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haskell: Clean up README

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Eivind Fonn 2016-05-06 13:24:12 +02:00
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@ -24,28 +24,28 @@
- [[Cabal commands][Cabal commands]] - [[Cabal commands][Cabal commands]]
- [[Cabal files][Cabal files]] - [[Cabal files][Cabal files]]
- [[Ghc-mod][Ghc-mod]] - [[Ghc-mod][Ghc-mod]]
- [[insert template][insert template]] - [[Insert template][Insert template]]
- [[Syntax checking][Syntax checking]] - [[Syntax checking][Syntax checking]]
- [[Flycheck ][Flycheck ]] - [[Flycheck ][Flycheck ]]
- [[HLint][HLint]] - [[HLint][HLint]]
- [[ghc-mod][ghc-mod]] - [[ghc-mod][ghc-mod]]
- [[Haskell-mode interactive][Haskell-mode interactive]] - [[Interactive haskell-mode][Interactive haskell-mode]]
- [[Flymake][Flymake]] - [[Flymake][Flymake]]
- [[Troubles shooting][Troubles shooting]] - [[Troublesshooting][Troublesshooting]]
- [[FAQ][FAQ]] - [[FAQ][FAQ]]
- [[REPL doesn't work][REPL doesn't work]] - [[The REPL doesn't work][The REPL doesn't work]]
- [[REPL is stuck][REPL is stuck]] - [[The REPL is stuck][The REPL is stuck]]
- [[I am using =stack= and =ghc-mod=, but =ghc-mod= doesn't work][I am using =stack= and =ghc-mod=, but =ghc-mod= doesn't work]] - [[I am using =stack= and =ghc-mod=, but =ghc-mod= doesn't work][I am using =stack= and =ghc-mod=, but =ghc-mod= doesn't work]]
- [[Indentation doesn't reset when pressing return after empty line][Indentation doesn't reset when pressing return after empty line]] - [[Indentation doesn't reset when pressing return after an empty line][Indentation doesn't reset when pressing return after an empty line]]
- [[Flycheck displays HLInt warnings but not errors][Flycheck displays HLInt warnings but not errors]] - [[Flycheck displays HLInt warnings but not errors][Flycheck displays HLInt warnings but not errors]]
- [[I can see highlighted errors but they don't appear in the errors list][I can see highlighted errors but they don't appear in the errors list]] - [[I can see highlighted errors but they don't appear in the error list][I can see highlighted errors but they don't appear in the error list]]
- [[Flycheck doesn't work][Flycheck doesn't work]] - [[Flycheck doesn't work][Flycheck doesn't work]]
- [[Flycheck doesn't work with =stack=][Flycheck doesn't work with =stack=]] - [[Flycheck doesn't work with =stack=][Flycheck doesn't work with =stack=]]
- [[stack build directory is wrong][stack build directory is wrong]] - [[The stack build directory is wrong][The stack build directory is wrong]]
- [[Project root directory not set properly][Project root directory not set properly]] - [[The Project root directory is not set properly][The Project root directory is not set properly]]
- [[haskell-mode commands don't work ][haskell-mode commands don't work ]] - [[haskell-mode commands don't work ][haskell-mode commands don't work ]]
- [[=ghc-mod= and =haskell-mode= commands overlaps. How do I know which command belongs to what ?][=ghc-mod= and =haskell-mode= commands overlaps. How do I know which command belongs to what ?]] - [[=ghc-mod= and =haskell-mode= commands overlap. How do I know which command belongs to what?][=ghc-mod= and =haskell-mode= commands overlap. How do I know which command belongs to what?]]
- [[Some commands start with =ghc-= and some with =haskell-=. What does that mean ?][Some commands start with =ghc-= and some with =haskell-=. What does that mean ?]] - [[Some commands start with =ghc-= and some with =haskell-=. What does that mean?][Some commands start with =ghc-= and some with =haskell-=. What does that mean?]]
