patch 8.0.0177: BufEnter autocommand not fired for a directory

Problem:    When opening a buffer on a directory and inside a try/catch then
            the BufEnter event is not triggered.
Solution:   Return NOTDONE from readfile() for a directory and deal with the
            three possible return values. (Justin M. Keyes, closes #1375,
            closes #1353)

src/buffer.c

@@ -113,16 +113,19 @@ read_buffer(
 	 * it can be changed there. */
 	if (!readonlymode && !bufempty())
 	    changed();
-	else if (retval != FAIL)
+	else if (retval == OK)
 	    unchanged(curbuf, FALSE);
 
 #ifdef FEAT_AUTOCMD
+	if (retval == OK)
+	{
 # ifdef FEAT_EVAL
-	apply_autocmds_retval(EVENT_STDINREADPOST, NULL, NULL, FALSE,
+	    apply_autocmds_retval(EVENT_STDINREADPOST, NULL, NULL, FALSE,
 							curbuf, &retval);
 # else
-	apply_autocmds(EVENT_STDINREADPOST, NULL, NULL, FALSE, curbuf);
+	    apply_autocmds(EVENT_STDINREADPOST, NULL, NULL, FALSE, curbuf);
 # endif
+	}
 #endif
     }
     return retval;
@@ -294,7 +297,7 @@ open_buffer(
 #endif
        )
 	changed();
-    else if (retval != FAIL && !read_stdin && !read_fifo)
+    else if (retval == OK && !read_stdin && !read_fifo)
 	unchanged(curbuf, FALSE);
     save_file_ff(curbuf);		/* keep this fileformat */
 
@@ -328,7 +331,7 @@ open_buffer(
 # endif
 #endif
 
-    if (retval != FAIL)
+    if (retval == OK)
     {
 #ifdef FEAT_AUTOCMD
 	/*

src/ex_cmds.c

@@ -1313,7 +1313,7 @@ do_filter(
 	if (otmp != NULL)
 	{
 	    if (readfile(otmp, NULL, line2, (linenr_T)0, (linenr_T)MAXLNUM,
-						    eap, READ_FILTER) == FAIL)
+						    eap, READ_FILTER) != OK)
 	    {
 #if defined(FEAT_AUTOCMD) && defined(FEAT_EVAL)
 		if (!aborting())

src/ex_docmd.c

@@ -8857,7 +8857,7 @@ ex_read(exarg_T *eap)
 			  eap->line2, (linenr_T)0, (linenr_T)MAXLNUM, eap, 0);
 
 	}
-	if (i == FAIL)
+	if (i != OK)
 	{
 #if defined(FEAT_AUTOCMD) && defined(FEAT_EVAL)
 	    if (!aborting())

src/fileio.c

@@ -210,7 +210,7 @@ filemess(
  * READ_KEEP_UNDO  don't clear undo info or read it from a file
  * READ_FIFO	read from fifo/socket instead of a file
  *
- * return FAIL for failure, OK otherwise
+ * return FAIL for failure, NOTDONE for directory (failure), or OK
  */
     int
 readfile(
@@ -450,13 +450,18 @@ readfile(
 # endif
 						)
 	{
+	    int retval = FAIL;
+
 	    if (S_ISDIR(perm))
+	    {
 		filemess(curbuf, fname, (char_u *)_("is a directory"), 0);
+		retval = NOTDONE;
+	    }
 	    else
 		filemess(curbuf, fname, (char_u *)_("is not a file"), 0);
 	    msg_end();
 	    msg_scroll = msg_save;
-	    return FAIL;
+	    return retval;
 	}
 #endif
 #if defined(MSWIN)
@@ -7136,7 +7141,7 @@ buf_reload(buf_T *buf, int orig_mode)
 #endif
 	    if (readfile(buf->b_ffname, buf->b_fname, (linenr_T)0,
 			(linenr_T)0,
-			(linenr_T)MAXLNUM, &ea, flags) == FAIL)
+			(linenr_T)MAXLNUM, &ea, flags) != OK)
 	    {
 #if defined(FEAT_AUTOCMD) && defined(FEAT_EVAL)
 		if (!aborting())

src/memline.c

@@ -1519,7 +1519,7 @@ ml_recover(void)
 			    line_count = pp->pb_pointer[idx].pe_line_count;
 			    if (readfile(curbuf->b_ffname, NULL, lnum,
 					pp->pb_pointer[idx].pe_old_lnum - 1,
-					line_count, NULL, 0) == FAIL)
+					line_count, NULL, 0) != OK)
 				cannot_open = TRUE;
 			    else
 				lnum += line_count;

src/testdir/test_autocmd.vim

@@ -322,3 +322,22 @@ func Test_three_windows()
   call delete('Xtestje2')
   call delete('Xtestje3')
 endfunc
+
+func Test_BufEnter()
+  au! BufEnter
+  au Bufenter * let val = val . '+'
+  let g:val = ''
+  split NewFile
+  call assert_equal('+', g:val)
+  bwipe!
+  call assert_equal('++', g:val)
+
+  " Also get BufEnter when editing a directory
+  call mkdir('Xdir')
+  split Xdir
+  call assert_equal('+++', g:val)
+  bwipe!
+
+  call delete('Xdir', 'd')
+  au! BufEnter
+endfunc

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    177,
 /**/
     176,
 /**/