feat: ":wall ++p" creates parent dirs for each buf #36121

`:wall ++p` will create parent directories if they do not exist, for
each modified buffer

runtime/doc/editing.txt

@@ -996,11 +996,13 @@ slower (but safer).
 WRITING WITH MULTIPLE BUFFERS				*buffer-write*
 
 							*:wa* *:wall*
-:wa[ll]			Write all changed buffers.  Buffers without a file
+:wa[ll]	[++opt]		Write all changed buffers.  Buffers without a file
 			name cause an error message.  Buffers which are
 			readonly are not written.
+			For ++opt see |++opt|, but only ++p is effective, and
+			applies to each written file.
 
-:wa[ll]!		Write all changed buffers, even the ones that are
+:wa[ll]! [++opt]	Write all changed buffers, even the ones that are
 			readonly.  Buffers without a file name are not
 			written and cause an error message.
 

runtime/doc/news.txt

@@ -197,6 +197,8 @@ EDITOR
 • |gx| in help buffers opens the online documentation for the tag under the
   cursor.
 • |:Undotree| for visually navigating the |undo-tree|
+• |:wall| permits a |++p| option for creating parent directories when writing
+  changed buffers.
 
 EVENTS
 

src/nvim/ex_cmds.c

@@ -1806,6 +1806,15 @@ static int check_writable(const char *fname)
 }
 #endif
 
+static int handle_mkdir_p_arg(exarg_T *eap, char *fname)
+{
+  if (eap->mkdir_p && os_file_mkdir(fname, 0755) < 0) {
+    return FAIL;
+  }
+
+  return OK;
+}
+
 /// Write current buffer to file "eap->arg".
 /// If "eap->append" is true, append to the file.
 ///
@@ -1943,11 +1952,9 @@ int do_write(exarg_T *eap)
       fname = curbuf->b_sfname;
     }
 
-    if (eap->mkdir_p) {
-      if (os_file_mkdir(fname, 0755) < 0) {
-        retval = FAIL;
-        goto theend;
-      }
+    if (handle_mkdir_p_arg(eap, fname) == FAIL) {
+      retval = FAIL;
+      goto theend;
     }
 
     int name_was_missing = curbuf->b_ffname == NULL;
@@ -2123,7 +2130,8 @@ void do_wqall(exarg_T *eap)
     } else {
       bufref_T bufref;
       set_bufref(&bufref, buf);
-      if (buf_write_all(buf, eap->forceit) == FAIL) {
+      if (handle_mkdir_p_arg(eap, buf->b_fname) == FAIL
+          || buf_write_all(buf, eap->forceit) == FAIL) {
         error++;
       }
       // An autocommand may have deleted the buffer.

src/nvim/ex_cmds.lua

@@ -3187,7 +3187,7 @@ M.cmds = {
   },
   {
     command = 'wall',
-    flags = bit.bor(BANG, TRLBAR, CMDWIN, LOCK_OK),
+    flags = bit.bor(BANG, TRLBAR, CMDWIN, LOCK_OK, ARGOPT),
     addr_type = 'ADDR_NONE',
     func = 'do_wqall',
   },

test/functional/ex_cmds/write_spec.lua

@@ -23,6 +23,9 @@ describe(':write', function()
     os.remove('test_fifo')
     os.remove('test/write/p_opt.txt')
     os.remove('test/write')
+    os.remove('test/write2/p_opt.txt')
+    os.remove('test/write2/p_opt2.txt')
+    os.remove('test/write2')
     os.remove('test')
     os.remove(fname)
     os.remove(fname_bak)
@@ -111,6 +114,21 @@ describe(':write', function()
     command('write ++p test/write/p_opt.txt')
     eq(1, eval("filereadable('test/write/p_opt.txt')"))
 
+    eq(0, eval("filereadable('test/write2/p_opt.txt')"))
+    eq(0, eval("filereadable('test/write2/p_opt2.txt')"))
+    eq(0, eval("filereadable('test/write3/p_opt3.txt')"))
+    command('file test/write2/p_opt.txt')
+    command('set modified')
+    command('sp test/write2/p_opt2.txt')
+    command('set modified')
+    command('sp test/write3/p_opt3.txt')
+    -- don't set p_opt3.txt modified - assert it isn't written
+    -- and that write3/ isn't created
+    command('wall ++p')
+    eq(1, eval("filereadable('test/write2/p_opt.txt')"))
+    eq(1, eval("filereadable('test/write2/p_opt2.txt')"))
+    eq(0, eval("filereadable('test/write3/p_opt3.txt')"))
+
     eq('Vim(write):E32: No file name', pcall_err(command, 'write ++p test_write/'))
     if not is_os('win') then
       eq(