fix(api): ignore 'autochdir' when renaming other buf (#28376)

Problem:  Renaming non-current buffer changes working directory when
          'autochdir' is set.
Solution: Temporarily disable 'autochdir'.  Add more tests for the
          win_set_buf change.

src/nvim/api/buffer.c

@@ -39,6 +39,7 @@
 #include "nvim/memory_defs.h"
 #include "nvim/move.h"
 #include "nvim/ops.h"
+#include "nvim/option_vars.h"
 #include "nvim/pos_defs.h"
 #include "nvim/state_defs.h"
 #include "nvim/types_defs.h"
@@ -984,12 +985,23 @@ void nvim_buf_set_name(Buffer buffer, String name, Error *err)
 
   try_start();
 
+  const bool is_curbuf = buf == curbuf;
+  const int save_acd = p_acd;
+  if (!is_curbuf) {
+    // Temporarily disable 'autochdir' when setting file name for another buffer.
+    p_acd = false;
+  }
+
   // Using aucmd_*: autocommands will be executed by rename_buffer
   aco_save_T aco;
   aucmd_prepbuf(&aco, buf);
   int ren_ret = rename_buffer(name.data);
   aucmd_restbuf(&aco);
 
+  if (!is_curbuf) {
+    p_acd = save_acd;
+  }
+
   if (try_end(err)) {
     return;
   }

src/nvim/autocmd.c

@@ -1340,7 +1340,7 @@ void aucmd_prepbuf(aco_save_T *aco, buf_T *buf)
       win_config_float(auc_win, auc_win->w_config);
     }
     // Prevent chdir() call in win_enter_ext(), through do_autochdir()
-    int save_acd = p_acd;
+    const int save_acd = p_acd;
     p_acd = false;
     // no redrawing and don't set the window title
     RedrawingDisabled++;

src/nvim/window.c

@@ -752,15 +752,20 @@ void win_set_buf(win_T *win, buf_T *buf, Error *err)
     goto cleanup;
   }
 
-  // temporarily disable 'autochdir' when using win_set_buf
-  // on non-current window
-  int save_acd = p_acd;
+  try_start();
+
+  const int save_acd = p_acd;
   if (!switchwin.sw_same_win) {
+    // Temporarily disable 'autochdir' when setting buffer in another window.
     p_acd = false;
   }
-  try_start();
+
   int result = do_buffer(DOBUF_GOTO, DOBUF_FIRST, FORWARD, buf->b_fnum, 0);
-  p_acd = save_acd;
+
+  if (!switchwin.sw_same_win) {
+    p_acd = save_acd;
+  }
+
   if (!try_end(err) && result == FAIL) {
     api_set_error(err,
                   kErrorTypeException,

test/functional/api/buffer_spec.lua

@@ -2048,6 +2048,37 @@ describe('api/buf', function()
       eq(1, fn.filereadable(new_name))
       os.remove(new_name)
     end)
+
+    describe("with 'autochdir'", function()
+      local topdir
+      local oldbuf
+      local newbuf
+
+      before_each(function()
+        command('set shellslash')
+        topdir = fn.getcwd()
+        t.mkdir(topdir .. '/Xacd')
+
+        oldbuf = api.nvim_get_current_buf()
+        command('vnew')
+        newbuf = api.nvim_get_current_buf()
+        command('set autochdir')
+      end)
+
+      after_each(function()
+        t.rmdir(topdir .. '/Xacd')
+      end)
+
+      it('does not change cwd with non-current buffer', function()
+        api.nvim_buf_set_name(oldbuf, topdir .. '/Xacd/foo.txt')
+        eq(topdir, fn.getcwd())
+      end)
+
+      it('changes cwd with current buffer', function()
+        api.nvim_buf_set_name(newbuf, topdir .. '/Xacd/foo.txt')
+        eq(topdir .. '/Xacd', fn.getcwd())
+      end)
+    end)
   end)
 
   describe('nvim_buf_is_loaded', function()

