patch 8.2.4335: no autocommand event triggered before changing directory

Problem:    No autocommand event triggered before changing directory. (Ronnie
            Magatti)
Solution:   Add DirChangedPre. (closes #9721)

runtime/doc/autocmd.txt

@@ -326,6 +326,7 @@ Name			triggered by ~
 |FileChangedRO|		before making the first change to a read-only file
 
 |DiffUpdated|		after diffs have been updated
+|DirChangedPre|		before the working directory will change
 |DirChanged|		after the working directory has changed
 
 |ShellCmdPost|		after executing a shell command
@@ -738,6 +739,11 @@ DiffUpdated			After diffs have been updated.  Depending on
 				what kind of diff is being used (internal or
 				external) this can be triggered on every
 				change or when doing |:diffupdate|.
+							*DirChangedPre*
+DirChangedPre			The working directory is going to be changed,
+				as with ||DirChanged|.  The pattern is like
+				with |DirChanged|.  The new directory can be
+				found in v:event.directory.
 							*DirChanged*
 DirChanged			The working directory has changed in response
 				to the |:cd| or |:tcd| or |:lcd| commands, or

src/autocmd.c

@@ -119,6 +119,7 @@ static struct event_name
     {"CursorMovedI",	EVENT_CURSORMOVEDI},
     {"DiffUpdated",	EVENT_DIFFUPDATED},
     {"DirChanged",	EVENT_DIRCHANGED},
+    {"DirChangedPre",	EVENT_DIRCHANGEDPRE},
     {"EncodingChanged",	EVENT_ENCODINGCHANGED},
     {"ExitPre",		EVENT_EXITPRE},
     {"FileEncoding",	EVENT_ENCODINGCHANGED},

src/ex_docmd.c

@@ -7342,6 +7342,26 @@ post_chdir(cdscope_T scope)
     shorten_fnames(TRUE);
 }
 
+/*
+ * Trigger DirChangedPre for "acmd_fname" with directory "new_dir".
+ */
+    void
+trigger_DirChangedPre(char_u *acmd_fname, char_u *new_dir)
+{
+#ifdef FEAT_EVAL
+    dict_T	    *v_event;
+    save_v_event_T  save_v_event;
+
+    v_event = get_v_event(&save_v_event);
+    (void)dict_add_string(v_event, "directory", new_dir);
+    dict_set_items_ro(v_event);
+#endif
+    apply_autocmds(EVENT_DIRCHANGEDPRE, acmd_fname, new_dir, FALSE, curbuf);
+#ifdef FEAT_EVAL
+    restore_v_event(v_event, &save_v_event);
+#endif
+}
+
 /*
  * Change directory function used by :cd/:tcd/:lcd Ex commands and the
  * chdir() function.
@@ -7358,7 +7378,7 @@ changedir_func(
 {
     char_u	*pdir = NULL;
     int		dir_differs;
-    char_u	*acmd_fname;
+    char_u	*acmd_fname = NULL;
     char_u	**pp;
 
     if (new_dir == NULL || allbuf_locked())
@@ -7412,12 +7432,23 @@ changedir_func(
     }
     dir_differs = pdir == NULL
 			    || pathcmp((char *)pdir, (char *)new_dir, -1) != 0;
-    if (dir_differs && vim_chdir(new_dir))
+    if (dir_differs)
+    {
+	if (scope == CDSCOPE_WINDOW)
+	    acmd_fname = (char_u *)"window";
+	else if (scope == CDSCOPE_TABPAGE)
+	    acmd_fname = (char_u *)"tabpage";
+	else
+	    acmd_fname = (char_u *)"global";
+	trigger_DirChangedPre(acmd_fname, new_dir);
+
+	if (vim_chdir(new_dir))
 	{
 	    emsg(_(e_command_failed));
 	    vim_free(pdir);
 	    return FALSE;
 	}
+    }
 
     if (scope == CDSCOPE_WINDOW)
 	pp = &curwin->w_prevdir;
@@ -7431,16 +7462,7 @@ changedir_func(
     post_chdir(scope);
 
