Is it possible to tell Cabal to expose all modules while building a library?
Right now I have to provide very long list of modules in the exposed-modules cabal configurtion file section.
The modern answer is stack + hpack instead of using explicit cabal config. It could automatically expose package modules and provides many other enhancements.
You have to list all modules in the cabal configuration file. In your case, you just put the list of modules after exposed-modules:. There is no simpler way to write a list of modules.
Cabal cannot automatically find the files that are part of an executable or library, so it relies on the list of modules in the configuration file. Unlike GHC, cabal cannot find modules based on import statements in the source code. If you don't list every module, then you may be able to build the project (because GHC can find source files), but other commands such as cabal sdist will not access the source files that aren't listed.
Related
Do I need to manually edit the *.cabal file's build-depends section to add package as a project dependency?
Or perhaps there is a more convenient way that is not as error prone as manually mangling with build files is.
Thinking about functionality that pretty much any package manager I used has, namely
apt install
npm i
nuget install
Install Package
and so on. Does such functionality exist in Cabal?
There is no better way at the moment. The answer #danidiaz gave is essentially correct -- cabal-edit will automatically update cabal files for you. The plan is to import similar functionality into cabal directly. This was remains blocked on an exactprinter that can parse and emit cabal files precisely -- and work on that exactprinter is now underway.
I've installed the Gloss graphics library with cabal. I also installed the gloss examples package.
Now I want to test the examples. This may seem like a silly question, but how do I actually use the package gloss-examples? I understand I can now import the gloss library to a haskell module but how do I test the gloss-examples I installed i.e. how do I use the gloss-example package?
Building gloss-examples produces a handful of executables, as specified by the Executable entries in the .cabal file. (Another telltale sign of executable-only packages is the lack of entries for modules at the front page of the Hackage docs.) In Linux, the default destination of such executables is ~/.cabal/bin. According to the answers to this question, in OS X the default is ~/Library/Haskell/bin/cabal, unless you are using the Homebrew package manager, which changes it to ~/.cabal/bin. In Windows, it is %APPDATA%\cabal\bin. See also: the Installation paths section in Cabal's user guide.
The gloss-examples package does not install any modules and you do not work with it as a library. Instead, it builds executables (see here) under the names gloss-*. Just run those executables which are wherever you have cabal installing the binaries (typically $HOME/.cabal/bin).
I have a stack multi-package project where the "multi-package" is zip-conduit-0.2.2.2 (I needed to tweak some dependency versions to get it to compile with nightly-2015-10-12).
I use zip-conduit in the main package and I also want to in Setup.hs in order to be able to package up zip files.
I have build-type: Custom in my cabal file and stack build attempts to build Setup.hs. The problem is that building Setup.hs cannot find the dependency zip-conduit-0.2.2.2.
Can I use a multi-package dependency in Setup.hs? If so how? and if not, what is my alternative?
Note: I have seen this reference https://github.com/commercialhaskell/stack/pull/899, but I don't understand it.
It looks like you need to set the explicit-setup-deps setting to true for that package. It's unfortunate that Stack can't handle this situation automatically, but without dependency information in .cabal files, there seems to be no alternative.
See the linked issues from the documentation if you're interested in the history here.
I don't think it is possible to declare package dependencies for Setup.hs itself.
Some ideas:
Require that the dependent packages have already been installed.
Have Setup.hs shell out to an external command to perform the zipping, and just require that the external command has to exist.
Make the installer program an additional exe target in the cabal file. Before proceeding with the build of the library, Setup.hs can build the installer program target, then build the library, then use the built installer exe to install the library.
How can I find out what needs to go into the module.cabal build-depends? I mean, some modules may already be part of the Haskell platform whilst others may not? How to I find out/know what I must write here so that the module I offer will install with cabal on the majority of Haskell installations "out there"?
My situation is that I have it working on my systems, but cannot remember for what import I actually had to install an other module and what was part of the Haskell Platform that I use. How do I now best find the way from my situation to a cabal installable package?
If you use Cabal to build your project, it will only look at the modules listed in the .cabal file, even if you have other modules installed locally.
So all you have to do is run it as is (with nothing in the depends declaration) and it will give you an error for each module you need to specify. I think the error even tells you the name of the package.
I know a Haskell module name, but I can't figure out in what package it is defined. This is bad because I can't compile without a package exposing this module.
Specificaly it is Text.Regex that I can't locate, but I would like to know how to solve that problem in general.
http://www.haskell.org/ghc/docs/latest/html/users_guide/packages.html
ghc-pkg find-module Text.Regex
But that only works for (a) recent GHCs, and (b) packages installed on your system.
You can also grep through the package file (e.g. /usr/lib/ghc-6.8.2/package.conf) to see what's installed.
You can also use either the haskell API search engines hoogle or the hackage search engine hayoo.
Text.Regex is in the package regex-base, and a few others built on top of it.
If you're using Cabal and you have the package installed, you can just try to compile it with cabal build, and Cabal will inform you of which package you forgot to add to your dependencies:
Main.hs:1:8:
Could not find module `Text.Regex':
It is a member of the hidden package `regex-compat-0.93.1'.
Perhaps you need to add `regex-compat' to the build-depends in your .cabal file.
Use -v to see a list of the files searched for.
The best tools are:
hoogle; or
hayoo.
Both are search engines for Haskell modules and functions.
If you are using Debian and the Debian-provided packages, there is a global documentation index at /usr/share/doc/ghc-doc/html/libraries/index.html which lists the package in the last column.