I want to use reactive-banana in my new Haskell project. I never used cabal-install or stack before. I created a directory and initialized project files in it using stack new. I see now 2 files in the directory: new-template.cabal and stack.yaml.
How do I set dependencies and make sure they are downloaded and compiled?
At first I tried to add - reactive-banana-0.8.0.2 in stack.yaml under extra-deps:, but both stack build and stack solver didn't download it. Then I augmented a part called library in new-template.cabal to this:
library
hs-source-dirs: src
exposed-modules: Lib
build-depends: base >= 4.7 && < 5
, reactive-banana >= 0.8
default-language: Haskell2010
Every time I tried to run stack build, it crashed with an error and suggestion to add some package to stack.yaml under extra-deps:, and this happened three times until finally all packages installed, and I could import them in stack ghci REPL.
So my question is, what is the idiomatic way to use stack? Which of these 2 files should I use to specify dependencies and other project metadata? What is the sample workflow of an average Haskell developer with stack?
When using stack I generally don't put any versions bounds in my .cabal file. I let the resolver and extra-deps setting in the stack.yaml file determine which versions of packages to select.
Here is a stack.yaml file which brings in reactive-banana-0.8.1.2:
flags: {}
packages:
- '.'
extra-deps:
- reactive-banana-0.8.1.2
- psqueues-0.2.0.2
resolver: lts-2.17
In my .cabal file I just have:
build-depends: base >= 4.7 && < 5, reactive-banana
The reactive-banana version is pinned by the stack.yaml file.
If you want to use GHC 7.10 change the resolver to something like nightly-2015-06-17.
I determine the extra-deps iteratively, by just running stack build and adding whatever dependencies are missing to the stack.yaml file until all dependencies are satisfied.
You will only need to do this with packages which are not in Stackage - like reactive-banana. A great many of commonly used packages are in Stackage and their versions will be determined by the resolver setting.
In the default configuration, stack works with two package databases: a centralised per-user one and a project-specific one. The centralised database only pulls packages from Stackage, a subset of Hackage with known-to-be-compatible packages, while you can put whatever you want on the project-specific database. All packages you use must be in the cabal file, but those not on Stackage (that is, the ones that will go to the project-specific database) must also be listed in the extra-deps section of stack.yaml. reactive-banana is not on Stackage, so you need to add it to stack.yaml, like this:
# etc.
extra-deps:
- reactive-banana-0.8.1.2
# etc.
stack solver can fill in the extra dependencies in stack.yaml for you.
Related
I have a Haskell library I wrote that I compile with stack.
I now need to use it in another Haskell stack project.
In order to do that, I have added its current version to the extra_deps of my new project's stack.yaml and listed it among the build_depends of one its executables.
When I run stack build, however, it obviously tries to download the library from the internet. How do I specify that the library is local and where to find it?
Thanks in advance!
You can use github coordinates in the extra-deps section of your stack.yaml.
extra-deps:
- github: snoyberg/http-client
commit: a5f4f30f01366738f913968163d856366d7e0342
Then add the dependency in your package.yaml:
dependencies:
- http-client >= 0.1.0.0
I am trying to add dependency of gtk2hs-buildtool to my Haskell project but following error while building stack.
In the dependencies for TicTacToe-0.1.0.0:
gtk2hs-buildtools needed, but the stack configuration has no specified version (latest matching
version is 0.13.5.4)
needed since TicTacToe is a build target.
TicTacToe.cabal file:
library
exposed-modules:
TicTacToeEngine
other-modules:
Paths_TicTacToe
hs-source-dirs:
src
build-depends:
base >=4.7 && <5,
gtk2hs-buildtools
default-language: Haskell2010
If you are using stack tool you shouldn't touch the <packagename>.cabal file. stack is in charge to generate it from package.yaml. Despite of the fact that is a common practise to modify the <packagename>.cabal, development workflow will be easier if you don't.
The files you are interested in (and the ones that stack tool uses) are the stack.yaml and package.yaml.
In stack.yaml you should see an entry called resolver: lts-XX.XX. That means that your dependencies version are managed such that they match those in the given lts (a.k.a. snapshot). You can go to https://www.stackage.org/, click on your lts version and search for the gtk2hs-buildtools package to get the right version for your project (example: lts-12.26 uses gtk2hs-buildtools-0.13.4.0). In your package.yaml, in the dependencies section write the entry entry - gtk2hs-buildtools
From lts-13.11 and above gtk2hs-buildtools is not available in stackage, so you need to add it as an extra-dep. in the stack.yaml, in the section extra-dep add the following entry gtk2hs-buildtools-0.13.4.0 (or the version number you'd like to use). Then add in the package.yaml and entry gtk2hs-buildtools. It is necessary to add the entry in both files. Refer to stack docs o understand why.
Just to ensure you can build your project, your files should something look like the following:
if using resolver above or equal to 13.11
stack.yaml
resolver: lts-13.11
extra-deps:
- gtk2hs-buildtools-0.13.4.0
package.yaml
dependencies:
- base
- gtk2hs-buildtools
if using resolver below 13.11
stack.yaml
resolver: lts-12.26
extra-deps:
package.yaml
dependencies:
- base
- gtk2hs-buildtools
I'm trying to upgrade the dependencies of the pipes-files package, so that it can be included in the latest stack LTS. The pipes-files package does not contain a stack.yaml file, and the pipes-files.cabal file contains quite some upper and lower bounds on its dependencies, e.g.:
base >=4.7 && <4.10
, transformers >=0.3 && <0.6
, transformers-base >=0.3 && <0.6
-- and quite some more ...
