I try to generate documentation for my executable using cabal haddock. My project structure looks like this:
~/.../project_name
project_name.cabal
Setup.hs
src/
Main.hs
Data/
...
test/
MainTestSuite
...
When I run cabal haddock --executable it fails with the following error message:
module ‘projects-0.1.0.0:Main’ is defined in multiple files: dist/build/tmp-8215/src/Main.hs
dist/build/tmp-8215/./Setup.hs
The Source.hs file has these contents:
import Distribution.Simple
main = defaultMain
The ghc Version is 7.8.3 and the haddock version is 2.14.3.
Related
I am currently self studying Haskell. I am just a beginner so I haven't yet had a need to use cabal or stack. But right now I need to test some of my code using QuickCheck.
From this link that I found https://github.com/haskell/cabal/blob/master/doc/cabal-commands.rst , I ran the command cabal install --lib QuickCheck --package-env . and got the following output :
axiom#pop-os:~/Desktop/Haskell-Learning/Course/Homework 10$ cabal install --lib QuickCheck --package-env .
Resolving dependencies...
Up to date
In the same directory, I have a .hs file and in that when I tried to import Test.QuickCheck the linter gives an error as the package doesnt seem to be available for importing.
Then I ran cabal repl --build-depends QuickCheck and then in ghci I was able to import it. But still it was not importing in the code file.
Then when I just opened ghci by firing the command ghci , the following shows up, which suggests that there is a package environment here in this directory :
GHCi, version 8.10.7: [https://www.haskell.org/ghc/](https://www.haskell.org/ghc/) :? for help
Loaded package environment from /home/axiom/Desktop/Haskell-Learning/Course/Homework 10/.ghc.environment.x86\_64-linux-8.10.7
Prelude> import Test.QuickCheck
Prelude Test.QuickCheck> :q
Even after above, that is, being able to import QuickCheck in GHCi, the import is still not working in the file.
After this, I tried the following :
axiom#pop-os:~/Desktop/Haskell-Learning/Course/Homework 10$ cabal install QuickCheck
Resolving dependencies...
Up to date
Warning:
############################################################
# WARNING: Installation might not be completed as desired! #
############################################################
The command "cabal install [TARGETS]" doesn't expose libraries.
* You might have wanted to add them as dependencies to your package. In this
case add "QuickCheck" to the build-depends field(s) of your package's .cabal
file.
* You might have wanted to add them to a GHC environment. In this case use
"cabal install --lib QuickCheck". The "--lib" flag is provisional: see
https://github.com/haskell/cabal/issues/6481 for more information.
axiom#pop-os:~/Desktop/Haskell-Learning/Course/Homework 10$ cabal install --lib QuickCheck
Resolving dependencies...
Up to date
The import still doesn't work.
Any help is appreciated !
The method I ended up finding is the following :
Run the following in the directory where you have your haskell file where you want to import an external package :
cabal init
This will general a small number of files and such in that directory.
Add the name of the package that you want to use in the .cabal file that was generated . For example, I wanted to use QuickCheck so my .cabal file looks like this :
cabal-version: 2.4
name: Homework10
version: 0.1.0.0
author: Name Surname
maintainer: name#email.com
extra-source-files: CHANGELOG.md
executable Homework10
main-is: Main.hs
build-depends: base ^>=4.14.3.0, QuickCheck
hs-source-dirs: app
default-language: Haskell2010
Then in the same directory, run the following :
cabal build
Then when you try to import the package in your .hs, you should be able to do so.
I have a test project with the following structure:
Test
Test
Test.hs
Test.cabal
Test.hs is an empty module:
{-|
Description: Test
Test
-}
module Test.Test () where
Test.cabal:
cabal-version: 3.0
name: Test
version: 0.0.0
library
build-depends: base
exposed-modules: Test.Test
When I run cabal haddock it puts the docs in dist-newstyle/build/x86_64-windows/ghc-8.10.1/Test-0.0.0/doc.
Is there any way to redirect the output of cabal haddock to some other directory instead of burying it five layers deep in dist-newstyle?
My project structure is as follows:
~/.../project_name
project_name.cabal
Setup.hs
src/
Main.hs
Data/
...
test/
MainTestSuite
...
I have (amongst others) the following lines in my project.cabal:
build-type: Simple
...
executable project_name
main-is: Main.hs
...
hs-source-dirs: src
When I cabal configure (works fine) and then cabal build I get the error message:
cabal: can't find source for Setup in src, dist/build/autogen
It works when I put Source.hs in src but this seems messy to me and I haven't seen this in other projects, where Source.hs is always in the project root. How do I get cabal to find Source.hs?
As an aside: What's the purpose of Source.hs anyways?
The problem was caused by accidently adding the Source file as a dependency in other-modules in the cabal-file of the project ... that caused all the trouble.
hs-source-dirs: ., src comes to mind as a fast fix.
That's what my projects use, and I generate my cabal files automatically (so I suppose that's the default).
I have a cabal file with a custom build to (calls Setup.hs to perform some preprocessing). But Setup.hs imports Project.Preprocessor, which is under src as show below.
project.cabal
Setup.hs
src/Project/Preprocessor.hs
src/Project/OtherFiles...
This fails since src is not included (as in runghc -isrc Setup.hs build).
dist\setup\setup.hs:3:18:
Could not find module Project.Preprocessor
...
Is there any way to include an extra source directory for build process?
I.e. like runghci -isrc Setup.hs (but from cabal build).
EDIT: I did verify that runghc -isrc Setup.hs build executes. :-)
Thanks!
I have a src directory. In this directory I have Main.hs file and Test directory. In the Test directory I have Test.hs module. I need to compile it with cabal.
In my cabal file I have:
Executable main
-- .hs or .lhs file containing the Main module.
Main-is: src/Main.hs
and
-- Modules not exported by this package.
Other-modules: Test.Test
When I do cabal configure it's OK, but when I try to cabal build I get the following error:
cabal build
Preprocessing executables for main-0.0.1...
cabal: can't find source for Test/Test in ., dist/build/autogen
How can I correctly build Main.hs and some other directories with .hs files?
Thank you.
If Test.Test is defined in src/Test/Test.hs, you need
hs-source-dirs: src
in the Executable section of your Cabal file. Note that your main-is file path should be relative to the source directory, so in this case, you should change it to Main.hs.