* Description * Description
This layer adds support for the [[https://www.haskell.org/][Haskell]] language. This layer adds support for the [[https://www.haskell.org/][Haskell]] language.
@ -108,9 +108,8 @@ the project root. As it will confuse =ghc-mod=. For more troubleshooting,
checkout this [[https://github.com/kazu-yamamoto/ghc-mod/wiki#known-issues-related-to-stack][document]]. checkout this [[https://github.com/kazu-yamamoto/ghc-mod/wiki#known-issues-related-to-stack][document]].
*** Stack users *** Stack users
From time to time =ghc-mod= is not available via latest Stackage LTS version. So
Time to time =ghc-mod= is not available via latest Stackage LTS version. So if if you have problems with calling =stack install ghc-mod=, try to use =stack
you have problems with calling =stack install ghc-mod=, try to use =stack
install ghc-mod --resolver lts-3.1= (the last known LTS version that had install ghc-mod --resolver lts-3.1= (the last known LTS version that had
=ghc-mod=). But even if it doesn't work, don't panic, it's easy to install it =ghc-mod=). But even if it doesn't work, don't panic, it's easy to install it
from sources. from sources.
@ -143,23 +142,23 @@ $ rm -rf ghc-mod
#+END_SRC #+END_SRC
** Optional extras ** Optional extras
The Haskell layer supports some extra features that can be enabled through The Haskell layer supports some extra features that can be enabled through layer
layer variables. variables.
*** GHCi-ng support *** GHCi-ng support
[[https://github.com/chrisdone/ghci-ng][ghci-ng]] adds some nice features to =haskell-mode=, and is supported in [[https://github.com/chrisdone/ghci-ng][ghci-ng]] adds some nice features to =haskell-mode=, and is supported in Spacemacs
Spacemacs by a layer variable: by a layer variable:
Follow the instructions to install [[https://github.com/chrisdone/ghci-ng][ghci-ng]] (remember to add =:set +c= Follow the instructions to install [[https://github.com/chrisdone/ghci-ng][ghci-ng]] (remember to add =:set +c= in
in =~/.ghci=), next set the layer variable: =~/.ghci=), next set the layer variable:
#+BEGIN_SRC emacs-lisp #+BEGIN_SRC emacs-lisp
(setq-default dotspacemacs-configuration-layers (setq-default dotspacemacs-configuration-layers
'((haskell :variables haskell-enable-ghci-ng-support t))) '((haskell :variables haskell-enable-ghci-ng-support t)))
#+END_SRC #+END_SRC
Once ghci-ng is enabled, two of the old keybindings are overriden with Once ghci-ng is enabled, two of the old keybindings are overriden with improved
improved versions from ghci-ng, and a new keybinding available: versions from ghci-ng, and a new keybinding available:
| Key Binding | Description | | Key Binding | Description |
|-------------+---------------------------------------------------------------------------| |-------------+---------------------------------------------------------------------------|
@ -168,7 +167,6 @@ improved versions from ghci-ng, and a new keybinding available:
| ~SPC m u~ | finds uses of identifier | | ~SPC m u~ | finds uses of identifier |
**** Stack users **** Stack users
=Stack= and =ghci-ng= doesn't play well with each other, so the general advice =Stack= and =ghci-ng= doesn't play well with each other, so the general advice
is to avoid mixing them. But, if you want mix them anyway, you'll need to set is to avoid mixing them. But, if you want mix them anyway, you'll need to set
=haskell-process-type= explicitly: =haskell-process-type= explicitly:
@ -186,8 +184,7 @@ if you have =stack.yaml= file in the root of your project, =stack-ghci= will be
used as process type. used as process type.
