I were trying to add cabal-install and Cabal-install to .cabal file but.
At least the following dependencies are missing: Cabal-install -any
Why there is no cabal-install?
So how can I get Distribution.Client.IndexUtils except of embedding cabal-install sources?
and Distribution.Client.IndexUtils too.
Or maybe I can replace it with something?
Unfortunately, cabal-install is a package that provides an executable, but no library. Therefore, there is no easy way to use functionality provided by cabal-install in other tools. A common approach is to write wrapper programs that invoke the cabal binary and query it for information.
Having some of the functionality of cabal-install available as a library is a valid and reasonable goal, but it might take a while before this happens.
As to the error message: If a package installs only an executable, it is not registered as a library with GHC. Therefore, if you list cabal-install as a dependency of another package, you will get the error message that cabal-install is missing (as a library).
Related
I'm trying install tidal in command line this way:
cabal install tidal
but it ends with this message:
Warning: You asked to install executables, but there are no executables in
target: tidal. Perhaps you want to use --lib to install libraries instead.
Return of:
cabal install tidal --lib
is:
Resolving dependencies...
Up to date
If I check ghk-pkg list, there is no package tidal
...
Have somebody similar problem or what I'm doing wrong?
My environment is:
Windows 10 Education
Haskell 8.4.3
Cabal 3.2.0.0
Ghc 8.10.1
Thank you for help.
Like Stack for a longer time, Cabal-install does now (as of 3.2) not really install libraries anymore – in the sense of, change the computer's state so that GHC can access the library on it†. Both tools only install executables now. It used to do that for libraries too, but that was stopped with the now default Nix-style builds.
Now (and, really, also already before), the way to use a library is instead to just depend on it, and let Cabal figure out behind the scenes if it needs to be installed. I.e., you add a .cabal file to your .hs source file with build-depends: tidal in it. Then when you say cabal install ., it will first download and install the library before then using it for building your own executable.
†Of course both Stack and Cabal do technically speaking install libraries, just they don't globally register them. I.e., cabal knows where it has installed the library, but you're not really supposed to know about that. It's in the spirit of continuous integration: if your code builds now with the particular state of libraries you happen to have installed, that's not very reliable. If it builds with just those libraries that are explicitly listed in a project file, the chances are much better that future-you (or somebody else) will still be able to use your code on another computer without hours of figuring out what libraries to install first.
cabal install --lib tidal doesn't install the library binaries in a location managed by ghc-pkg. The binaries remain in the Cabal "store".
What it does is to create a plaintext GHC package environment file that is picked up by standalone invocations of ghc and ghci and tells them where to look for the extra libraries.
By default (as mentioned in the docs) this package environment file will be created at ~/.ghc/$ARCH-$OS-$GHCVER/environments/default and will be picked by ghc and ghci invocations made anywhere.
We can also supply an extra --package-env parameter to create the environment file in a local folder, which will only affect ghc and ghci invocations made in that folder. For example:
cabal install --lib --package-env . tidal
cabal projects themselves ignore environment files, as their package environments are constructed from the build-depends section of the cabal file for the sake of reproducibility. But environment files are useful for not having to create a cabal project in the first place, if you only need it for playing with the library in ghci, or if you are compiling simple programs using ghc only.
When I do cabal --version I see:
cabal-install version 0.14.0
using version 1.14.0 of the Cabal library
so what's the difference? i thought that when i do cabal build i use only one program. why is it split into two separate programs with different versions?
The Cabal library defines how package descriptions are parsed and structured, and describe part of the process of building and installing a package. The cabal-install package defines the cabal application. It uses the library to effectively understand what a package description is.
This is a common structure for software: implement all your pure and reusable business logic in a library (the Cabal library does most, but not all, of the work purely related to package descriptions), and implement all your user interface stuff and other 'details' in an application that uses the library (the cabal-install package defines the CLI tool, and implements the details of fetching packages from Hackage).
I am trying to install Haskell Platform 2014.2.0.0 from source on Red Hat Enterprise Linux 6.5. I have a functional install of Haskell Platform 2012.4.0.0 and GHC 7.4.2 from two years ago, plus a recently-installed Haskell Platform 2013.2.0.0 and GHC 7.6.3 from JustHub.
I've built GHC 7.8.3 from source, but it keeps coming up with seven failures in the test suite. I have no idea if these test failures are innocuous or not. (The test failures are not relevant to my question, but they may become significant later.)
I unpack the source tarball of 2014.2.0.0, read the README. It says that the way to build this iteration of Haskell is with a shell script, which is invoked:
./platform.sh $PATH_TO_GHC_BINDIST_TARBALL
I don't have a GHC binary distribution tarball. So far as I am able to tell, there is no binary distribution tarball of GHC 7.8.3 for any version of Red Hat Enterprise Linux. I have a built GHC 7.8.3. How do I tell platform.sh -- or whatever is underneath it -- that there is no tarball, and it should just use what's in $PATH? Alternately, how do I pack up my existing install of GHC 7.8.3 so that platform.sh will accept it?
