feat(util): Util.merge now support advanced merging strategies. Docs coming soon

Author: folke

TODO.md

@@ -1,5 +1,10 @@
 # ✅ TODO
 
+- [ ] better merging options?
+- [ ] especially what to do with merging of handlers?
+- [ ] overwriting keymaps probably doesn't work
+- [ ] disabled deps?
+
 - [x] fancy UI to manage all your Neovim plugins
 - [x] auto lazy-loading of lua modules
 - [x] lazy-loading on events, commands, filetypes and key mappings

lua/lazy/core/plugin.lua

@@ -270,20 +270,10 @@ function Spec:merge(old, new)
 
   for _, prop in ipairs(list_merge) do
     if new[prop] and old[prop] then
-      ---@type any[]
-      local props = {}
-      ---@diagnostic disable-next-line: no-unknown
-      for _, value in ipairs(old[prop]) do
-        props[#props + 1] = value
+      if new[prop].__merge == nil then
+        new[prop].__merge = true
       end
-      ---@diagnostic disable-next-line: no-unknown
-      for _, value in ipairs(new[prop]) do
-        if not vim.tbl_contains(props, value) then
-          props[#props + 1] = value
-        end
-      end
-      ---@diagnostic disable-next-line: no-unknown
-      new[prop] = props
+      new[prop] = Util.merge(old[prop], new[prop])
     end
   end
   new._.super = old

lua/lazy/core/util.lua

@@ -286,10 +286,27 @@ function M.debug(msg, level, opts)
   end
 end
 
+local MERGE = "__merge"
+
 local function can_merge(v)
   return type(v) == "table" and (vim.tbl_isempty(v) or not M.is_list(v))
 end
 
+local function can_extend(v)
+  return type(v) == "table" and (vim.tbl_isempty(v) or M.is_list(v))
+end
+
+---@param v any|{__merge:boolean}
+---@param merge? boolean
+---@return boolean?
+local function check_merge(v, merge)
+  if type(v) == "table" and v[MERGE] ~= nil then
+    merge = v[MERGE]
+    v[MERGE] = nil
+  end
+  return merge
+end
+
 --- Merges the values similar to vim.tbl_deep_extend with the **force** behavior,
 --- but the values can be any type, in which case they override the values on the left.
 --- Values will me merged in-place in the first left-most table. If you want the result to be in
@@ -301,12 +318,24 @@ end
 function M.merge(...)
   local values = { ... }
   local ret = values[1]
+
+  if ret == vim.NIL then
+    ret = nil
+  end
+
+  local merge = check_merge(ret)
+
   for i = 2, #values, 1 do
     local value = values[i]
-    if can_merge(ret) and can_merge(value) then
+    merge = check_merge(value, merge)
+    if can_merge(ret) and can_merge(value) and merge ~= false then
       for k, v in pairs(value) do
         ret[k] = M.merge(ret[k], v)
       end
+    elseif can_extend(ret) and can_extend(value) and merge then
+      for _, v in ipairs(value) do
+        ret[#ret + 1] = v
+      end
     elseif value == vim.NIL then
       ret = nil
     else

tests/core/util_spec.lua

@@ -132,4 +132,45 @@ describe("util", function()
     assert(root, "foobar root not found")
     assert.same(Helpers.path("new/lua/foobar"), root)
   end)
+
+  it("merges correctly", function()
+    local tests = {
+      {
+        input = { { a = 1 }, { b = 2 } },
+        output = { a = 1, b = 2 },
+      },
+      {
+        input = { { a = 1 }, { a = 2 } },
+        output = { a = 2 },
+      },
+      {
+        input = { { a = { 1, 2 } }, { a = { 3 } } },
+        output = { a = { 3 } },
+      },
+      {
+        input = { { b = { 1, 2 } }, { a = { 3 }, __merge = false } },
+        output = { a = { 3 } },
+      },
+      {
+        input = { { a = 1 }, { b = 2, __merge = false } },
+        output = { b = 2 },
+      },
+      {
+        input = { { a = { 1, 2 } }, { a = { 3, __merge = true } } },
+        output = { a = { 1, 2, 3 } },
+      },
+      {
+        input = { { a = { 1, 2, __merge = true } }, { a = { 3 } } },
+        output = { a = { 1, 2, 3 } },
+      },
+      {
+        input = { { a = { 1, 2, __merge = true } }, { a = { 3, __merge = false } } },
+        output = { a = { 3 } },
+      },
+    }
+
+    for _, test in ipairs(tests) do
+      assert.same(test.output, Util.merge(unpack(test.input)))
+    end
+  end)
 end)