From b8b21015400656114cb689d399526a7a98ef5526 Mon Sep 17 00:00:00 2001
From: zeertzjq <zeertzjq@outlook.com>
Date: Sat, 10 Dec 2022 19:23:24 +0800
Subject: [PATCH] fix(api): set correct curbuf when temporarily changing curwin

(cherry picked from commit 44f22adb22032a176199bc75316e307378684ade)
---
 src/nvim/api/window.c               |  4 ++++
 test/functional/api/window_spec.lua | 33 +++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/src/nvim/api/window.c b/src/nvim/api/window.c
index 08dcc113da..eb089fbc05 100644
--- a/src/nvim/api/window.c
+++ b/src/nvim/api/window.c
@@ -162,9 +162,11 @@ void nvim_win_set_height(Window window, Integer height, Error *err)
 
   win_T *savewin = curwin;
   curwin = win;
+  curbuf = curwin->w_buffer;
   try_start();
   win_setheight((int)height);
   curwin = savewin;
+  curbuf = curwin->w_buffer;
   try_end(err);
 }
 
@@ -207,9 +209,11 @@ void nvim_win_set_width(Window window, Integer width, Error *err)
 
   win_T *savewin = curwin;
   curwin = win;
+  curbuf = curwin->w_buffer;
   try_start();
   win_setwidth((int)width);
   curwin = savewin;
+  curbuf = curwin->w_buffer;
   try_end(err);
 }
 
diff --git a/test/functional/api/window_spec.lua b/test/functional/api/window_spec.lua
index 901d24327c..362aed4838 100644
--- a/test/functional/api/window_spec.lua
+++ b/test/functional/api/window_spec.lua
@@ -7,6 +7,7 @@ local clear, nvim, curbuf, curbuf_contents, window, curwin, eq, neq,
   helpers.tabpage
 local poke_eventloop = helpers.poke_eventloop
 local curwinmeths = helpers.curwinmeths
+local exec = helpers.exec
 local funcs = helpers.funcs
 local request = helpers.request
 local NIL = helpers.NIL
@@ -201,6 +202,22 @@ describe('API/win', function()
       window('set_height', nvim('list_wins')[2], 2)
       eq(2, window('get_height', nvim('list_wins')[2]))
     end)
+
+    it('do not cause ml_get errors with foldmethod=expr #19989', function()
+      insert([[
+        aaaaa
+        bbbbb
+        ccccc]])
+      command('set foldmethod=expr')
+      exec([[
+        new
+        let w = nvim_get_current_win()
+        wincmd w
+        call nvim_win_set_height(w, 5)
+      ]])
+      feed('l')
+      eq('', meths.get_vvar('errmsg'))
+    end)
   end)
 
   describe('{get,set}_width', function()
@@ -215,6 +232,22 @@ describe('API/win', function()
       window('set_width', nvim('list_wins')[2], 2)
       eq(2, window('get_width', nvim('list_wins')[2]))
     end)
+
+    it('do not cause ml_get errors with foldmethod=expr #19989', function()
+      insert([[
+        aaaaa
+        bbbbb
+        ccccc]])
+      command('set foldmethod=expr')
+      exec([[
+        vnew
+        let w = nvim_get_current_win()
+        wincmd w
+        call nvim_win_set_width(w, 5)
+      ]])
+      feed('l')
+      eq('', meths.get_vvar('errmsg'))
+    end)
   end)
 
   describe('{get,set,del}_var', function()