According to the wiki entry,
It packages up the files needed to build the project
I have a simple executables-only .cabal project, which basically contains
Executable myprog
hs-source-dirs: src
main-is: MyMain.hs
and is made up of some additional .hs files below src/ beyond src/MyMain.hs. E.g., src/Utils.hs and a few others.
cabal build has no problems building myprog, and compiles the required additional .hs files below src/, but cabal sdist does not, thus creating a dysfunctional source-tarball. What am I doing wrong? How do I tell cabal to include all source files below hs-source-dirs?
As a side-note, with GNU Autotools, there was a make distcheck target, which would first build a source-tarball, and then try to build the project via the newly generated source-tarball, thus ensuring everything's ok. Is there something similar for cabal, in order to make sure my source-tarball is sound?
You should list the other Haskell files in the .cabal file, inside the Executable stanza.
other-modules: Utils AFewOthers
The distribution only includes source files that are listed in your .cabal file. Cabal has no other way to detect which source files are in your package. You could still build because cabal build calls ghc --make, and ghc will find and compile all the source files it needs.
Related
I have a Haskell library that I am developing using Stack. As I am developing the library, I like to write small test/experimentation programs that use the library. I keep a collection of these test programs for myself in a directory locally. These test modules are very quick and informal, and not appropriate to include as unit tests in the committed library code. Typically, most of them aren't even maintained and won't compile against the latest version of the library, but I keep them around in case I want to update them later. When I'm working on a test program, I want it to build against my working copy of the library, with any changes that I've made to the library locally.
How should I set up my Stack build environment for this situation? Here are some options I've tried, and the problems with each options.
Two Cabal packages, one Stack configuration. The stack.yaml file lists both packages and defines the build environment for both at once.
Problem: The stack.yaml file needs to be included as part of the committed library source code, so that other developers can build the library from source reproducibly. I don't want the public stack.yaml file for my library to include build information for my local test projects.
Problem: As far as I know, to make this work I need to have a .cabal file that lists all the executables and modules for my test programs. This is annoying to update whenever I want to throw together a quick experimental script, and will fail to build any of the test programs if I have even a single module that doesn't compile. I can't have a .cabal file with no sections, because Cabal gives "No executables, libraries,tests, or benchmarks found. Nothing to do.", and because this offers nowhere to list build-depends.
Create a Cabal sandbox for the test programs. Use cabal sandbox add-source to add the local library as a package. See also this answer.
Problem: Using Cabal sandboxes instead of Stack reintroduces a lot of the dependency problems that Stack is supposed to fix, such as using the system-global GHC instead of the GHC defined by the resolver.
Have a separate stack.yaml for the test programs. Add the library under packages as location: 'C:\Path\To\Local\Library' and set extra-dep: true for that dependency. (See here for more info on this feature.) Don't put any other Cabal packages under packages in the stack.yaml for the test programs. Use stack runghc to invoke test programs within the scope of their stack.yaml.
Problem: I just can't get this one to work. Running stack build inside the test program directory gives "Error parsing targets: The project contains no local packages (packages not marked with 'extra-dep')". Running stack runghc acts as if no dependencies are present at all. I don't want to add a Cabal package for the test programs because this has the same problem as option 1 with needing to construct an explicit .cabal file describing the modules to build.
Problem: Stack build configuration info that I want to be identical between the library and the test programs has to be copied manually. For example, if I change the resolver in my library's stack.yaml, I also need to change it in the stack.yaml for my test programs separately.
Have a directory inside my working copy of the library that contains all of my test programs. Use stack runghc to invoke test programs in the context of the library.
Problem: I'd like the directory with my test programs to be outside of the directory containing my library source code and build configuration, so that I don't have to tell the version control for my library to ignore my test code, and can have my own local version control just for the test programs.
Problem: Only works with a single local library dependency. If my test programs need to depend on local working copies of two different libraries with their own stack.yaml files, I'm out of luck.
Add a symbolic link inside my working copy of the library to a separate directory that contains all of my test programs. Navigate through the symlink and use stack runghc to invoke test programs in the context of the library.
Problem: Super awkward to use, especially since I'm on Windows and Windows has terrible symlink support.
Problem: Still need to tell my version control system to ignore the symlink.
Problem: Still only works with a single library dependency.
If only one local library is involved, I use option 4. You can put your tests outside the directory of your library, and either invoke stack from the directory of your library, or using --stack-yaml path/to/library/stack.yaml.
Otherwise, I use option 3, creating a separate stack project without setting extra-dep.
...
packages:
- 'path/to/package1'
- 'path/to/package2'
...
I can't think of a good workaround for the issue of configuration duplication. There would otherwise be conflicts if multiple packages specified different resolvers/package versions.
Edit: Actually a stub library works better, so edited to add.