Is there a tool that I can run to get the latest versions of each of these dependencies? The closest thing I could find was packdeps but it will require me to search for the dependencies one by one.
Preliminary notes:
hierarchy, a dependency of pipes-files, has the same issue you are trying to work around -- it is not in Stackage and has version bounds outdated with respect to the latest LTS. That means you'll first have to get it to build successfully, and then add your tweaked version of it to the extra-deps in the stack.yaml of pipes-files.
cabal gen-bounds, which "suggest[s] dependency version bounds that conform to Package Versioning Policy", is, in principle, the right tool for the job. However, getting cabal-install to behave according to the restrictions of a Stack-centric environment is not always straightforward. While this seems enough to run cabal gen-bounds from a bash shell in the absence of a Stack-independent GHC installation...
PATH=$PATH:$(stack path --compiler-bin) cabal gen-bounds
... I couldn't figure out how to get it to follow the version restrictions of the Stack(age) snapshot -- in particular, the --package-db option, which can be helpful with commands such as cabal configure, doesn't seem to be accepted by gen-bounds.
As I don't know how to make cabal gen-bounds and Stack cooperate, I will suggest a somewhat more convoluted method, but one that doesn't require using cabal-install directly. It uses Jenga, a tool that can retrieve the version information left implicit by your choice of Stackage snapshot. Jenga is not on Stackage; to install it with Stack, grab the sources from GitHub (or with stack unpack jenga) and then run stack init --solver followed by stack install.
Remove all version bounds from the hierarchy.cabal file (or whatever the relevant .cabal file is).
stack init --solver, to create a stack.yaml file with any extra-deps that might be necessary. (You can use --resolver to explicitly choose the snapshot to be used.)
stack build, as a sanity check that the package is buildable.
In the generated stack.yaml, check whether the extra-deps field is commented out; if so, uncomment it. This is necessary for step #6 to work.
jenga -i hierarchy.cabal, which will print the exact dependency versions Stack would use to build the package.
Paste the versions Jenga gave you into the build-depends of the .cabal file, adjusting then if desired (at a minimum, you'll probably want to relax the minor version bounds for PVP compliance -- e.g. changing base == 4.9.1.0 to base == 4.9.*).
I am working on my first major Haskell application, and want to add mockery to create disposable test WAI threads. Importing mockery and running stack test resulted in the compiler error:
Failed to load interface for ‘Test.Mockery.Directory’
It is a member of the hidden package ‘mockery-0.3.5’.
Perhaps you need to add ‘mockery’ to the build-depends in your .cabal file.
Use -v to see a list of the files searched for.
So, I added mockery to my cabal file under test dependencies. However, when I run stack build or stack test mockery is automatically removed from the cabal file.
I have also tried listing mockery-0.3.5 under extra-deps in the stack.yaml file. This unsurprisingly didn't work, since mockery is part of my lts, and extra deps is for packages outside of lts.
How can I get stack to recognize that mockery should be included as a dependency to to project?
Here is my stack.yaml:
flags: {}
ghc-options:
! '*': -Wall
packages:
- .
extra-deps: [
]
resolver: lts-9.5
I'm using stack version 1.5.1
I imagine this is a stupid build issue and look forward to confronting my obvious oversight.
In stack.yaml you declare the Stackage LTS version, a curated list of hackage dependencies that you want to depend on. You can also depend on local packages and packages in git that are not in Hackage. You may also change the versions of the packages in LTS as long as they respect the constraints of the other dependencies.
package.yaml is the build file. Any packages you want to import directly in your Haskell code must be declared in here as dependencies, even if they are explicitly declared in the stack.yaml.
Finally, when you see It is a member of the hidden package, that means that one of your dependencies is using that package, but it is not declared as a dependency in your build file.
This is my stack.yaml file declaring hspec as a extra dependency:
# Specifies the GHC version and set of packages available (e.g., lts-3.5, nightly-2015-09-21, ghc-7.10.2)
resolver: lts-3.8
# Local packages, usually specified by relative directory name
packages:
- '.'
# Packages to be pulled from upstream that are not in the resolver (e.g., acme-missiles-0.3)
extra-deps:
- hspec-2.2.0
when I run stack solver it says there is no change to be done:
root#5d7daa2aec0a:/src/test_stack/a-test/src# stack solver
This command is not guaranteed to give you a perfect build plan
It's possible that even with the changes generated below, you will still need to do some manual tweaking
Asking cabal to calculate a build plan, please wait
No needed changes found
To automatically modify your stack.yaml file, rerun with '--modify-stack-yaml'
this is my source file (only to check that I could use Hspec with stack):
module Main where
import Test.Hspec
main :: IO ()
main = do
putStrLn "hello world"
and when I run stack build I get:
2015-10-05 22:24:08.450413: [warn] Could not find module `Test.Hspec' #(stack_Bp003b8iWaELtdr693pSPs:Stack.Build.Execute src/Stack/Build/Execute.hs:1241:35)
I thought stack solver was ensuring that extra dependencies are ok.
What I am doing wrong ?
It's the first time I use stack.
While stack replaces cabal-install, the command line tool for building and installing packages, it still uses the Cabal packaging infrastructure. In particular, that means projects built with stack are still Cabal-compatible packages with .cabal files, and all of their dependencies should be listed in the build-depends section of the .cabal file with appropriate version ranges. That holds even if the dependency is also specified in the stack.yaml file extra-deps field, as that field serves a different purpose (namely, giving stack an exact version to use when building the package).