Add ormolu fixer.

This commit adds a fixer for the Haskell language, ormolu
(https://github.com/tweag/ormolu).

Signed-off-by: David Wood <david@davidtw.co>

7 files changed, 64 insertions, 0 deletions

diff --git a/autoload/ale/fix/registry.vim b/autoload/ale/fix/registry.vim
index d71668f2..377edafd 100644
--- a/autoload/ale/fix/registry.vim
+++ b/autoload/ale/fix/registry.vim
@@ -380,6 +380,11 @@ let s:default_registry = {
 \       'suggested_filetypes': ['dhall'],
 \       'description': 'Fix Dhall files with dhall-format.',
 \   },
+\   'ormolu': {
+\       'function': 'ale#fixers#ormolu#Fix',
+\       'suggested_filetypes': ['haskell'],
+\       'description': 'A formatter for Haskell source code.',
+\   },
 \}
 
 " Reset the function registry to the default entries.
diff --git a/autoload/ale/fixers/ormolu.vim b/autoload/ale/fixers/ormolu.vim
new file mode 100644
index 00000000..69b55c1f
--- /dev/null
+++ b/autoload/ale/fixers/ormolu.vim
@@ -0,0 +1,12 @@
+call ale#Set('haskell_ormolu_executable', 'ormolu')
+call ale#Set('haskell_ormolu_options', '')
+
+function! ale#fixers#ormolu#Fix(buffer) abort
+    let l:executable = ale#Var(a:buffer, 'haskell_ormolu_executable')
+    let l:options = ale#Var(a:buffer, 'haskell_ormolu_options')
+
+    return {
+    \   'command': ale#Escape(l:executable)
+    \       . (empty(l:options) ? '' : ' ' . l:options),
+    \}
+endfunction
diff --git a/doc/ale-haskell.txt b/doc/ale-haskell.txt
index 5dd3ec15..fde439fe 100644
--- a/doc/ale-haskell.txt
+++ b/doc/ale-haskell.txt
@@ -173,4 +173,24 @@ g:ale_haskell_hie_executable                     *g:ale_haskell_hie_executable*
 
 
 ===============================================================================
+ormolu                                                     *ale-haskell-ormolu*
+
+g:ale_haskell_ormolu_executable               *g:ale_haskell_ormolu_executable*
+                                              *b:ale_haskell_ormolu_executable*
+  Type: |String|
+  Default: `'ormolu'`
+
+  This variable can be changed to use a different executable for ormolu.
+
+
+g:ale_haskell_ormolu_options                     *g:ale_haskell_ormolu_options*
+                                                 *b:ale_haskell_ormolu_options*
+  Type: String
+  Default: ''
+
+  This variable can be used to pass extra options to the underlying ormolu
+  executable.
+
+
+===============================================================================
   vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl:
diff --git a/doc/ale-supported-languages-and-tools.txt b/doc/ale-supported-languages-and-tools.txt
index 4f3afd85..57a50dd4 100644
--- a/doc/ale-supported-languages-and-tools.txt
+++ b/doc/ale-supported-languages-and-tools.txt
@@ -195,6 +195,7 @@ Notes:
   * `hie`
   * `hindent`
   * `hlint`
+  * `ormolu`
   * `stack-build`!!
   * `stack-ghc`
   * `stylish-haskell`
diff --git a/doc/ale.txt b/doc/ale.txt
index eb8f0275..01357cd1 100644
--- a/doc/ale.txt
+++ b/doc/ale.txt
@@ -2642,6 +2642,7 @@ documented in additional help files.
     stack-ghc.............................|ale-haskell-stack-ghc|
     stylish-haskell.......................|ale-haskell-stylish-haskell|
     hie...................................|ale-haskell-hie|
+    ormolu................................|ale-haskell-ormolu|
   hcl.....................................|ale-hcl-options|
     terraform-fmt.........................|ale-hcl-terraform-fmt|
   html....................................|ale-html-options|
diff --git a/supported-tools.md b/supported-tools.md
index 49460892..6aa196b2 100644
--- a/supported-tools.md
+++ b/supported-tools.md
@@ -204,6 +204,7 @@ formatting.
   * [hie](https://github.com/haskell/haskell-ide-engine)
   * [hindent](https://hackage.haskell.org/package/hindent)
   * [hlint](https://hackage.haskell.org/package/hlint)
+  * [ormolu](https://github.com/tweag/ormolu)
   * [stack-build](https://haskellstack.org/) :floppy_disk:
   * [stack-ghc](https://haskellstack.org/)
   * [stylish-haskell](https://github.com/jaspervdj/stylish-haskell)
diff --git a/test/fixers/test_ormolu_fixer_callback.vader b/test/fixers/test_ormolu_fixer_callback.vader
new file mode 100644
index 00000000..8df3fca9
--- /dev/null
+++ b/test/fixers/test_ormolu_fixer_callback.vader
@@ -0,0 +1,24 @@
+Before:
+  Save g:ale_haskell_ormolu_executable
+  Save g:ale_haskell_ormolu_options
+
+After:
+  Restore
+
+Execute(The ormolu callback should return the correct default values):
+  AssertEqual
+  \ {
+  \   'command': ale#Escape('ormolu')
+  \ },
+  \ ale#fixers#ormolu#Fix(bufnr(''))
+
+Execute(The ormolu executable and options should be configurable):
+  let g:ale_nix_nixpkgsfmt_executable = '/path/to/ormolu'
+  let g:ale_nix_nixpkgsfmt_options = '-h'
+
+  AssertEqual
+  \ {
+  \   'command': ale#Escape('/path/to/ormolu')
+  \     . ' -h',
+  \ },
+  \ ale#fixers#nixpkgsfmt#Fix(bufnr(''))