I think the way to get #3 to work is -- under your scratch program directory -- (1) add . under packages in stack.yaml alongside the location/extra-dep: true package:
packages:
- '.'
- location: ../mylib
extra-dep: true
(2) create an executable clause in scratch.cabal that points to a stub main program (i.e., a "Hello World" program that compiles but need not do anything) which depends on your library:
executable main
hs-source-dirs: src
main-is: Stub.hs
build-depends: base
, mylib
default-language: Haskell2010
or a library clause with no exposed modules, again that depends on your mylib library:
library
hs-source-dirs: src
build-depends: base >= 4.7 && < 5
, mylib
default-language: Haskell2010
and (3) run stack build in the scratch directory. This should build and register mylib, and now stack runghc Prog1.hs should work fine for running programs that depend on mylib modules.
If you use the executable approach, the stub program is compiled as a side effect but otherwise ignored. If you use the library approach, it looks like the stub library isn't even built; and you then have the option of actually building a scratch library by adding some exposed modules of shared code for your test programs to use, if it's convenient, so the stub library might be best.
None of this solves the problem of keeping stack.yaml info like the resolver version in sync, but it seems to address all the problems you list in 1, 2, 4, and 5. In particular, it should work fine for test programs that depend on multiple local libraries you're developing.
This bugs me time and again, basically if I create a test-suite in the cabal configuration I add the projects src folder to the test suites hs-source-dirs section and repeat all dependencies in build-depends. A typical project might look like:
-- in file "foo.cabal"
library
build-depends: a, b, c
exposed-modules: Foo, Bar
hs-source-dirs: src
test-suite tests
build-depends: foo, a, b, c
hs-source-dirs: test
The other option is to include src in the test suites hs-source-dirs as well.
Both of them require me to specify all build dependencies in the test case, as far as I know. Is there a way around this?
It should work as is but there is a reported bug when you use it with cabal repl
Overall it seems work with cabal test but if you try to load the test-file into cabal repl you might get an error like this:
Could not find module ‘XYZ’
It is a member of the hidden package ‘XZY-[ver]’.
Perhaps you need to add ‘XYZ’ to the build-depends in your .cabal file.
Use -v to see a list of the files searched for.
So right now it might be a good idea to indeed copy the dependencies but hopefully this will get resolved shortly
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).
Is it possbile to write a Cabal configuration file, which contains multiple Library sections?
I found in the documentation the description of Library section and Executables sections, so it seems, that it is impossible to put more Library section in one Cabal configuration file.
But what should I do if I'm developing several Haskell libraries and several executables
simultaneously and want to compile and test them all?
AFAIK, you can't put more than one library in a cabal file. The name specified in the Name field (at the top level of the cabal file) is used as the name of the library, so there doesn't seem to be a mechanism for specifying names of additional libraries.
In practice, I haven't found this to be a problem. I develop each library in a separate directory, with its own cabal file. Once you run cabal install on a library you've developed, then it can be referenced in the cabal file for your executable (in the Build-Depends section), just the same as a package on Hackage.
So, for example, if you have two libraries with cabal files that look like this:
Name: my-library-1
. . .
and
Name: my-library-2
. . .
Then the cabal file for your executable can reference them like this:
Name: my-program
. . .
Executable run-program
Main-Is: Main.hs
Build-Depends: my-library1,
my-library2,
. . .
You can even require specific versions of your libraries. For example:
Build-Depends: my-library1==1.2.*,
my-library2>=1.3
This is possible in Cabal 2 with internal libraries, so called "convenience" libraries: https://github.com/haskell/cabal/pull/3022. This will not let you install these libraries though, they are just allowed to be composed into the final executables and public library exposed by a .cabal file. If you want to build multiple things in progress, you should use a cabal.project file - http://blog.ezyang.com/2016/05/announcing-cabal-new-build-nix-style-local-builds/ has some information on this.
I found out, that my problem can be easly solved with the newest cabal-dev.
If you've got 2 projects: A and B and you want to develop them in parallel, its nice to use cabal-dev install A B - it will build and install them both to the local cabal-dev repository. If you re-run this command, they will be rebuilt and reinstalled if necessary.
According to the documentation - If you want to register new or override existing package on local cabal-dev hackage, you should use cabal-dev add-source, which basically copy the source and allows you to install it like it was available on hackage.
I have simple program written with haskell, i build it with cabal. For example i my program has next directory structure:
my-prog
* Main.hs
* my-prog.cabal
* SomeDirWithHsFiles
- File1.hs
- File2.hs
I want that when i'll make cabal build and cabal install (maybe something else), SomeDirWithHsFiles with *.hs files, installed like a normal haskell library, and then i'll use File1.hs and File2.hs modules in other programm.
How can i do this?
Thank you.
You need to declare your additional files in a library section, like so:
library
exposed-modules: File1
File2
executable foo
main-is: Main.hs
See for example, xmonad's .cabal file.