lua: add tbl_deep_extend (#11969)

runtime/lua/vim/shared.lua

@@ -200,16 +200,7 @@ function vim.tbl_isempty(t)
   return next(t) == nil
 end
 
---- Merges two or more map-like tables.
+local function tbl_extend(behavior, deep_extend, ...)
----
---@see |extend()|
----
---@param behavior Decides what to do if a key is found in more than one map:
----      - "error": raise an error
----      - "keep":  use value from the leftmost map
----      - "force": use value from the rightmost map
---@param ... Two or more map-like tables.
-function vim.tbl_extend(behavior, ...)
   if (behavior ~= 'error' and behavior ~= 'keep' and behavior ~= 'force') then
     error('invalid "behavior": '..tostring(behavior))
   end
@@ -228,7 +219,9 @@ function vim.tbl_extend(behavior, ...)
     vim.validate{["after the second argument"] = {tbl,'t'}}
     if tbl then
       for k, v in pairs(tbl) do
-        if behavior ~= 'force' and ret[k] ~= nil then
+        if type(v) == 'table' and deep_extend and not vim.tbl_islist(v) then
+          ret[k] = tbl_extend(behavior, true, ret[k] or vim.empty_dict(), v)
+        elseif behavior ~= 'force' and ret[k] ~= nil then
           if behavior == 'error' then
             error('key found in more than one map: '..k)
           end  -- Else behavior is "keep".
@@ -241,6 +234,32 @@ function vim.tbl_extend(behavior, ...)
   return ret
 end
 
+--- Merges two or more map-like tables.
+---
+--@see |extend()|
+---
+--@param behavior Decides what to do if a key is found in more than one map:
+---      - "error": raise an error
+---      - "keep":  use value from the leftmost map
+---      - "force": use value from the rightmost map
+--@param ... Two or more map-like tables.
+function vim.tbl_extend(behavior, ...)
+  return tbl_extend(behavior, false, ...)
+end
+
+--- Merges recursively two or more map-like tables.
+---
+--@see |tbl_extend()|
+---
+--@param behavior Decides what to do if a key is found in more than one map:
+---      - "error": raise an error
+---      - "keep":  use value from the leftmost map
+---      - "force": use value from the rightmost map
+--@param ... Two or more map-like tables.
+function vim.tbl_deep_extend(behavior, ...)
+  return tbl_extend(behavior, true, ...)
+end
+
 --- Deep compare values for equality
 function vim.deep_equal(a, b)
   if a == b then return true end

test/functional/lua/vim_spec.lua

@@ -478,6 +478,17 @@ describe('lua stdlib', function()
       return vim.tbl_islist(c) and vim.tbl_count(c) == 0
     ]]))
 
+    ok(exec_lua([[
+      local a = {x = {a = 1, b = 2}}
+      local b = {x = {a = 2, c = {y = 3}}}
+      local c = vim.tbl_extend("keep", a, b)
+
+      local count = 0
+      for _ in pairs(c) do count = count + 1 end
+
+      return c.x.a == 1 and c.x.b == 2 and c.x.c == nil and count == 1
+    ]]))
+
     eq('Error executing lua: .../shared.lua: invalid "behavior": nil',
       pcall_err(exec_lua, [[
         return vim.tbl_extend()
@@ -497,6 +508,94 @@ describe('lua stdlib', function()
     )
   end)
 
+  it('vim.tbl_deep_extend', function()
+    ok(exec_lua([[
+      local a = {x = {a = 1, b = 2}}
+      local b = {x = {a = 2, c = {y = 3}}}
+      local c = vim.tbl_deep_extend("keep", a, b)
+
+      local count = 0
+      for _ in pairs(c) do count = count + 1 end
+
+      return c.x.a == 1 and c.x.b == 2 and c.x.c.y == 3 and count == 1
+    ]]))
+
+    ok(exec_lua([[
+      local a = {x = {a = 1, b = 2}}
+      local b = {x = {a = 2, c = {y = 3}}}
+      local c = vim.tbl_deep_extend("force", a, b)
+
+      local count = 0
+      for _ in pairs(c) do count = count + 1 end
+
+      return c.x.a == 2 and c.x.b == 2 and c.x.c.y == 3 and count == 1
+    ]]))
+
+    ok(exec_lua([[
+      local a = {x = {a = 1, b = 2}}
+      local b = {x = {a = 2, c = {y = 3}}}
+      local c = {x = {c = 4, d = {y = 4}}}
+      local d = vim.tbl_deep_extend("keep", a, b, c)
+
+      local count = 0
+      for _ in pairs(c) do count = count + 1 end
+
+      return d.x.a == 1 and d.x.b == 2 and d.x.c.y == 3 and d.x.d.y == 4 and count == 1
+    ]]))
+
+    ok(exec_lua([[
+      local a = {x = {a = 1, b = 2}}
+      local b = {x = {a = 2, c = {y = 3}}}
+      local c = {x = {c = 4, d = {y = 4}}}
+      local d = vim.tbl_deep_extend("force", a, b, c)
+
+      local count = 0
+      for _ in pairs(c) do count = count + 1 end
+
+      return d.x.a == 2 and d.x.b == 2 and d.x.c == 4 and d.x.d.y == 4 and count == 1
+    ]]))
+
+    ok(exec_lua([[
+      local a = vim.empty_dict()
+      local b = {}
+      local c = vim.tbl_deep_extend("keep", a, b)
+
+      local count = 0
+      for _ in pairs(c) do count = count + 1 end
+
+      return not vim.tbl_islist(c) and count == 0
+    ]]))
+
+    ok(exec_lua([[
+      local a = {}
+      local b = vim.empty_dict()
+      local c = vim.tbl_deep_extend("keep", a, b)
+
+      local count = 0
+      for _ in pairs(c) do count = count + 1 end
+
+      return vim.tbl_islist(c) and count == 0
+    ]]))
+
+    eq('Error executing lua: .../shared.lua: invalid "behavior": nil',
+      pcall_err(exec_lua, [[
+        return vim.tbl_deep_extend()
+      ]])
+    )
+
+    eq('Error executing lua: .../shared.lua: wrong number of arguments (given 1, expected at least 3)',
+      pcall_err(exec_lua, [[
+        return vim.tbl_deep_extend("keep")
+      ]])
+    )
+
+    eq('Error executing lua: .../shared.lua: wrong number of arguments (given 2, expected at least 3)',
+      pcall_err(exec_lua, [[
+        return vim.tbl_deep_extend("keep", {})
+      ]])
+    )
+  end)
+
   it('vim.tbl_count', function()
     eq(0, exec_lua [[ return vim.tbl_count({}) ]])
     eq(0, exec_lua [[ return vim.tbl_count(vim.empty_dict()) ]])