feat(lua): allow vim.wo to be double indexed (#20288)

* feat(lua): allow vim.wo to be double indexed

Problem: `vim.wo` does not implement `setlocal`
Solution: Allow `vim.wo` to be double indexed

Co-authored-by: Christian Clason <c.clason@uni-graz.at>

3 files changed, 16 insertions, 9 deletions

diff --git a/runtime/doc/lua-guide.txt b/runtime/doc/lua-guide.txt
index b138de85c9..28c9ace23b 100644
--- a/runtime/doc/lua-guide.txt
+++ b/runtime/doc/lua-guide.txt
@@ -363,7 +363,7 @@ and `:let &listchars='space:_,tab:>~'`:
 • |vim.o|:  behaves like |:set|
 • |vim.go|: behaves like |:setglobal|
 • |vim.bo|: for buffer-scoped options
-• |vim.wo|: for window-scoped options
+• |vim.wo|: for window-scoped options (can be double indexed)
 
 For example:
 >lua
@@ -386,6 +386,9 @@ window is used:
 >lua
     vim.bo[4].expandtab = true -- sets expandtab to true in buffer 4
     vim.wo.number = true       -- sets number to true in current window
+    vim.wo[0].number = true    -- same as above 
+    vim.wo[0][0].number = true -- sets number to true in current buffer
+                               -- in current window only 
     print(vim.wo[0].number)    --> true
 <
 ------------------------------------------------------------------------------
diff --git a/runtime/doc/lua.txt b/runtime/doc/lua.txt
index ca4adbce9c..63523c32d5 100644
--- a/runtime/doc/lua.txt
+++ b/runtime/doc/lua.txt
@@ -1175,20 +1175,21 @@ vim.bo[{bufnr}]                                                                *
         print(vim.bo.comments)
         print(vim.bo.baz)                 -- error: invalid key
 <
-vim.wo[{winid}]                                                                *vim.wo*
-    Get or set window-scoped |options| for the window with handle {winid}.
-    Like `:set`. If [{winid}] is omitted then the current window is used.
-    Invalid {winid} or key is an error.
+vim.wo[{winid}][{bufnr}]                                                       *vim.wo*
+    Get or set window-scoped |options| for the window with handle {winid} and
+    buffer with number {bufnr}. Like `:setlocal` if {bufnr} is provided, like
+    `:set` otherwise. If [{winid}] is omitted then the current window is
+    used. Invalid {winid}, {bufnr} or key is an error.
+
+    Note: only {bufnr} with value `0` (the current buffer in the window) is
+    supported.
 
-    Note: this does not access |local-options| (`:setlocal`) instead use: >lua
-        nvim_get_option_value(OPTION, { scope = 'local', win = winid })
-        nvim_set_option_value(OPTION, VALUE, { scope = 'local', win = winid }
-<
     Example: >lua
         local winid = vim.api.nvim_get_current_win()
         vim.wo[winid].number = true    -- same as vim.wo.number = true
         print(vim.wo.foldmarker)
         print(vim.wo.quux)             -- error: invalid key
+        vim.wo[winid][0].spell = false -- like ':setlocal nospell'
 <
 
 
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index 24e9dc917b..ac0a57e4d3 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -110,6 +110,9 @@ The following new APIs and features were added.
 • |vim.ui.open()| opens URIs using the system default handler (macOS `open`,
   Windows `explorer`, Linux `xdg-open`, etc.)
 
+• |vim.wo| can now be double indexed for |:setlocal| behaviour. Currently only
+  `0` for the buffer index is currently supported.
+
 ==============================================================================
 CHANGED FEATURES                                                 *news-changed*