**** ghc-mod users **** ghc-mod users
If you want to use ~SPC m h t~ from =ghc-mod= instead of =ghci-ng=, then you
If you want to use ~SPC m h t~ from =ghc-mod= instead of =ghci-ng= - then you
need to add following line in your =dotspacemacs/user-config=: need to add following line in your =dotspacemacs/user-config=:
#+BEGIN_SRC emacs-lisp #+BEGIN_SRC emacs-lisp
@ -199,8 +196,8 @@ This might be useful, because =ghc-mod= doesn't require active REPL in order to
get type of symbol. get type of symbol.
*** structured-haskell-mode *** structured-haskell-mode
[[https://github.com/chrisdone/structured-haskell-mode][structured-haskell-mode]], or shm, replaces default haskell-mode [[https://github.com/chrisdone/structured-haskell-mode][structured-haskell-mode]], or shm, replaces default haskell-mode auto-indentation
auto-indentation and adds some nice functionalities. and adds some nice functionalities.
To install =shm= run =cabal install structured-haskell-mode= (or =stack= To install =shm= run =cabal install structured-haskell-mode= (or =stack=
equivalent). equivalent).
@ -226,22 +223,22 @@ For a nice visualization of these functions, please refer to the github page
for [[https://github.com/chrisdone/structured-haskell-mode#features][structured-haskell-mode]]. for [[https://github.com/chrisdone/structured-haskell-mode#features][structured-haskell-mode]].
*Warning* structured-haskell-mode doesn't play very well with =evil= *Warning* structured-haskell-mode doesn't play very well with =evil=
([[https://github.com/chrisdone/structured-haskell-mode/issues/81][structured-haskell-mode/#81]]). So it's better to be used with =emacs= edit ([[https://github.com/chrisdone/structured-haskell-mode/issues/81][structured-haskell-mode/#81]]). So it's recommended only to be used with the
style. =emacs= editing style.
*** hindent *** hindent
[[https://github.com/chrisdone/hindent][hindent]] is an extensible Haskell pretty printer, which let's you [[https://github.com/chrisdone/hindent][hindent]] is an extensible Haskell pretty printer, which let's you
reformat your code. You need to install the executable with =cabal reformat your code. You need to install the executable with =cabal
install hindent= or =stack install hindent= install hindent= or =stack install hindent=
To enable it you have to set the variable =haskell-enable-hindent-style= To enable it you have to set the variable =haskell-enable-hindent-style= to a
to a supported style. The available styles are: supported style. The available styles are:
- fundamental - fundamental
- johan-tibell - johan-tibell
- chris-done - chris-done
- gibiansky - gibiansky
See examples [[https://github.com/chrisdone/hindent#example][here]] See examples [[https://github.com/chrisdone/hindent#example][here]].
#+BEGIN_SRC emacs-lisp #+BEGIN_SRC emacs-lisp
(setq-default dotspacemacs-configuration-layers (setq-default dotspacemacs-configuration-layers
@ -349,59 +346,66 @@ ghc-mod commands are prefixed by ~SPC m m~:
| ~SPC m m >~ | make indent deeper | | ~SPC m m >~ | make indent deeper |
| ~SPC m m <~ | make indent shallower | | ~SPC m m <~ | make indent shallower |
*** insert template *** Insert template
~SPC m m t~ inserts a template. What this means is that ~SPC m m t~ inserts a template. What this means is that in the beginning of a
In the beginning of a buffer, "module Foo where" is buffer, =module Foo where= is inserted. On a function without signature, the
inserted. On the function without signature, inferred inferred type is inserted. On a symbol =foo= without definition, =foo =
type is inserted. On a symbol "foo" without definition, undefined= is inserted or a proper module is imported. ~SPC m m u~ inserts a
"foo = undefined" is inserted or a proper module is imported. hole in this case. On a variable, the case is split. When checking with hlint,
~SPC m m u~ inserts a hole in this case. On a variable, original code is replaced with hlint's suggestion if possible.
the case is split. When checking with hlint, original code
is replaced with hlint's suggestion if possible.
