fix(vim.region): handle multibyte inclusive selection properly (#26129)

3 files changed, 19 insertions, 9 deletions

diff --git a/runtime/doc/lua.txt b/runtime/doc/lua.txt
index 596b58d4ff..b155e646ab 100644
--- a/runtime/doc/lua.txt
+++ b/runtime/doc/lua.txt
@@ -1728,7 +1728,7 @@ vim.region({bufnr}, {pos1}, {pos2}, {regtype}, {inclusive})
       • {pos2}       integer[]|string End of region as a (line, column) tuple
                      or |getpos()|-compatible string
       • {regtype}    (string) |setreg()|-style selection type
-      • {inclusive}  (boolean) Controls whether `pos2` column is inclusive
+      • {inclusive}  (boolean) Controls whether the ending column is inclusive
                      (see also 'selection').
 
     Return: ~
diff --git a/runtime/lua/vim/_editor.lua b/runtime/lua/vim/_editor.lua
index 98a1ce79ed..12b632075d 100644
--- a/runtime/lua/vim/_editor.lua
+++ b/runtime/lua/vim/_editor.lua
@@ -492,7 +492,7 @@ end
 ---@param pos1 integer[]|string Start of region as a (line, column) tuple or |getpos()|-compatible string
 ---@param pos2 integer[]|string End of region as a (line, column) tuple or |getpos()|-compatible string
 ---@param regtype string \|setreg()|-style selection type
----@param inclusive boolean Controls whether `pos2` column is inclusive (see also 'selection').
+---@param inclusive boolean Controls whether the ending column is inclusive (see also 'selection').
 ---@return table region Dict of the form `{linenr = {startcol,endcol}}`. `endcol` is exclusive, and
 ---whole lines are returned as `{startcol,endcol} = {0,-1}`.
 function vim.region(bufnr, pos1, pos2, regtype, inclusive)
@@ -502,11 +502,11 @@ function vim.region(bufnr, pos1, pos2, regtype, inclusive)
 
   if type(pos1) == 'string' then
     local pos = vim.fn.getpos(pos1)
-    pos1 = { pos[2] - 1, pos[3] - 1 + pos[4] }
+    pos1 = { pos[2] - 1, pos[3] - 1 }
   end
   if type(pos2) == 'string' then
     local pos = vim.fn.getpos(pos2)
-    pos2 = { pos[2] - 1, pos[3] - 1 + pos[4] }
+    pos2 = { pos[2] - 1, pos[3] - 1 }
   end
 
   if pos1[1] > pos2[1] or (pos1[1] == pos2[1] and pos1[2] > pos2[2]) then
@@ -525,9 +525,8 @@ function vim.region(bufnr, pos1, pos2, regtype, inclusive)
 
   -- in case of block selection, columns need to be adjusted for non-ASCII characters
   -- TODO: handle double-width characters
-  local bufline
   if regtype:byte() == 22 then
-    bufline = vim.api.nvim_buf_get_lines(bufnr, pos1[1], pos1[1] + 1, true)[1]
+    local bufline = vim.api.nvim_buf_get_lines(bufnr, pos1[1], pos1[1] + 1, true)[1]
     pos1[2] = vim.str_utfindex(bufline, pos1[2])
   end
 
@@ -538,7 +537,7 @@ function vim.region(bufnr, pos1, pos2, regtype, inclusive)
       c1 = pos1[2]
       c2 = c1 + regtype:sub(2)
       -- and adjust for non-ASCII characters
-      bufline = vim.api.nvim_buf_get_lines(bufnr, l, l + 1, true)[1]
+      local bufline = vim.api.nvim_buf_get_lines(bufnr, l, l + 1, true)[1]
       local utflen = vim.str_utfindex(bufline, #bufline)
       if c1 <= utflen then
         c1 = vim.str_byteindex(bufline, c1)
@@ -555,7 +554,11 @@ function vim.region(bufnr, pos1, pos2, regtype, inclusive)
       c2 = -1
     else
       c1 = (l == pos1[1]) and pos1[2] or 0
-      c2 = (l == pos2[1]) and (pos2[2] + (inclusive and 1 or 0)) or -1
+      if inclusive and l == pos2[1] then
+        local bufline = vim.api.nvim_buf_get_lines(bufnr, pos2[1], pos2[1] + 1, true)[1]
+        pos2[2] = vim.fn.byteidx(bufline, vim.fn.charidx(bufline, pos2[2]) + 1)
+      end
+      c2 = (l == pos2[1]) and pos2[2] or -1
     end
     table.insert(region, l, { c1, c2 })
   end
diff --git a/test/functional/lua/vim_spec.lua b/test/functional/lua/vim_spec.lua
index a8a72f20c9..1533a1823f 100644
--- a/test/functional/lua/vim_spec.lua
+++ b/test/functional/lua/vim_spec.lua
@@ -2395,7 +2395,14 @@ describe('lua stdlib', function()
       text tαxt txtα tex
       text tαxt tαxt
       ]]))
-      eq({5,15}, exec_lua[[ return vim.region(0,{1,5},{1,14},'v',true)[1] ]])
+      eq({5,13}, exec_lua[[ return vim.region(0,{0,5},{0,13},'v',false)[0] ]])
+      eq({5,15}, exec_lua[[ return vim.region(0,{0,5},{0,13},'v',true)[0] ]])
+      eq({5,15}, exec_lua[[ return vim.region(0,{0,5},{0,14},'v',true)[0] ]])
+      eq({5,15}, exec_lua[[ return vim.region(0,{0,5},{0,15},'v',false)[0] ]])
+      eq({5,17}, exec_lua[[ return vim.region(0,{0,5},{0,15},'v',true)[0] ]])
+      eq({5,17}, exec_lua[[ return vim.region(0,{0,5},{0,16},'v',true)[0] ]])
+      eq({5,17}, exec_lua[[ return vim.region(0,{0,5},{0,17},'v',false)[0] ]])
+      eq({5,18}, exec_lua[[ return vim.region(0,{0,5},{0,17},'v',true)[0] ]])
     end)
     it('blockwise', function()
       insert([[αα]])