Maybe check for case mismatch between modules and files?

[nateabele]

Quick Summary: Case mismatches between modules and file paths work fine on OSX but break on *nix

SSCCE

import Foo.Bar

-- Then make a module file at `foo/Bar.elm` (note directory case)
-- Works fine on Mac, breaks on Linux

• Elm: 0.19.0
• Browser: N/A
• Operating System: OSX / HFS+ (Case-Insensitive)

Additional Details

I've been working on an Elm project on a Mac, then recently went to set it up on CI in a Linux environment and ran into this. Clearly this isn't Elm's fault, or Elm's problem, strictly speaking—however, even after having run into this dozens of times in my career, it took a couple hours before checking this even occurred to me.

On that basis, I thought that having the compiler look for and warn about something like this would be in keeping with the spirit of Elm. Just a thought! Thanks. 😃

[evancz]

I would like to do this, but it is quite difficult to reliably get the capitalization on certain platforms.

The only way it can be done with Haskell is with canonicalizePath as far as I know. The problem is that function also gets rid of symlinks. Imagine a file named src/Foo/Bar.elm that is actually a symlink to some other file with some other name. Using canonicalizePath would say "hey, this name is not correct!" But the name is correct!

So doing a better job requires making some choices about allowing/disallowing symlinks in certain scenarios that I was not comfortable doing in 0.19.1.

I would be very happy to give errors in all cases (and I tried!) but it is blocked on figuring out some scheme that can work across OSes and works alright with symlinks.

[nateabele]

The only way that I've been able to do something like this in the past is to walk up the hierarchy, get a directory listing for each path segment, and compare. Very hacky and makes some assumptions.

Probably not worth the effort for a fringe case like this, but I suppose you could throw a note in the 'bad import' error about making sure the case matches?