Blank Page and Error 500 when using elm-reactor

[peacememories]

Hello, and thanks for all your work on the elm platform :)

I have an issue that has apparently surfaced before and was fixed, in #59

I was advised to create a new issue instead of just commenting on the old one, so I've duplicated my comment here :)

On MacOS, with the latest elm-platform (0.18 if I am not mistaken), and a very simple Dice.elm:

module Dice exposing (..)

import Html exposing (Html, div, text)

main =
    div [] [ text "Hello World!" ]

About 90% of the time when I refresh the page localhost:8000/Dice.elm I am greeted with a blank page, and the console outputs the following:

[Error] Failed to load resource: the server responded with a status of 500 (Internal Server Error) (Dice.elm, line 0)
[Error] ReferenceError: Can't find variable: runElmProgram
    Global Code (Dice.elm:10)

The resource in question is /_compile/Dice.elm which returns an error code 500.

Apparently when I add an error to my code, the proper error description page always gets shown, so the problem seems to occur after the page has been built?

I have uninstalled and reinstalled elm-platform a few times, and originally I was using the elm binaries from Homebrew, with the same result.

There could be a problem with my setup, but if so I can't find it.

[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.

[peacememories]

Something I hadn't done was test with other browsers, and, to my surprise it seems to only happen with Safari? Which is kind of weird because the developer tools indicate an error code in the response.

[danpalmer]

I'm experiencing the same issue, also in Safari. Anything I can do to help debug this let me know!

Interestingly, the 500s only seem to happen when there isn't a compile error. I can reliably refresh an error page and always receive 200 (as far as I can tell).

[rl-king]

I'm also experiencing this issue, also only safari (11.0), re-installed Elm and still the same. It's weirdly inconsistent I've had moments it did work on 15 refreshes, restarted Safari, and got the error again.

[zwilias]

So it appears that Safari, for reasons that are beyond me, will sometimes request everything twice in rapid succession on separate TCP streams, yet it only listens to the results of the second request. The first request actually succeeds!

The second request suffers from a race condition where the first /_compile/.. request removes "it-is-safe-to-delete-this-file.js" before the second request can read it.

The actual 500 response reads like so:

A web handler threw an exception. Details:\n it-is-safe-to-delete-this-file.js: openBinaryFile: does not exist (No such file or directory)

[peacememories]

Oh, wow. I mean I guess a race condition should be fixed anyway, but... why, Safari?^^'

[mlooney]

+1 for this, driving me nuts, Version 11.0.1 (13604.3.5) still has this issue :(

[bryce13950]

Same thing here

[trs123]

Same here with Safari Technology Preview (Release 60 (Safari 12.0, WebKit 13606.1.23.1)). Chrome Version 67.0.3396.99 (Offizieller Build) (64-Bit) works fine. OS: macOS High Sierra 10.13.5

[sloane-shark]

Also affecting me, I would really appreciate something to address this. Safari: 11.1.2 macOS: 10.13.6

[josephsweeney]

Affecting me as well. macOS: 10.13.6 Safari: 11.1.2

Getting a 500 consistently though, makes elm-reactor unusable.