This project is a dynamic template for a modern Haskell development environment. With a single command it bootstraps a haskell.nix project, shell with rich ecosystem (hlint, ghcid), out of the box support for profiling, Emacs integration and many more.
- Latests building environment
- GHC (8.10.2)
- Cabal (3.2.0.0)
- ghcid
- Linter support
- hlint (3.2.1)
- apply-refact
- pointfree
- weeder (2.1.3)
- Formatters
- stylish-haskell (0.12.2.0)
- cabal-fmt
- Testing environment for both unit and property-based tests
- hspec
- hedgehog
- Other
- local Hoogle server
- direnv
- sleek Emacs integration
pre-requirement: you have Nix installed on your system
nix-shell -p cookiecutter git --run 'cookiecutter gh:EncodePanda/haskell-starter-kit
Reentering the defaults (like github user name) might be tedious and boring. That's why it is a good practice to setup the defaults.
Modify ~/.cookiecutterrc by providing default value for github user and author name.
In my case this is:
default_context:
"gh_user": "EncodePanda"
"author_name": "Paweł Szulc"
➜ ~ nix-shell -p cookiecutter git --run 'cookiecutter gh:EncodePanda/haskell-template-project'
You've downloaded /Users/rabbit/.cookiecutters/haskell-template-project before. Is it okay to delete and re-download it? [yes]:
project_name [Enter project name]: foo
project_synopsis [Enter project synopsis]: Example project
module [Foo]:
category [Unclassified]: Example
author_name [Paweł Szulc]:
gh_user [EncodePanda]:
formatter_indent [2]:
formatter_columns [110]: 80
note: Before entering the nix-shell consider reading README.md, there is a section about using Nix cache - so that you don't have to recompile the whole world
➜ ~ cd foo
➜ foo nix-shell
trace: gitSource.nix: /Users/rabbit/foo does not seem to be a git repository,
assuming it is a clean checkout.
trace: Using latest index state for foo!
(...)
trace: Using latest index state for cabal-install!
trace: Using index-state: 2020-09-14T00:00:00Z for cabal-install
[nix-shell:~/foo]$ cabal build
Resolving dependencies...
Build profile: -w ghc-8.10.2 -O1
(...)
Building library for foo-0.1.0.0..
[1 of 1] Compiling Lib ( src/Lib.hs, /Users/rabbit/foo/dist-newstyle/build/x86_64-osx/ghc-8.10.2/foo-0.1.0.0/build/Lib.o, /Users/rabbit/foo/dist-newstyle/build/x86_64-osx/ghc-8.10.2/foo-0.1.0.0/build/Lib.dyn_o )
(...)
[1 of 1] Compiling Main ( app/Main.hs, /Users/rabbit/foo/dist-newstyle/build/x86_64-osx/ghc-8.10.2/foo-0.1.0.0/x/foo-exe/build/foo-exe/foo-exe-tmp/Main.o )
Linking /Users/rabbit/foo/dist-newstyle/build/x86_64-osx/ghc-8.10.2/foo-0.1.0.0/x/foo-exe/build/foo-exe/foo-exe ...
[nix-shell:~/foo]$ cabal test --test-show-details=streaming
Build profile: -w ghc-8.10.2 -O1
(...)
Running 1 test suites...
Test suite foo-test: RUNNING...
Foo.Example
unit tests
should work
hedgehog property tests
should work
Finished in 0.0022 seconds
2 examples, 0 failures
Test suite foo-test: PASS
Test suite logged to:
1 of 1 test suites (1 of 1 test cases) passed.
look for issues, non found
[nix-shell:~/foo]$ hlint-all
No hints
introduce code that is not perfect
[nix-shell:~/foo]$ echo "foo :: String -> Int" >> src/Lib.hs; echo "foo = \_ -> 10" >> src/Lib.hs
[nix-shell:~/foo]$ cat src/Lib.hs
module Lib where
foo :: String -> Int
foo = \_ -> 10
look for issues one more time, found it!
[nix-shell:~/foo]$ hlint-all
src/Lib.hs:3:1-14: Warning: Redundant lambda
Found:
foo = \ _ -> 10
Perhaps:
foo _ = 10
src/Lib.hs:3:7-14: Suggestion: Use const
Found:
\ _ -> 10
Perhaps:
const 10
2 hints
ask linter to automatically fix them
[nix-shell:~/foo]$ hlint-all-fix
[nix-shell:~/foo]$ cat src/Lib.hs
module Lib where
foo :: String -> Int
foo _ = 10
[nix-shell:~/foo]$ hlint-all
No hints
[nix-shell:~/projects/Foo]$ ghcid
Loading cabal repl ...
Build profile: -w ghc-8.10.1 -O1
In order, the following will be built (use -v for more details):
- Foo-0.1.0.0 (lib) (ephemeral targets)
Preprocessing library for Foo-0.1.0.0..
GHCi, version 8.10.1: https://www.haskell.org/ghc/ :? for help
[1 of 1] Compiling Lib ( src/Lib.hs, interpreted )
Ok, one module loaded.
All good (1 module, at 23:56:46)
[nix-shell:~/projects/foo]$ hoogle server --local
Server started on port 8080
Reading log...0.00s
2021-01-05T15:39:39.488174 - Server starting on port 8080 and host/IP Host "127.0.0.1"
You can use pointfree in the shell
[nix-shell:~/projects/foo]$ pointfree "foo list = fmap (+1) list"
foo = fmap (1 +)
or you can use it in the REPL
[nix-shell:~/projects/foo]$ cabal repl
Loaded GHCi configuration from /Users/rabbit/projects/foo/.ghci
[1 of 1] Compiling Lib ( src/Lib.hs, interpreted )
Ok, one module loaded.
λ> :pf foo list = fmap (+1) list
foo = fmap (1 +)
*Lib
[nix-shell:~/projects/foo]$ weeder
Weeds detected: 0
[nix-shell:~/projects/foo]$ echo "notUsed :: Int" >> src/Lib.hs
[nix-shell:~/projects/foo]$ echo "notUsed = 10" >> src/Lib.hs
[nix-shell:~/projects/foo]$ cat src/Lib.hs
module Lib where
notUsed :: Int
notUsed = 10
[nix-shell:~/projects/foo]$ cabal build
(...)
Preprocessing executable 'foo-exe' for foo-0.1.0.0..
Building executable 'foo-exe' for foo-0.1.0.0..
(...)
Linking ~/projects/foo/dist-newstyle/build/x86_64-osx/ghc-8.10.2/
[nix-shell:~/projects/foo]$ weeder
src/Lib.hs:3:1: error: notUsed is unused
1 ┃ module Lib where
2 ┃ notUsed :: Int
3 ┃ notUsed = 10
Delete this definition or add ‘Lib.notUsed’ as a root to fix this error.
Weeds detected: 1