* Syntax checking * Syntax checking
At the moment there are 4 components which can check the syntax and indicates somehow error and warnings in the code. At the moment there are four components which can check the syntax and indicates
Those components are : somehow error and warnings in the code. Those components are
- flycheck
- flycheck - hlint (via flycheck)
- hlint (via flycheck) - ghc-mod
- ghc-mod - haskell-mode interactive
- haskell-mode interactive
As all those components can be active at the same time, it can be tricky to know which component is display which message, As all these components can be active at the same time, it can be tricky to know
especially when they disagree or one is not working. Only flycheck errors (ghc and hlint) are displayed in the error list and which component is displaying which message, especially when they disagree or
can be navigated using the standard spacemacs key bindings even though errors from other mode might highlight error in the buffer. one is not working. Only flycheck errors (ghc and hlint) are displayed in the
error list and can be navigated using the standard spacemacs key bindings (under
~SPC e~) even though errors from other modes might highlight the actual buffer.
** Flycheck ** Flycheck
This is the standard spacemacs way to do syntax checking and the most elaborate. flyckeck displays errors, warning, info, including symbols on the left or right side of the buffer This is the standard spacemacs way to do syntax checking and the most elaborate.
and tooltips if possible. You need the syntax-checking layer to enable this. Please the documentation for
Errors are also available in the error window (~SPC e l~) and you can navigate between errors using ~SPC e n~ and ~SPC e p~. that layer on how to interact with flycheck.
Flycheck can be toggle on/off with ~SPC t s~.
Flycheck has different haskell checker : haskell-ghc, haskell-stackghc and haskell-hlint. Flycheck has different Haskell checkers: =haskell-ghc=, =haskell-stackghc= and
It normally detect automatically the good one, but if it doesn't work, you can change it using =flycheck-select-checker= (~SPC e s~). =haskell-hlint=. Normally it can automatically detect the best one to use, but
if it doesn't work, you can change it using ~SPC e s~.
** HLint ** HLint
HLint is a linter for Haskell. It doesn't detect error (as long as it can parse the file) but detect bad coding style and code smell. HLint is a linter for Haskell. It doesn't detect errors (as long as it can parse
HLint checker is called *after* the flycheck ghc checker. the file) but bad coding style and code smell. The HLint checker is called
*after* the flycheck GHC checker.
** ghc-mod ** ghc-mod
ghc-mod when enabled, does also syntax checking. It doesn't highlight errors but instead displays a ! in the left band. Ghc-mod, when enabled, also does syntax checking. It doesn't highlight errors
You can navigate between errors using =ghc-goto-next-error= (~M-n)~ and =ghc-goto-prev-error= (~M-p~). but instead displays an exclamation point in the fringe. You can navigate
between errors using =ghc-goto-next-error= (~M-n~) and =ghc-goto-prev-error=
** Haskell-mode interactive (~M-p~).
Finally, haskell-mode when in interactive (~SPC m s b~) also displays errors.
haskell-mode errors can be navigated from the interactive buffer (by clicking on the error) or using
=haskell-goto-next-error= (~M-n~) and =haskell-goto-prev-error= (~M-p~) (same binding as ghc-mod).
** Interactive haskell-mode
Finally, interactive haskell-mode (~SPC m s b~) also displays errors. These
errors can be navigated from the interactive buffer (by clicking on the error)
or using =haskell-goto-next-error= (~M-n~) and =haskell-goto-prev-error=
(~M-p~).
** Flymake ** Flymake
An alternative to syntax checking is to build your project using =flymake-compile=. It doesn't highlight the error on the buffer but is more reliable. An alternative to syntax checking is to build your project using
Error navigation is similar to haskell-mode interactive. =flymake-compile=. It doesn't highlight error in the buffer but is more
** Troubles shooting reliable. The error navigation is similar to interactive haskell-mode.
Flycheck and ghc-mod can fails silently for miscellaneous reasons. See the [[FAQ]] for trouble shootings.
** Troublesshooting
Flycheck and ghc-mod can fail silently for miscellaneous reasons. See the [[FAQ]]
for troubleshooting.