     if (dir_differs)
-    {
-	if (scope == CDSCOPE_WINDOW)
-	    acmd_fname = (char_u *)"window";
-	else if (scope == CDSCOPE_TABPAGE)
-	    acmd_fname = (char_u *)"tabpage";
-	else
-	    acmd_fname = (char_u *)"global";
-	apply_autocmds(EVENT_DIRCHANGED, acmd_fname, new_dir, FALSE,
-							    curbuf);
-    }
+	apply_autocmds(EVENT_DIRCHANGED, acmd_fname, new_dir, FALSE, curbuf);
     return TRUE;
 }
 

src/misc2.c

@@ -1914,6 +1914,9 @@ vim_chdirfile(char_u *fname, char *trigger_autocmd)
 	// nothing to do
 	return OK;
 
+    if (trigger_autocmd != NULL)
+	trigger_DirChangedPre((char_u *)trigger_autocmd, new_dir);
+
     if (mch_chdir((char *)new_dir) != 0)
 	return FAIL;
 

src/proto/ex_docmd.pro

@@ -48,6 +48,7 @@ void tabpage_new(void);
 void do_exedit(exarg_T *eap, win_T *old_curwin);
 void free_cd_dir(void);
 void post_chdir(cdscope_T scope);
+void trigger_DirChangedPre(char_u *acmd_fname, char_u *new_dir);
 int changedir_func(char_u *new_dir, int forceit, cdscope_T scope);
 void ex_cd(exarg_T *eap);
 void do_sleep(long msec, int hide_cursor);

src/testdir/test_autocmd.vim

@@ -1922,14 +1922,16 @@ endfunc
 
 function Test_dirchanged_global()
   call s:Before_test_dirchanged()
+  autocmd test_dirchanged DirChangedPre global call add(s:li, "pre cd " .. v:event.directory)
   autocmd test_dirchanged DirChanged global call add(s:li, "cd:")
   autocmd test_dirchanged DirChanged global call add(s:li, expand("<afile>"))
   call chdir(s:dir_foo)
-  call assert_equal(["cd:", s:dir_foo], s:li)
+  let expected = ["pre cd " .. s:dir_foo, "cd:", s:dir_foo]
+  call assert_equal(expected, s:li)
   call chdir(s:dir_foo)
-  call assert_equal(["cd:", s:dir_foo], s:li)
+  call assert_equal(expected, s:li)
   exe 'lcd ' .. fnameescape(s:dir_bar)
-  call assert_equal(["cd:", s:dir_foo], s:li)
+  call assert_equal(expected, s:li)
   call s:After_test_dirchanged()
 endfunc
 
@@ -1950,6 +1952,7 @@ function Test_dirchanged_auto()
   CheckOption autochdir
   call s:Before_test_dirchanged()
   call test_autochdir()
+  autocmd test_dirchanged DirChangedPre auto call add(s:li, "pre cd " .. v:event.directory)
   autocmd test_dirchanged DirChanged auto call add(s:li, "auto:")
   autocmd test_dirchanged DirChanged auto call add(s:li, expand("<afile>"))
   set acd
@@ -1957,7 +1960,8 @@ function Test_dirchanged_auto()
   call assert_equal([], s:li)
   exe 'edit ' . s:dir_foo . '/Xfile'
   call assert_equal(s:dir_foo, getcwd())
-  call assert_equal(["auto:", s:dir_foo], s:li)
+  let expected = ["pre cd " .. s:dir_foo, "auto:", s:dir_foo]
+  call assert_equal(expected, s:li)
   set noacd
   bwipe!
   call s:After_test_dirchanged()

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4335,
 /**/
     4334,
 /**/

src/vim.h

@@ -1304,6 +1304,7 @@ enum auto_event
     EVENT_CURSORMOVEDI,		// cursor was moved in Insert mode
     EVENT_DIFFUPDATED,		// after diffs were updated
     EVENT_DIRCHANGED,		// after user changed directory
+    EVENT_DIRCHANGEDPRE,	// before directory changes
     EVENT_ENCODINGCHANGED,	// after changing the 'encoding' option
     EVENT_EXITPRE,		// before exiting
     EVENT_FILEAPPENDCMD,	// append to a file using command