test/functional/api/window_spec.lua

@@ -111,6 +111,44 @@ describe('API/win', function()
       api.nvim_win_set_buf(new_win, next_buf)
       eq(next_buf, api.nvim_win_get_buf(new_win))
     end)
+
+    describe("with 'autochdir'", function()
+      local topdir
+      local otherbuf
+      local oldwin
+      local newwin
+
+      before_each(function()
+        command('set shellslash')
+        topdir = fn.getcwd()
+        t.mkdir(topdir .. '/Xacd')
+        t.mkdir(topdir .. '/Xacd/foo')
+        otherbuf = api.nvim_create_buf(false, true)
+        api.nvim_buf_set_name(otherbuf, topdir .. '/Xacd/baz.txt')
+
+        command('set autochdir')
+        command('edit Xacd/foo/bar.txt')
+        eq(topdir .. '/Xacd/foo', fn.getcwd())
+
+        oldwin = api.nvim_get_current_win()
+        command('vsplit')
+        newwin = api.nvim_get_current_win()
+      end)
+
+      after_each(function()
+        t.rmdir(topdir .. '/Xacd')
+      end)
+
+      it('does not change cwd with non-current window', function()
+        api.nvim_win_set_buf(oldwin, otherbuf)
+        eq(topdir .. '/Xacd/foo', fn.getcwd())
+      end)
+
+      it('changes cwd with current window', function()
+        api.nvim_win_set_buf(newwin, otherbuf)
+        eq(topdir .. '/Xacd', fn.getcwd())
+      end)
+    end)
   end)
 
   describe('{get,set}_cursor', function()
@@ -1749,29 +1787,44 @@ describe('API/win', function()
       )
     end)
 
-    it('do not change dir when enter is false', function()
-      local expected = fn.getcwd() .. '/foo'
-      t.mkdir('foo')
-      exec_lua [[
-        vim.opt.autochdir = true
-        local buf = vim.api.nvim_create_buf(false, true)
-        vim.api.nvim_buf_set_name(buf, 'Foo')
-        vim.api.nvim_create_autocmd('CmdlineEnter', {
-          callback = function()
-            local winid = vim.api.nvim_open_win(buf, false, {
-              relative = 'editor',
-              height = 1,
-              width = 1,
-              row = 1,
-              col = 1,
-            })
-            vim.api.nvim_win_close(winid, true)
-          end,
-        })
-      ]]
-      t.feed(':edit foo/bar.txt<CR>')
-      eq(t.is_os('win') and expected:gsub('/', '\\') or expected, fn.getcwd())
-      t.rmdir('foo')
+    describe("with 'autochdir'", function()
+      local topdir
+      local otherbuf
+
+      before_each(function()
+        command('set shellslash')
+        topdir = fn.getcwd()
+        t.mkdir(topdir .. '/Xacd')
+        t.mkdir(topdir .. '/Xacd/foo')
+        otherbuf = api.nvim_create_buf(false, true)
+        api.nvim_buf_set_name(otherbuf, topdir .. '/Xacd/baz.txt')
+
+        command('set autochdir')
+        command('edit Xacd/foo/bar.txt')
+        eq(topdir .. '/Xacd/foo', fn.getcwd())
+      end)
+
+      after_each(function()
+        t.rmdir(topdir .. '/Xacd')
+      end)
+
+      it('does not change cwd with enter=false #15280', function()
+        api.nvim_open_win(
+          otherbuf,
+          false,
+          { relative = 'editor', height = 5, width = 5, row = 5, col = 5 }
+        )
+        eq(topdir .. '/Xacd/foo', fn.getcwd())
+      end)
+
+      it('changes cwd with enter=true', function()
+        api.nvim_open_win(
+          otherbuf,
+          true,
+          { relative = 'editor', height = 5, width = 5, row = 5, col = 5 }
+        )
+        eq(topdir .. '/Xacd', fn.getcwd())
+      end)
     end)
   end)