feat: add Haskell list support

lua/treesj/langs/haskell.lua

@@ -0,0 +1,24 @@
+local lang_utils = require('treesj.langs.utils')
+
+return {
+  list = {
+    both = {
+      separator = ',',
+      last_separator = false,
+    },
+    split = {
+      -- Maintain necessary whitespace: https://github.com/Wansmer/treesj/discussions/163
+      format_tree = function(tsj)
+        local len = tsj:child(1):range()[2] -- index of first character of first node
+        for child in tsj:iter_children() do
+          if not (child:is_first() or child:is_omit()) then
+            local indent = not child:is_last()
+                and (' '):rep(len + vim.fn.shiftwidth())
+              or (' '):rep(len)
+            child:update_text(indent .. child:text())
+          end
+        end
+      end,
+    },
+  },
+}

lua/treesj/langs/init.lua

@@ -33,7 +33,8 @@ M.configured_langs = {
   'bash',
   'sql',
   'dart',
-  'elixir'
+  'elixir',
+  'haskell',
 }
 
 M.presets = {}

tests/langs/haskell/join_spec.lua

@@ -0,0 +1,26 @@
+local tu = require('tests.utils')
+
+local PATH = './tests/sample/index.hs'
+local LANG = 'haskell'
+
+local data_for_join = {
+  {
+    path = PATH,
+    mode = 'join',
+    lang = LANG,
+    desc = 'lang "%s", node "list", preset default',
+    cursor = { 5, 0 },
+    expected = { 1, 2 },
+    result = { 3, 4 },
+  },
+}
+
+local treesj = require('treesj')
+local opts = {}
+treesj.setup(opts)
+
+describe('TreeSJ JOIN:', function()
+  for _, value in ipairs(data_for_join) do
+    tu._test_format(value, treesj)
+  end
+end)

tests/langs/haskell/split_spec.lua

@@ -0,0 +1,26 @@
+local tu = require('tests.utils')
+
+local PATH = './tests/sample/index.hs'
+local LANG = 'haskell'
+
+local data_for_split = {
+  {
+    path = PATH,
+    mode = 'split',
+    lang = LANG,
+    desc = 'lang "%s", node "list", preset default',
+    cursor = { 2, 12 },
+    expected = { 3, 8 },
+    result = { 1, 6 },
+  },
+}
+
+local treesj = require('treesj')
+local opts = {}
+treesj.setup(opts)
+
+describe('TreeSJ SPLIT:', function()
+  for _, value in ipairs(data_for_split) do
+    tu._test_format(value, treesj)
+  end
+end)

tests/sample/index.hs

@@ -0,0 +1,8 @@
+-- RESULT OF JOIN (node "list", preset default)
+let x = [1, 2, 3]
+-- RESULT OF SPLIT (node "list", preset default)
+let x = [
+          1,
+          2,
+          3
+        ]