api: add nvim_win_close() to close window by id

src/nvim/api/window.c

@@ -9,6 +9,7 @@
 #include "nvim/api/window.h"
 #include "nvim/api/private/defs.h"
 #include "nvim/api/private/helpers.h"
+#include "nvim/ex_docmd.h"
 #include "nvim/vim.h"
 #include "nvim/buffer.h"
 #include "nvim/cursor.h"
@@ -470,3 +471,29 @@ void nvim_win_config(Window window, Integer width, Integer height,
     win->w_pos_changed = true;
   }
 }
+
+/// Close a window.
+///
+/// This is equivalent to |:close| with count except that it takes a window id.
+///
+/// @param window   Window handle
+/// @param force    Behave like `:close!` The last window of a buffer with
+///                 unwritten changes can be closed. The buffer will become
+///                 hidden, even if 'hidden' is not set.
+///
+/// @param[out] err Error details, if any
+/// @return Window number
+void nvim_win_close(Window window, Boolean force, Error *err)
+  FUNC_API_SINCE(6)
+{
+  win_T *win = find_window_by_handle(window, err);
+  if (!win) {
+    return;
+  }
+  tabpage_T *tabpage = win_find_tabpage(win);
+
+  TryState tstate;
+  try_enter(&tstate);
+  ex_win_close(force, win, tabpage == curtab ? NULL : tabpage);
+  vim_ignored = try_leave(&tstate, err);
+}

src/nvim/ex_docmd.c

@@ -6170,7 +6170,7 @@ static void ex_pclose(exarg_T *eap)
  * Close window "win" and take care of handling closing the last window for a
  * modified buffer.
  */
-static void
+void
 ex_win_close(
     int forceit,
     win_T *win,

test/functional/api/window_spec.lua

@@ -286,4 +286,41 @@ describe('API/win', function()
       ok(not window('is_valid', win))
     end)
   end)
+
+  describe('close', function()
+    it('can close current window', function()
+      local oldwin = meths.get_current_win()
+      command('split')
+      local newwin = meths.get_current_win()
+      meths.win_close(newwin,false)
+      eq({oldwin}, meths.list_wins())
+    end)
+
+    it('can close noncurrent window', function()
+      local oldwin = meths.get_current_win()
+      command('split')
+      local newwin = meths.get_current_win()
+      meths.win_close(oldwin,false)
+      eq({newwin}, meths.list_wins())
+    end)
+
+    it('handles changed buffer', function()
+      local oldwin = meths.get_current_win()
+      insert('text')
+      command('new')
+      local newwin = meths.get_current_win()
+      eq({false,"Vim:E37: No write since last change (add ! to override)"},
+         meth_pcall(meths.win_close, oldwin,false))
+      eq({newwin,oldwin}, meths.list_wins())
+    end)
+
+    it('handles changed buffer with force', function()
+      local oldwin = meths.get_current_win()
+      insert('text')
+      command('new')
+      local newwin = meths.get_current_win()
+      meths.win_close(oldwin,true)
+      eq({newwin}, meths.list_wins())
+    end)
+  end)
 end)

test/functional/ui/float_spec.lua

@@ -118,6 +118,37 @@ describe('floating windows', function()
                                                   |
         ]])
       end
+
+      meths.win_close(win, false)
+      if multigrid then
+        screen:expect([[
+        ## grid 1
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+                                                  |
+        ## grid 2
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+        ]])
+      else
+        screen:expect([[
+          ^                                        |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+                                                  |
+        ]])
+      end
     end)
 
     it('API has proper error messages', function()