I am trying to setup my Haskero (Visual Studio Code extension that uses Intero) for my Haskell project, yet I get the following error :
app\Main.hs:3:1: error:
Failed to load interface for `Lib'
Use -v to see a list of the files searched for.
Steps to reproduce:
stack new project
cd project
stack build intero
stack exec intero
> :l app/Main.hs
app/Main.hs :
module Main where
import Lib
main :: IO ()
main = someFunc
src/Lib.hs :
module Lib
( someFunc
) where
someFunc :: IO ()
someFunc = putStrLn "someFunc"
I had similar issue occuring in Visual Studio Code.
Under the hood Haskero properly uses:
stack ghci --with-ghc intero --no-build --no-load
However Haskero assumes that the stack project is the working directory loaded to VSCode. If instead the stack project is one of the subdirectories then the same error appears in IDE, because stack command is run from that main directory. At least it's what happens currently with Haskero 1.3.1.
The solution is to always make sure that stack project is equal to working directory in VSCode.
I don't have experience with Haskero but can duplicate the problem with a plain old Intero installation on a Linux machine.
The issue is that you're invoking the Intero backend via stack exec instead of stack ghci. You would observe the same problem if you tried using stack exec ghci instead of stack ghci to invoke a usual GHC interactive session (see the documentation for stack ghci for more information).
Instead of stack exec intero, try:
stack ghci --with-ghc intero --no-build --no-load
and it should work okay.
(Note that stack exec intero actually works okay if you stack build your project first, but the interactive session is still supposed to be invoked via stack ghci.)
Related
|-aseCswk2
|-app
|-Main.hs
|-src
|-Libs.hs
|-test
|-Spec.hs
|-aseCswk2.cabal
|-Setup.hs
|-package.yaml
...
So i have a Haskell project that uses a Stack build system and is laid out as the example above. If i use $ stack test then my functions in my Libs.hs file are tested with the cases in my Spec.hs file. If i use $ stack build then my file builds successfully and i can use the functions inside $ stack ghci.
However, i want to create an executable of the my Main.hs file but don't know how this is possible. I have tried compiling it using $ ghc Main.hs inside the app directory but get an error saying 'Failed to load interface for Lib' even though i have included it as an import. I have also tried $stack build aseCswk2:exe:aseCswk2-exe but no .o files are created to run.
Haskell-stack builds the executable in the hidden .stack-work directory. You can find out where the binaries are located that stack uses with:
$ stack path --local-install-root
/haskell/app/.stack-work/install/x86_64-linux/3fa5b3c3fbcd473981eef72c68d572129654cbb7c23af146b50d90e29c41b62f/8.6.5
In this directory, there is, if you build the application, a bin/ directory where the binary is located that has been built.
You can also run the application with:
$ stack run
A minimal reproduction can be found here:
https://github.com/IvanMalison/stack-gtk2hs-bug
Everything works as expected when I use normal stack commands, but when I run the failing command:
stack ghc -- --make main.hs
I get the following error:
main.hs:3:1: error:
Ambiguous interface for ‘Graphics.UI.Gtk’:
it was found in multiple packages: gtk-0.14.6 gtk3-0.14.6
main.hs:4:1: error:
Ambiguous interface for ‘Graphics.UI.Gtk.Abstract.Widget’:
it was found in multiple packages: gtk-0.14.6 gtk3-0.14.6
main.hs:5:1: error:
Ambiguous interface for ‘Graphics.UI.Gtk.Layout.Table’:
it was found in multiple packages: gtk-0.14.6 gtk3-0.14.6
The output of stack exec ghc-pkg -- --no-user-package-db list is https://gist.github.com/f19f900988f49e4d03cd61f1cab48baa . This output makes me expect that the reason that this is happening is that some other stack install required gtk (not gtk3 which is what is specified as a dependency in this package) and somehow this package is visible from the stack ghc command for some reason.
Am I misunderstanding the stack ghc command? Shouldn't this essentially do the same thing as stack build?
There's no builtin way to do this with stack currently. However, it is possible to get stack ghci to do this. The most straightforward way to do it is to make a cabal package which has the executable target. However, if you really want to just use straight ghc, there is a way. Copy-pasting from my comment here:
stack ghc works a bit differently than stack ghci. It's essentially a synonym for stack exec -- ghc, which will run the right compiler with the right databases, but won't set up anything related to your local packages like include directories etc. Note that stack ghci takes TARGET arguments whereas stack ghc does not. Retrospectively, this is a bit inconsistent, but stack ghc came before stack ghci.
It does make sense to have the ability to do something like this, though not sure how to best achieve that. Some potential options:
--no-interactive argument on stack ghci. Would be a bit obtuse. Weird to run a ghci command when, though it would be using the stack ghci logic.
Add --target TARGET option to stack ghc, to tell it to use the environment of a particular local package target.
Here's a workaround for now. Put the following in ~/.local/bin/stack-run-ghc.sh and make it user executable:
#/bin/sh
ghc $(echo "$*" | sed 's/--interactive//g')
This takes the arguments, removes --interactive, and calls ghc. With this, I can build stack using ghc via the following:
stack ghci --with-ghc stack-run-ghc.sh --ghci-options src/main/Main.hs
I created a very simple project with stack. It contains: an executable, a library and test targets in the associated cabal file. When I load the code to ghci via stack ghci, I can't access test there, even if they are in separate module. Is there any way to use it in such a way?
Try stack ghci (your project name):(the test suite name). Then you should be able to enter main and your tests will run.
Example:
If your .cabal project file had the following values:
name: ExampleProject
...
test-suite Example-test
Then the command to run would be stack ghci ExampleProject:Example-test
(edit suggested by #Chris Stryczynski)
To watch the test and src directories so they are updated when you reload with :r, run:
stack ghci --ghci-options -isrc --ghci-options -itest ExampleProduct:Example-test
I have just two files A.hs and B.hs in a directory dir (so no cabal or stack.yaml files). A imports B (with just import B). Running stack ghci and loading A then fails, complaining about the import. Is there a way to get this working? Running the system-wide ghci, everything works fine of course.
The reason I'm asking is that I've switched to intero for Emacs, which uses stack, and I'd like to be able to use intero for random small bits of code that I have lying around.
Versions: ghc 8.0.1, stack 1.1.2.
I have
mainLogger.hs
Logger.hs
in my local directory where the mainLogger.hs reference the Logger module.
When in stack ghci I :load mainLogger.hs I get the following error message :
mainLogger.hs:6:18:
Could not find module ‘Logger’
It is not a module in the current program, or in any known package.
However if I can compile stack exec -- ghc mainLogger.hs and run stack runghc mainLogger2.hs or have stack exec -- ghci load the module correctly.
Anyone knows what is preventing stack ghci from locating module in the local directory ?
ps : I am not using any cabal file or stack.yaml file in this directory, so it falls back onto my global stack.yaml config
You should be able to load both if you do it at the same time:
:load Logger.hs mainLogger.hs
I don't know if you can get GHCi to look for the missing module in the current folder if you have no cabal file but if you create/initialize one this is not necessary.
This issue should now be fixed in the latest version of stack. It seems that when a module imported a local module, stack wasn't including the local directory in its module search path. In the latest 1.5.1. version of stack, this has been fixed - so you should be able to just type
stack ghci mainLogger.hs