The built GHC does not have a 'cabal' command, so the cabal commands in platform.sh are falling back to $PATH, which I can configure to be either of the other installed versions (2013.2/7.6.3 or 2012.4/7.4.2). It doesn't seem to make a difference: neither one recognizes 'cabal --sandbox'. Both result in complaints that I should run 'cd hptool ; cabal install --only-dependencies', which I've done, repeatedly. platform.sh never gets past that point.
If I run the commands in platform.sh by hand, I get to 'cd hptool; cabal build', which errors out: "cabal-1.16.0.2: Run the 'configure' command first.". But there is no 'configure' command available in the hptool directory.
I'm now stuck. How do I build Haskell Platform 2014 on RHEL 6?
You need to use your GHC sources to make your own "bindist." Directions at https://ghc.haskell.org/trac/ghc/wiki/MakingReleases
I managed to get Haskell Platform installed, and functional. I ended up abandoning platform.sh and just hand-installed all the packages in the Haskell Platform tarball -- and their dependencies -- with manual cabal commands. Along with the broken platform.sh, I ran into many problems on the way.
The ones that I remember:
platform.sh will never succeed if you have the stock Haskell Platform 2013 or previous installed. It wants a cabal that recognizes the '--sandbox' option, and cabal 1.18 doesn't know that option. You must have a newer cabal installed than Haskell Platform 2013 provides. (GHC 7.4 or 7.6 appears to be fine, though.)
I had an existing .cabal and .ghc directory, which had incompatible builds and/or versions of various packages. I deleted both directories numerous times while testing things.
cabal install --global behaves rather differently from the default cabal install --user. .cabal contained something useful after I did 'cabal install cabal-install'. It took two or three tries at that to figure out where the new cabal binary went.
ghc and cabal pick up new libraries in .ghc and .cabal, but not new binaries.
Neither GHC nor cabal install default to --enable-shared, except when something wants it. I had to go rebuild everything before that -- all the way back to GHC 7.8.3 itself -- with --enable-shared once that happened.
haddock is ridiculously tightly bound to the version of GHC it was built with. I had to rebuild it to get --enable-documentation to work for anything built with GHC 7.8.3.
The test packages and the text package are so tightly integrated that they have circular dependencies if you try to do 'cabal install text --enable-tests'. Even after installing the most recent version of text and the test packages, cabal still wouldn't run the text test suite, so I gave up and installed text without testing it.
My default environment includes 'LC_ALL=C'. This trips a known bug in cabal -- apparently in all versions -- that breaks some package builds. To work around it, I had to shift it to 'LC_ALL=en_US.utf8'. I have no idea if the packages affected will work if you have LC_ALL, or any of the other locale variables such as LANG or LC_<anything else>, set to C.
cabal install --global is terribly inconsistent about where packages get stored. We split out individual packages into their own subdirectories, and then build a symlink tree in a known place out of all those subdirectories. So ghc is in its own subdirectory of /usr/sup/ghc-7.8.3; Haskell Platform is in another subdirectory, /usr/sup/haskell-platform-2014.2.0.0. I consistently used --prefix=/usr/sup/haskell-platform-2014.2.0.0 on every 'cabal install' command, but even then, some libraries ended up in /usr/sup/ghc-7.8.3.
Both GHC and Haskell Platform have a dictionary of what's built and where it is -- perhaps as a workaround for the install location inconsistency -- in /usr/sup/ghc-7.8.3/lib/ghc-7.8.3/package.conf.d/package.cache. If that package dictionary isn't world-readable, ghc breaks. What it should do is look at the actual file structure to find things. Given that ghc breaks if the dictionary isn't available, the file shouldn't be called 'cache', as a cache miss shouldn't cause catastrophic failure. Perhaps rename it to 'package-mandatory-dictionary'?
Ultimately, it all installed, but I have to wonder about the damage I did from so much banging my head on the wall.
I'd like to, within a client program, use the GHC API from a
modified version of GHC. Its easy enough to get the GHC sources
and build and install the modified GHC, but installing the
modified GHC causes all older (Cabal) dependencies to break.
Consequently, I cannot use the GHC API as ghc -v says:
package ghc-7.0.3-... is unusable due to missing or recursive dependencies:...
Any clues on how to proceed?
Thanks!,
Ranjit.
You must build a custom version of GHC first, then install all the packages you need. That way, everything will be linked against your custom GHC, and you will be fine.
As I know cabal is a program to manage installation of packages like FreeBSD's pkg_add.
But there is another tool called ghc-pkg. I don't know why there are two different programs. What's the role of each of them and how are they related?
Cabal is a building and packaging library for Haskell, kind of "Haskell autotools". It reads .cabal files and Haskell packages usually have a file Setup.hs which uses Cabal to build the package. Then there's also cabal command provided by the cabal-install package. It provides commands for running Setup.hs script and some package management functions, like installing packages directly from Hackage. You should read this blogpost by Ivan Miljenovic which explains the role of Cabal, cabal-install and Hackage quite well.
ghc-pkg is a lower-level tool for poking GHC's package database. Cabal is intended to work with every Haskell compiler, whereas ghc-pkg is obviously specific to GHC. You can't use ghc-pkg to build anything, you can just register packages you've built otherwise.
cabal is just an interface layer to ghc-pkg with some added features. It's only important to know ghc-pkg because uninstall functionality was not added to cabal, but can be done directly with ghc-pkg.