6 files changed, 48 insertions, 46 deletions
diff --git a/runtime/lua/vim/diagnostic.lua b/runtime/lua/vim/diagnostic.lua
index a447463dff..897837a5ce 100644
--- a/runtime/lua/vim/diagnostic.lua
+++ b/runtime/lua/vim/diagnostic.lua
@@ -134,7 +134,7 @@ local function prefix_source(diagnostics)
       return d
     end
 
-    local t = vim.deepcopy(d)
+    local t = vim.deepcopy(d, true)
     t.message = string.format('%s: %s', d.source, d.message)
     return t
   end, diagnostics)
@@ -146,7 +146,7 @@ local function reformat_diagnostics(format, diagnostics)
     diagnostics = { diagnostics, 't' },
   })
 
-  local formatted = vim.deepcopy(diagnostics)
+  local formatted = vim.deepcopy(diagnostics, true)
   for _, diagnostic in ipairs(formatted) do
     diagnostic.message = format(diagnostic)
   end
@@ -373,7 +373,7 @@ local function get_diagnostics(bufnr, opts, clamp)
           or d.col < 0
           or d.end_col < 0
         then
-          d = vim.deepcopy(d)
+          d = vim.deepcopy(d, true)
           d.lnum = math.max(math.min(d.lnum, line_count), 0)
           d.end_lnum = math.max(math.min(d.end_lnum, line_count), 0)
           d.col = math.max(d.col, 0)
@@ -636,7 +636,7 @@ function M.config(opts, namespace)
 
   if not opts then
     -- Return current config
-    return vim.deepcopy(t)
+    return vim.deepcopy(t, true)
   end
 
   for k, v in pairs(opts) do
@@ -723,7 +723,7 @@ end
 ---
 ---@return table A list of active diagnostic namespaces |vim.diagnostic|.
 function M.get_namespaces()
-  return vim.deepcopy(all_namespaces)
+  return vim.deepcopy(all_namespaces, true)
 end
 
 ---@class Diagnostic
@@ -756,7 +756,7 @@ function M.get(bufnr, opts)
     opts = { opts, 't', true },
   })
 
-  return vim.deepcopy(get_diagnostics(bufnr, opts, false))
+  return vim.deepcopy(get_diagnostics(bufnr, opts, false), true)
 end
 
 --- Get current diagnostics count.
diff --git a/runtime/lua/vim/keymap.lua b/runtime/lua/vim/keymap.lua
index bdea95f9ab..8e4e123fe0 100644
--- a/runtime/lua/vim/keymap.lua
+++ b/runtime/lua/vim/keymap.lua
@@ -44,7 +44,7 @@ function keymap.set(mode, lhs, rhs, opts)
     opts = { opts, 't', true },
   })
 
-  opts = vim.deepcopy(opts or {})
+  opts = vim.deepcopy(opts or {}, true)
 
   ---@cast mode string[]
   mode = type(mode) == 'string' and { mode } or mode
diff --git a/runtime/lua/vim/lsp.lua b/runtime/lua/vim/lsp.lua
index 27c5f7ce7b..b2aa943359 100644
--- a/runtime/lua/vim/lsp.lua
+++ b/runtime/lua/vim/lsp.lua
@@ -1353,7 +1353,7 @@ function lsp.start_client(config)
   ---@param context? {bufnr: integer}
   ---@param handler? lsp.Handler only called if a server command
   function client._exec_cmd(command, context, handler)
-    context = vim.deepcopy(context or {}) --[[@as lsp.HandlerContext]]
+    context = vim.deepcopy(context or {}, true) --[[@as lsp.HandlerContext]]
     context.bufnr = context.bufnr or api.nvim_get_current_buf()
     context.client_id = client.id
     local cmdname = command.command
diff --git a/runtime/lua/vim/lsp/protocol.lua b/runtime/lua/vim/lsp/protocol.lua
index df12c36396..35eb0305d7 100644
--- a/runtime/lua/vim/lsp/protocol.lua
+++ b/runtime/lua/vim/lsp/protocol.lua
@@ -314,7 +314,7 @@ local constants = {
 }
 
 for k, v in pairs(constants) do
-  local tbl = vim.deepcopy(v)
+  local tbl = vim.deepcopy(v, true)
   vim.tbl_add_reverse_lookup(tbl)
   protocol[k] = tbl
 end
diff --git a/runtime/lua/vim/shared.lua b/runtime/lua/vim/shared.lua
index bbbc888727..87ab21a28f 100644
--- a/runtime/lua/vim/shared.lua
+++ b/runtime/lua/vim/shared.lua
@@ -9,43 +9,36 @@
 ---@diagnostic disable-next-line: lowercase-global
 vim = vim or {}
 
