From 74fd3611f291a2506c5534109689bb7b028f0566 Mon Sep 17 00:00:00 2001
From: Folke Lemaitre <folke.lemaitre@gmail.com>
Date: Thu, 6 Jun 2024 23:23:49 +0200
Subject: [PATCH] feat(util): opts merging now supports lists extending by
 tagging a table with __extend = true. Use with care

---
 lua/lazy/core/util.lua   | 14 +++++++++++++-
 tests/core/util_spec.lua | 12 ++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/lua/lazy/core/util.lua b/lua/lazy/core/util.lua
index e51e670..e76f0c4 100644
--- a/lua/lazy/core/util.lua
+++ b/lua/lazy/core/util.lua
@@ -387,6 +387,10 @@ 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 v.__extend
+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
@@ -402,7 +406,15 @@ function M.merge(...)
   end
   for i = 2, select("#", ...) do
     local value = select(i, ...)
-    if can_merge(ret) and can_merge(value) then
+    local are_t = type(ret) == "table" and type(value) == "table"
+    if are_t and (can_extend(ret) or can_extend(value)) then
+      for k, v in pairs(value) do
+        if k ~= "__extend" then
+          table.insert(ret, v)
+        end
+      end
+      ret.__extend = true
+    elseif are_t and can_merge(ret) and can_merge(value) then
       for k, v in pairs(value) do
         ret[k] = M.merge(ret[k], v)
       end
diff --git a/tests/core/util_spec.lua b/tests/core/util_spec.lua
index 643304d..f76f185 100644
--- a/tests/core/util_spec.lua
+++ b/tests/core/util_spec.lua
@@ -134,6 +134,18 @@ describe("util", function()
         input = { { a = 1 }, { b = 2, a = vim.NIL } },
         output = { b = 2 },
       },
+      {
+        input = { { 1, 2, __extend = true }, { 3, 4 } },
+        output = { 1, 2, 3, 4, __extend = true },
+      },
+      {
+        input = { { 1, 2, __extend = true }, { __extend = true, 3, 4 } },
+        output = { 1, 2, 3, 4, __extend = true },
+      },
+      {
+        input = { { 1, 2 }, { 3, 4, __extend = true } },
+        output = { 1, 2, 3, 4, __extend = true },
+      },
     }
 
     for _, test in ipairs(tests) do