feat(lua): add vim.list.unique()

Problem:
No way to deduplicate values in a list in-place

Solution:
Add `vim.list.unique()`

1 files changed, 22 insertions, 0 deletions

diff --git a/test/functional/lua/vim_spec.lua b/test/functional/lua/vim_spec.lua
index 9372f5c7b7..14e08cffba 100644
--- a/test/functional/lua/vim_spec.lua
+++ b/test/functional/lua/vim_spec.lua
@@ -1260,6 +1260,28 @@ describe('lua stdlib', function()
     eq({ 2 }, exec_lua [[ return vim.list_extend({}, {2;a=1}, -1, 2) ]])
   end)
 
+  it('vim.list.unique', function()
+    eq({ 1, 2, 3, 4, 5 }, vim.list.unique({ 1, 2, 2, 3, 4, 4, 5 }))
+    eq({ 1, 2, 3, 4, 5 }, vim.list.unique({ 1, 2, 3, 4, 4, 5, 1, 2, 3, 2, 1, 2, 3, 4, 5 }))
+    eq({ 1, 2, 3, 4, 5, field = 1 }, vim.list.unique({ 1, 2, 2, 3, 4, 4, 5, field = 1 }))
+
+    -- Not properly defined, but test anyway
+    -- luajit evaluates #t as 7, whereas Lua 5.1 evaluates it as 12
+    local r = vim.list.unique({ 1, 2, 2, 3, 4, 4, 5, nil, 6, 6, 7, 7 })
+    if jit then
+      eq({ 1, 2, 3, 4, 5, nil, nil, nil, 6, 6, 7, 7 }, r)
+    else
+      eq({ 1, 2, 3, 4, 5, nil, 6, 7 }, r)
+    end
+
+    eq(
+      { { 1 }, { 2 }, { 3 } },
+      vim.list.unique({ { 1 }, { 1 }, { 2 }, { 2 }, { 3 }, { 3 } }, function(x)
+        return x[1]
+      end)
+    )
+  end)
+
   it('vim.tbl_add_reverse_lookup', function()
     eq(
       true,