-local function _id(v)
-  return v
-end
+---@generic T
+---@param orig T
+---@param cache? table<any,any>
+---@return T
+local function deepcopy(orig, cache)
+  if orig == vim.NIL then
+    return vim.NIL
+  elseif type(orig) == 'userdata' or type(orig) == 'thread' then
+    error('Cannot deepcopy object of type ' .. type(orig))
+  elseif type(orig) ~= 'table' then
+    return orig
+  end
 
-local deepcopy
+  --- @cast orig table<any,any>
 
-local deepcopy_funcs = {
-  table = function(orig, cache)
-    if cache[orig] then
-      return cache[orig]
-    end
-    local copy = {}
+  if cache and cache[orig] then
+    return cache[orig]
+  end
 
+  local copy = {} --- @type table<any,any>
+
+  if cache then
     cache[orig] = copy
-    local mt = getmetatable(orig)
-    for k, v in pairs(orig) do
-      copy[deepcopy(k, cache)] = deepcopy(v, cache)
-    end
-    return setmetatable(copy, mt)
-  end,
-  number = _id,
-  string = _id,
-  ['nil'] = _id,
-  boolean = _id,
-  ['function'] = _id,
-}
-
-deepcopy = function(orig, _cache)
-  local f = deepcopy_funcs[type(orig)]
-  if f then
-    return f(orig, _cache or {})
-  else
-    if type(orig) == 'userdata' and orig == vim.NIL then
-      return vim.NIL
-    end
-    error('Cannot deepcopy object of type ' .. type(orig))
   end
+
+  for k, v in pairs(orig) do
+    copy[deepcopy(k, cache)] = deepcopy(v, cache)
+  end
+
+  return setmetatable(copy, getmetatable(orig))
 end
 
 --- Returns a deep copy of the given object. Non-table objects are copied as
@@ -54,11 +47,20 @@ end
 --- same functions as those in the input table. Userdata and threads are not
 --- copied and will throw an error.
 ---
+--- Note: `noref=true` is much more performant on tables with unique table
+--- fields, while `noref=false` is more performant on tables that reuse table
+--- fields.
+---
 ---@generic T: table
 ---@param orig T Table to copy
+---@param noref? boolean
+--- When `false` (default) a contained table is only copied once and all
+--- references point to this single copy. When `true` every occurrence of a
+--- table results in a new copy. This also means that a cyclic reference can
+--- cause `deepcopy()` to fail.
 ---@return T Table of copied keys and (nested) values.
-function vim.deepcopy(orig)
-  return deepcopy(orig)
+function vim.deepcopy(orig, noref)
+  return deepcopy(orig, not noref and {} or nil)
 end
 
 --- Gets an |iterator| that splits a string at each instance of a separator, in "lazy" fashion
diff --git a/runtime/lua/vim/version.lua b/runtime/lua/vim/version.lua
index 306eef90d3..0873402e29 100644
--- a/runtime/lua/vim/version.lua
+++ b/runtime/lua/vim/version.lua
@@ -158,7 +158,7 @@ end
 function M._version(version, strict) -- Adapted from https://github.com/folke/lazy.nvim
   if type(version) == 'table' then
     if version.major then
-      return setmetatable(vim.deepcopy(version), Version)
+      return setmetatable(vim.deepcopy(version, true), Version)
     end
     return setmetatable({
       major = version[1] or 0,
@@ -228,7 +228,7 @@ function VersionRange:has(version)
     version = M.parse(version)
   elseif getmetatable(version) ~= Version then
     -- Need metatable to compare versions.
-    version = setmetatable(vim.deepcopy(version), Version)
+    version = setmetatable(vim.deepcopy(version, true), Version)
   end
   if version then
     if version.prerelease ~= self.from.prerelease then
@@ -298,7 +298,7 @@ function M.range(spec) -- Adapted from https://github.com/folke/lazy.nvim
   local semver = M.parse(version)
   if semver then
     local from = semver
-    local to = vim.deepcopy(semver)
+    local to = vim.deepcopy(semver, true)
     if mods == '' or mods == '=' then
       to.patch = to.patch + 1
     elseif mods == '<' then