fix(api): use correct buffer for "range" in nvim__redraw (#28614)

2 files changed, 17 insertions, 14 deletions

diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index d8ebc4b94f..f5b7c8abdd 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -2415,10 +2415,11 @@ void nvim__redraw(Dict(redraw) *opts, Error *err)
     });
     linenr_T first = (linenr_T)kv_A(opts->range, 0).data.integer + 1;
     linenr_T last = (linenr_T)kv_A(opts->range, 1).data.integer;
-    if (last < 0) {
-      last = buf->b_ml.ml_line_count;
+    buf_T *rbuf = win ? win->w_buffer : (buf ? buf : curbuf);
+    if (last == -1) {
+      last = rbuf->b_ml.ml_line_count;
     }
-    redraw_buf_range_later(win ? win->w_buffer : (buf ? buf : curbuf), first, last);
+    redraw_buf_range_later(rbuf, first, last);
   }
 
   if (opts->cursor) {
diff --git a/test/functional/api/vim_spec.lua b/test/functional/api/vim_spec.lua
index fbb6d42633..c56c8263d6 100644
--- a/test/functional/api/vim_spec.lua
+++ b/test/functional/api/vim_spec.lua
@@ -5195,28 +5195,27 @@ describe('API', function()
     })
     -- valid = true does not draw any lines on its own
     exec_lua([[
-      lines = 0
+      _G.lines = 0
       ns = vim.api.nvim_create_namespace('')
-      on_win = function()
-        if do_win then
-          vim.api.nvim_buf_set_extmark(0, ns, 0, 0, { hl_group = 'IncSearch', end_col = 6 })
-        end
-      end
       vim.api.nvim_set_decoration_provider(ns, {
-        on_win = on_win,
+        on_win = function()
+          if _G.do_win then
+            vim.api.nvim_buf_set_extmark(0, ns, 0, 0, { hl_group = 'IncSearch', end_col = 6 })
+          end
+        end,
         on_line = function()
-          lines = lines + 1
+          _G.lines = _G.lines + 1
         end,
       })
     ]])
     local lines = exec_lua('return lines')
     api.nvim__redraw({ buf = 0, valid = true, flush = true })
-    eq(lines, exec_lua('return lines'))
+    eq(lines, exec_lua('return _G.lines'))
     -- valid = false does
     api.nvim__redraw({ buf = 0, valid = false, flush = true })
-    neq(lines, exec_lua('return lines'))
+    neq(lines, exec_lua('return _G.lines'))
     -- valid = true does redraw lines if affected by on_win callback
-    exec_lua('do_win = true')
+    exec_lua('_G.do_win = true')
     api.nvim__redraw({ buf = 0, valid = true, flush = true })
     screen:expect({
       grid = [[
@@ -5227,5 +5226,8 @@ describe('API', function()
         13                                                          |
       ]],
     })
+    -- takes buffer line count from correct buffer with "win" and {0, -1} "range"
+    api.nvim__redraw({ win = 0, range = { 0, -1 } })
+    n.assert_alive()
   end)
 end)