feat(util): opts merging now supports lists extending by tagging a table with __extend = true. Use with care

Author: folke

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

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