* FAQ * FAQ
** REPL doesn't work ** The REPL doesn't work
Usually =haskell-mode= is great at figuring out which interactive process to Usually =haskell-mode= is great at figuring out which interactive process to
bring up. But if you are experiencing problems with it you can help bring up. But if you are experiencing problems with it you can help
=haskell-mode= by setting =haskell-process-type= as in following code: =haskell-mode= by setting =haskell-process-type= as in following code:
@ -419,7 +423,7 @@ Available options are:
- cabal-ghci - cabal-ghci
- stack-ghci - stack-ghci
** REPL is stuck ** The REPL is stuck
Make sure that when you are typing anything in REPL there is a space between Make sure that when you are typing anything in REPL there is a space between
what you type and =λ>=. When there is no space - REPL will behave as it's stuck. what you type and =λ>=. When there is no space - REPL will behave as it's stuck.
Usually, when you enter normal state, cursor is moved back, so there is no Usually, when you enter normal state, cursor is moved back, so there is no
@ -450,9 +454,11 @@ could place following snippet in your =dotspacemacs/user-config= function:
** I am using =stack= and =ghc-mod=, but =ghc-mod= doesn't work ** I am using =stack= and =ghc-mod=, but =ghc-mod= doesn't work
Make sure that =dist= directory doesn't exist in your project root. So if it Make sure that =dist= directory doesn't exist in your project root. So if it
exists, just remove it and try again. exists, just remove it and try again.
** Indentation doesn't reset when pressing return after empty line
This is intended behavior in =haskell-indentation-mode=. If you want to reset indentation when pressing return after empty line, add following snippet into your =dotspacemacs/user-config= function. ** Indentation doesn't reset when pressing return after an empty line
This is the intended behavior in =haskell-indentation-mode=. If you want to
reset indentation when pressing return after an empty line, add the following
snippet into your =dotspacemacs/user-config= function.
#+BEGIN_SRC emacs-lisp #+BEGIN_SRC emacs-lisp
(defun haskell-indentation-advice () (defun haskell-indentation-advice ()
@ -465,45 +471,54 @@ This is intended behavior in =haskell-indentation-mode=. If you want to reset in
(advice-add 'haskell-indentation-newline-and-indent (advice-add 'haskell-indentation-newline-and-indent
:after 'haskell-indentation-advice) :after 'haskell-indentation-advice)
#+END_SRC #+END_SRC
** Flycheck displays HLInt warnings but not errors ** Flycheck displays HLInt warnings but not errors
HLint checker is called *after* normal flycheck checker even if the checkers fails. Check the [[Flycheck doesn't work]] section. The HLint checker is called *after* normal flycheck checker even if the checker
** I can see highlighted errors but they don't appear in the errors list fails. Check the [[Flycheck doesn't work]] section.
The errors list is only set by flycheck. You are probably seeing highlightings coming from either ghc-mode or haskell-mode.
Check the [[Flycheck doesn't work]] section. ** I can see highlighted errors but they don't appear in the error list
The error list is only set by flycheck. You are probably seeing errors
highlighted by either ghc-mode or haskell-mode. Check the [[Flycheck doesn't work]]
section.
** Flycheck doesn't work ** Flycheck doesn't work
You can check what is wrong with flycheck with the =flycheck-compile= command. You can check what is wrong with flycheck with the =flycheck-compile= command.
This will show you the exact command line used and its output. This will show you the exact command line used and its output.
If you are using stack, check the [[Flycheck doesn't work with =stack=]] section. If you are using stack, check the [[Flycheck doesn't work with =stack=]] section.
