• For the sake of keeping the code around native stuff simple, I did not want to design an import syntax in JS comments so that there could be ordering constraints between native modules. So I think we could also resolve this by adding import List to Platform.Cmd and Platform.Sub.

Feel free to say something if this seems like a bad move for some specific reason.

[eeue56]

My only comment is that broken imports for Native seems to come up fairly often (in 0.17 there was the Json.Encode issue), so it might be worth investing some time into a js import system. This move seems fine for now though.

[nphollon]

Importing animation-frame still does not work. The error I am getting (for Noah's same sample program) is

TypeError: _elm_lang$core$Native_Scheduler is undefined

Should we re-open this issue, or should I create a new one?

[evancz]

New one with SSCCE would be best!