patch 8.0.0860: side effects when channel appends to a buffer

Problem:    There may be side effects when a channel appends to a buffer that
            is not the current buffer.
Solution:   Properly switch to another buffer before appending. (Yasuhiro
            Matsumoto, closes #1926, closes #1937)

src/buffer.c

@@ -5794,9 +5794,52 @@ buf_spname(buf_T *buf)
     return NULL;
 }
 
-#if (defined(FEAT_QUICKFIX) && defined(FEAT_WINDOWS)) \
+#if defined(FEAT_JOB_CHANNEL) \
 	|| defined(FEAT_PYTHON) || defined(FEAT_PYTHON3) \
 	|| defined(PROTO)
+# define SWITCH_TO_WIN
+
+/*
+ * Find a window that contains "buf" and switch to it.
+ * If there is no such window, use the current window and change "curbuf".
+ * Caller must initialize save_curbuf to NULL.
+ * restore_win_for_buf() MUST be called later!
+ */
+    void
+switch_to_win_for_buf(
+    buf_T	*buf,
+    win_T	**save_curwinp,
+    tabpage_T	**save_curtabp,
+    bufref_T	*save_curbuf)
+{
+    win_T	*wp;
+    tabpage_T	*tp;
+
+    if (find_win_for_buf(buf, &wp, &tp) == FAIL)
+	switch_buffer(save_curbuf, buf);
+    else if (switch_win(save_curwinp, save_curtabp, wp, tp, TRUE) == FAIL)
+    {
+	restore_win(*save_curwinp, *save_curtabp, TRUE);
+	switch_buffer(save_curbuf, buf);
+    }
+}
+
+    void
+restore_win_for_buf(
+    win_T	*save_curwin,
+    tabpage_T	*save_curtab,
+    bufref_T	*save_curbuf)
+{
+    if (save_curbuf->br_buf == NULL)
+	restore_win(save_curwin, save_curtab, TRUE);
+    else
+	restore_buffer(save_curbuf);
+}
+#endif
+
+#if (defined(FEAT_QUICKFIX) && defined(FEAT_WINDOWS)) \
+	|| defined(SWITCH_TO_WIN) \
+	|| defined(PROTO)
 /*
  * Find a window for buffer "buf".
  * If found OK is returned and "wp" and "tp" are set to the window and tabpage.

src/channel.c

@@ -2284,7 +2284,9 @@ invoke_one_time_callback(
     static void
 append_to_buffer(buf_T *buffer, char_u *msg, channel_T *channel, ch_part_T part)
 {
-    buf_T	*save_curbuf = curbuf;
+    bufref_T	save_curbuf = {NULL, 0, 0};
+    win_T	*save_curwin = NULL;
+    tabpage_T	*save_curtab = NULL;
     linenr_T    lnum = buffer->b_ml.ml_line_count;
     int		save_write_to = buffer->b_write_to_channel;
     chanpart_T  *ch_part = &channel->ch_part[part];
@@ -2313,8 +2315,10 @@ append_to_buffer(buf_T *buffer, char_u *msg, channel_T *channel, ch_part_T part)
     ch_log(channel, "appending line %d to buffer", (int)lnum + 1 - empty);
 
     buffer->b_p_ma = TRUE;
-    curbuf = buffer;
+
-    curwin->w_buffer = curbuf;
+    /* Save curbuf/curwin/curtab and make "buffer" the current buffer. */
+    switch_to_win_for_buf(buffer, &save_curwin, &save_curtab, &save_curbuf);
+
     u_sync(TRUE);
     /* ignore undo failure, undo is not very useful here */
     ignored = u_save(lnum - empty, lnum + 1);
@@ -2328,8 +2332,10 @@ append_to_buffer(buf_T *buffer, char_u *msg, channel_T *channel, ch_part_T part)
     else
 	ml_append(lnum, msg, 0, FALSE);
     appended_lines_mark(lnum, 1L);
-    curbuf = save_curbuf;
+
-    curwin->w_buffer = curbuf;
+    /* Restore curbuf/curwin/curtab */
+    restore_win_for_buf(save_curwin, save_curtab, &save_curbuf);
+
     if (ch_part->ch_nomodifiable)
 	buffer->b_p_ma = FALSE;
     else
@@ -2338,7 +2344,6 @@ append_to_buffer(buf_T *buffer, char_u *msg, channel_T *channel, ch_part_T part)
     if (buffer->b_nwindows > 0)
     {
 	win_T	*wp;
-	win_T	*save_curwin;
 
 	FOR_ALL_WINDOWS(wp)
 	{

src/if_py_both.h

@@ -4262,43 +4262,6 @@ py_fix_cursor(linenr_T lo, linenr_T hi, linenr_T extra)
     invalidate_botline();
 }
 
-/*
- * Find a window that contains "buf" and switch to it.
- * If there is no such window, use the current window and change "curbuf".
- * Caller must initialize save_curbuf to NULL.
- * restore_win_for_buf() MUST be called later!
- */
-    static void
-switch_to_win_for_buf(
-    buf_T	*buf,
-    win_T	**save_curwinp,
-    tabpage_T	**save_curtabp,
-    bufref_T	*save_curbuf)
-{
-    win_T	*wp;
-    tabpage_T	*tp;
-
-    if (find_win_for_buf(buf, &wp, &tp) == FAIL)
-	switch_buffer(save_curbuf, buf);
-    else if (switch_win(save_curwinp, save_curtabp, wp, tp, TRUE) == FAIL)
-    {
-	restore_win(*save_curwinp, *save_curtabp, TRUE);
-	switch_buffer(save_curbuf, buf);
-    }
-}
-
-    static void
-restore_win_for_buf(
-    win_T	*save_curwin,
-    tabpage_T	*save_curtab,
-    bufref_T	*save_curbuf)
-{
-    if (save_curbuf->br_buf == NULL)
-	restore_win(save_curwin, save_curtab, TRUE);
-    else
-	restore_buffer(save_curbuf);
-}
-
 /*
  * Replace a line in the specified buffer. The line number is
  * in Vim format (1-based). The replacement line is given as

src/proto/buffer.pro

@@ -61,6 +61,8 @@ int bt_dontwrite(buf_T *buf);
 int bt_dontwrite_msg(buf_T *buf);
 int buf_hide(buf_T *buf);
 char_u *buf_spname(buf_T *buf);
+void switch_to_win_for_buf(buf_T *buf, win_T **save_curwinp, tabpage_T **save_curtabp, bufref_T *save_curbuf);
+void restore_win_for_buf(win_T *save_curwin, tabpage_T *save_curtab, bufref_T *save_curbuf);
 int find_win_for_buf(buf_T *buf, win_T **wp, tabpage_T **tp);
 void buf_addsign(buf_T *buf, int id, linenr_T lnum, int typenr);
 linenr_T buf_change_sign_type(buf_T *buf, int markId, int typenr);

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    860,
 /**/
     859,
 /**/