lua: Add buffer, window and tab accessors (#12268)

* Add buffer, window and tab accessors

* Fix deletion and add tests

src/nvim/lua/vim.lua

@@ -332,9 +332,26 @@ do
       return pcall_ret(pcall(fn, ...))
     end
   end
+
+  vim.b = make_meta_accessor(
+    nil_wrap(function(v) return a.nvim_buf_get_var(0, v) end),
+    function(v, k) return a.nvim_buf_set_var(0, v, k) end,
+    function(v) return a.nvim_buf_del_var(0, v) end
+  )
+  vim.w = make_meta_accessor(
+    nil_wrap(function(v) return a.nvim_win_get_var(0, v) end),
+    function(v, k) return a.nvim_win_set_var(0, v, k) end,
+    function(v) return a.nvim_win_del_var(0, v) end
+  )
+  vim.t = make_meta_accessor(
+    nil_wrap(function(v) return a.nvim_tabpage_get_var(0, v) end),
+    function(v, k) return a.nvim_tabpage_set_var(0, v, k) end,
+    function(v) return a.nvim_tabpage_del_var(0, v) end
+  )
   vim.g = make_meta_accessor(nil_wrap(a.nvim_get_var), a.nvim_set_var, a.nvim_del_var)
   vim.v = make_meta_accessor(nil_wrap(a.nvim_get_vvar), a.nvim_set_vvar)
   vim.o = make_meta_accessor(a.nvim_get_option, a.nvim_set_option)
+
   local function getenv(k)
     local v = vim.fn.getenv(k)
     if v == vim.NIL then

test/functional/lua/vim_spec.lua

@@ -769,10 +769,96 @@ describe('lua stdlib', function()
     exec_lua [[
     vim.api.nvim_set_var("testing", "hi")
     vim.api.nvim_set_var("other", 123)
+    vim.api.nvim_set_var("to_delete", {hello="world"})
     ]]
+
     eq('hi', funcs.luaeval "vim.g.testing")
     eq(123, funcs.luaeval "vim.g.other")
     eq(NIL, funcs.luaeval "vim.g.nonexistant")
+
+    eq({hello="world"}, funcs.luaeval "vim.g.to_delete")
+    exec_lua [[
+    vim.g.to_delete = nil
+    ]]
+    eq(NIL, funcs.luaeval "vim.g.to_delete")
+  end)
+
+  it('vim.b', function()
+    exec_lua [[
+    vim.api.nvim_buf_set_var(0, "testing", "hi")
+    vim.api.nvim_buf_set_var(0, "other", 123)
+    vim.api.nvim_buf_set_var(0, "to_delete", {hello="world"})
+    ]]
+
+    eq('hi', funcs.luaeval "vim.b.testing")
+    eq(123, funcs.luaeval "vim.b.other")
+    eq(NIL, funcs.luaeval "vim.b.nonexistant")
+
+    eq({hello="world"}, funcs.luaeval "vim.b.to_delete")
+    exec_lua [[
+    vim.b.to_delete = nil
+    ]]
+    eq(NIL, funcs.luaeval "vim.b.to_delete")
+
+    exec_lua [[
+    vim.cmd "vnew"
+    ]]
+
+    eq(NIL, funcs.luaeval "vim.b.testing")
+    eq(NIL, funcs.luaeval "vim.b.other")
+    eq(NIL, funcs.luaeval "vim.b.nonexistant")
+  end)
+
+  it('vim.w', function()
+    exec_lua [[
+    vim.api.nvim_win_set_var(0, "testing", "hi")
+    vim.api.nvim_win_set_var(0, "other", 123)
+    vim.api.nvim_win_set_var(0, "to_delete", {hello="world"})
+    ]]
+
+    eq('hi', funcs.luaeval "vim.w.testing")
+    eq(123, funcs.luaeval "vim.w.other")
+    eq(NIL, funcs.luaeval "vim.w.nonexistant")
+
+    eq({hello="world"}, funcs.luaeval "vim.w.to_delete")
+    exec_lua [[
+    vim.w.to_delete = nil
+    ]]
+    eq(NIL, funcs.luaeval "vim.w.to_delete")
+
+    exec_lua [[
+    vim.cmd "vnew"
+    ]]
+
+    eq(NIL, funcs.luaeval "vim.w.testing")
+    eq(NIL, funcs.luaeval "vim.w.other")
+    eq(NIL, funcs.luaeval "vim.w.nonexistant")
+  end)
+
+  it('vim.t', function()
+    exec_lua [[
+    vim.api.nvim_tabpage_set_var(0, "testing", "hi")
+    vim.api.nvim_tabpage_set_var(0, "other", 123)
+    vim.api.nvim_tabpage_set_var(0, "to_delete", {hello="world"})
+    ]]
+
+    eq('hi', funcs.luaeval "vim.t.testing")
+    eq(123, funcs.luaeval "vim.t.other")
+    eq(NIL, funcs.luaeval "vim.t.nonexistant")
+
+    eq({hello="world"}, funcs.luaeval "vim.t.to_delete")
+    exec_lua [[
+    vim.t.to_delete = nil
+    ]]
+    eq(NIL, funcs.luaeval "vim.t.to_delete")
+
+    exec_lua [[
+    vim.cmd "tabnew"
+    ]]
+
+    eq(NIL, funcs.luaeval "vim.t.testing")
+    eq(NIL, funcs.luaeval "vim.t.other")
+    eq(NIL, funcs.luaeval "vim.t.nonexistant")
   end)
 
   it('vim.env', function()