** Flycheck doesn't work with =stack= ** Flycheck doesn't work with =stack=
First check flycheck use the correct checker and all the path are properly configured using =flycheck-verify-setup= (~SPC e v~). First check that flycheck uses the correct checker and all the paths are
You can force the checker by using =flycheck-select-checker= (~SPC e s~) to =haskell-stack-ghc=. properly configured using =flycheck-verify-setup= (~SPC e v~). You can force the
If it still doesn't work, it could be one of the following problems : checker with =flycheck-select-checker= (~SPC e s~) to ensure it uses
=haskell-stack-ghc=. If it still doesn't work, it could be one of the following
problems:
- stack build directory is wrong. - The stack build directory is wrong
- project root not set properly - The project root is not set properly
*** The stack build directory is wrong
The path to the build directory containing some generated files is normally
under =.stack-work/install/<os>/Cabal-<version>/build=.
*** stack build directory is wrong However, the version of the cabal library used by stack to generate the
The path to the build directory containing some generated files is normally under directory name is not the version of the cabal library installed by stack, but
the version of cabal associated to the GHC version. This error can happen after
upgrading cabal or cabal-install. To check if this is the problem, compare the
path name of the build path used by flycheck using =flycheck-compile= and
compare it to to the actual path in the =.stack-work= directory. If they are
different you need to reinstall ghc using the command =stack setup
--upgrade-cabal=.
=.stack-work/install/<os>/Cabal-<version/build=. *** The Project root directory is not set properly
Flycheck launches the GHC command not from the project root directory but from
the the directory of the file being checked. This is normally not a problem as
all the paths are set properly, however it could be a problem if some template
Haskell functions use relative paths (e.g. in Yesod scaffolded projects).
However, the version of the cabal library used by stack to generate the directory name is not Until it's fixed in flycheck the workaround is to the wrap the stack command to
the version of the cabal library installed by stack, but the version of cabal associated to the ghc version. run all subcommands from the project root directory. You can do so with the
This error can happen after upgrading cabal or cabal-install. following script:
To check if it's the problem, look at path name of the build pathn used by flycheck using =flycheck-compile= and compare it to
to the actual name path in the =.stack-work= directory. If they mismatch you need to reinstall ghc using the command
=stack setup --upgrade-cabal=.
*** Project root directory not set properly
Flycheck launch the ghc command not from the project root directory but from the the directory of the file being checked.
This is not normally a problem as all the paths are set properly. However it could be a problem if some template haskell
function uses relative paths (as found in Yesod scaffholded projects).
Until it's fixed in flycheck the alternative is to the wrap the stack command to run all subcommand from the project root directory. You can do so with the following script:
#+BEGIN_SRC bash #+BEGIN_SRC bash
#!/bin/bash #!/bin/bash
@ -511,16 +526,17 @@ cd `stack --project-root`
stack $* stack $*
#+END_SRC #+END_SRC
and set the =flycheck-haskell-stack-ghc-executable= to it. Make sure you set =flycheck-haskell-stack-ghc-executable= to this script.
** haskell-mode commands don't work ** haskell-mode commands don't work
Some (most of) haskell-mode commands only works when haskell-mode is in interactive mode, .i.e as a interactive session associated to it. Some (most of) the haskell-mode commands only works when haskell-mode is in
Load the buffer using ~SPC m s b~. interactive mode, i.e. as a interactive session associated to it. Load it using
** =ghc-mod= and =haskell-mode= commands overlaps. How do I know which command belongs to what ? ~SPC m s b~.
ghc-mod commands are prefixed with =ghc-=, haskell-mode ones are prefixed with =haskell-=.
** Some commands start with =ghc-= and some with =haskell-=. What does that mean ?
Commands starting with =ghc-= are ghc-mod commands.
Commands starting with =haskell-= are haskell-mode.
** =ghc-mod= and =haskell-mode= commands overlap. How do I know which command belongs to what?
ghc-mod commands are prefixed with =ghc-=, haskell-mode ones are prefixed with
=haskell-=.
** Some commands start with =ghc-= and some with =haskell-=. What does that mean?
Commands starting with =ghc-= are ghc-mod commands. Commands starting with
=haskell-= are haskell-mode commands.