ReadMe sample code crashes at run-time

[ploeh]

I'm trying to follow the code examples in the ReadMe file, but it throws an exception at run time:

*Q49343774 Q49343774> tests
*** Exception: <stdout>: hPutChar: invalid argument (invalid character)

FWIW, I tried to simplify the file even further in order to troubleshoot if something else could be the matter:

{-# LANGUAGE TemplateHaskell #-}
module Q49343774 where

import Hedgehog

prop_reverse :: Property
prop_reverse =
  property $ do
    True === True

tests :: IO Bool
tests =
  checkParallel $$(discover)

foo :: () -> String
foo () = "foo"

The reason I included the foo function was that I wanted to verify that there isn't something fundamentally wrong with the file, such as a non-printable character that GHCi would choke on. That doesn't seem to be the case:

*Q49343774 Q49343774> foo ()
"foo"

My environment:

• Operating System: Windows 10 Pro x64, Version 1709, Build 16299.371
• Stack: 1.6.3
• GHC: 8.2.2

Am I doing anything wrong? Is there something I can do to troubleshoot?

[moodmosaic]

See #110 (comment) for a workaround.

[moodmosaic]

I've originally reported this in #32, and the discussion continues in #110 (which shows at least two workarounds).

I haven't investigated further what might be causing this, since I've moved to *nix since then. Perhaps we should close this in favor of #110(?)

[ploeh]

Well, now, at least, it runs, but pretty it isn't:

*Q49343774 Q49343774> :m +System.IO
*Q49343774 Q49343774 System.IO> hSetEncoding stdout utf8
*Q49343774 Q49343774 System.IO> hSetEncoding stderr utf8
*Q49343774 Q49343774 System.IO> tests
ΓöüΓöüΓöü Q49343774 ΓöüΓöüΓöü
  Γ£ô prop_reverse passed 100 tests.
  Γ£ô 1 succeeded.
True

[moodmosaic]

Hmm, perhaps you may also try this workaround as well: #110 (comment), and I think we should close this in favor of #110.

---

FTR, I even tried using the Windows Subsystem for Linux, but there I noticed that stack was really slow, so I ended up using a real *nix virtual machine (Ubuntu and Debian so far).

[ploeh]

Thank you for your help 👍

The workarounds enable me to get code running, but this hardly seems like a satisfactory solution. While I grant that there's small issues with QuickCheck tests on Windows as well (or, at least, on my system), they're nowhere near as conspicuous as these.

ATM, it's not clear to me at all why this problem exists, but if I can do something to help address it, I'd like to offer to spend a few hours doing so, but I'm going to need some guidance.

Whether you want to close this issue in favour of another I have no opinion. Feel free to close this issue if you feel the other one better captures the problem; I can't evaluate whether or not that's the case.

[thumphries]

Yeah, nobody who works on Hedgehog uses Windows right now, so it is hard for us to resolve. We'd love for someone to spend time on it, though. We might be able to add the transliteration hack to the library (it's good enough for GHC) - or follow one of the other avenues in #110.

Closing in favour of #110, where the workarounds are collected.

[moodmosaic]

Well, now, at least, it runs, but pretty it isn't:

*Q49343774 Q49343774> :m +System.IO
*Q49343774 Q49343774 System.IO> hSetEncoding stdout utf8
*Q49343774 Q49343774 System.IO> hSetEncoding stderr utf8
*Q49343774 Q49343774 System.IO> tests
ΓöüΓöüΓöü Q49343774 ΓöüΓöüΓöü
 Γ£ô prop_reverse passed 100 tests.
 Γ£ô 1 succeeded.
True

@ploeh, if you execute chcp 65001 in the console the output should be fine. See #110 (comment).

[ploeh]

Thanks, but

$ chcp 65001
bash: chcp: command not found

[moodmosaic]

Weird... Are you using the Windows Subsystem for Linux or just the Git Bash?

[moodmosaic]

You should enter this in a regular command prompt (cmd.exe) since it's a Windows command, and then start Git Bash from there - - or just use ConEmu which takes care of all this.

[ploeh]

Turns out that it's a .com file, not an .exe. It can be called by writing chcp.com instead of just chcp. It makes the output of the test better, although still not good:

[moodmosaic]

Did you also set stdout/err encoding to UTF-8 as per #110 (comment)?

[ploeh]

I've tried with and without. It makes no difference.

[moodmosaic]

When I have to use Windows, I use the stable version of https://conemu.github.io

In the gif I posted, I'm using the latest stable version of ConEmu.

Perhaps ConEmu deals with UTF-8 far better than cmd.exe

(There are other benefits of using ConEmu anyway.)

[ploeh]

I just tried in cmd instead of Bash. Same problem. I wonder if it's just my system that behaves strangely.

I'll try on another machine...

[moodmosaic]

I wonder if it's the Danish locale (but I'm using the Greek locale so it shouldn't matter).

Still, I'd be curious to see what happens if you try running a Git Bash from inside ConEmu on that machine...

[ploeh]

Perhaps ConEmu deals with UTF-8 far better than cmd.exe

Most likely. Git bash handles this quite poorly, so it's unlikely to get much worse, one could hope. For the last many months, I haven't had the mental bandwidth to look into new tooling, but for the next month or so, I hope that'll change. If so, this is high on my list of things to look at.

I wonder if it's the Danish locale

I wonder the same 😄

[ploeh]

Tried all the above variations on another machine. Same result 😢

Those two machines aren't that different, though. For instance, both run Danish locale. In many ways, I try to keep them in sync with each other...

[moodmosaic]

So when I'm on Windows, I run ConEmu, GHCi, and a code editor, like this:

Notice that I run chcp from inside GHCi via :! chcp 65001, because I spend almost all my time in GHCi, so even things like git, hoogle, etcetera I run them from inside GHCi as well (e.g. :! git status). 😅

[moodmosaic]

Perhaps ConEmu deals with UTF-8 far better than cmd.exe

Most likely.

Indeed, the built-in Windows command prompt (cmd.exe) has issues with UTF-8. ConEmu works fine though:

---

FTR, I've tried this with a rather old, but battle-tested, stable, version of ConEmu, v16.12.06. For a long time, this was the recommended, stable, version on their website.

Perhaps, newer versions of ConEmu (and even Cmder which derives from ConEmu) will work fine as well. You may also try the Windows Subsystem for Linux, but IME it's still not there yet.

[moodmosaic]

@ploeh, even more interesting news.

As an alternative to the built-in Windows command prompt (cmd.exe), ConEmu and Cmder, one can simply use the terminal inside VSCode by setting it to a Git Bash: