From 9606317486416aeba590d44fd9fcc955834d1e3b Mon Sep 17 00:00:00 2001
From: Jan Edmund Lazo <jan.lazo@mail.utoronto.ca>
Date: Sat, 10 Oct 2020 15:22:05 -0400
Subject: [PATCH] vim-patch:8.1.0988: deleting location list buffer breaks
 location list window

Problem:    Deleting a location list buffer breaks location list window
            functionality.
Solution:   (Yegappan Lakshmanan, closes vim/vim#4056)
https://github.com/vim/vim/commit/d82a81cad93708a6c180e59119db4818cc38c1a9

Cherry-pick Xqbuf_test() changes from patch 8.1.0892.
Patch 8.1.0892 triggers a memory leak.
---
 src/nvim/quickfix.c                | 26 +++++++++++++++++------
 src/nvim/testdir/test_quickfix.vim | 34 +++++++++++++++++++++++++++++-
 2 files changed, 52 insertions(+), 8 deletions(-)

diff --git a/src/nvim/quickfix.c b/src/nvim/quickfix.c
index 1582ce3bd6..06fed9c2cf 100644
--- a/src/nvim/quickfix.c
+++ b/src/nvim/quickfix.c
@@ -3581,6 +3581,18 @@ static int qf_goto_cwindow(const qf_info_T *qi, bool resize, int sz,
   return OK;
 }
 
+// Set options for the buffer in the quickfix or location list window.
+static void qf_set_cwindow_options(void)
+{
+  // switch off 'swapfile'
+  set_option_value("swf", 0L, NULL, OPT_LOCAL);
+  set_option_value("bt", 0L, "quickfix", OPT_LOCAL);
+  set_option_value("bh", 0L, "hide", OPT_LOCAL);
+  RESET_BINDING(curwin);
+  curwin->w_p_diff = false;
+  set_option_value("fdm", 0L, "manual", OPT_LOCAL);
+}
+
 // Open a new quickfix or location list window, load the quickfix buffer and
 // set the appropriate options for the window.
 // Returns FAIL if the window could not be opened.
@@ -3629,17 +3641,17 @@ static int qf_open_new_cwindow(qf_info_T *qi, int height)
     // Create a new quickfix buffer
     (void)do_ecmd(0, NULL, NULL, NULL, ECMD_ONE, ECMD_HIDE, oldwin);
 
-    // switch off 'swapfile'
-    set_option_value("swf", 0L, NULL, OPT_LOCAL);
-    set_option_value("bt", 0L, "quickfix", OPT_LOCAL);
-    set_option_value("bh", 0L, "hide", OPT_LOCAL);
-    RESET_BINDING(curwin);
-    curwin->w_p_diff = false;
-    set_option_value("fdm", 0L, "manual", OPT_LOCAL);
     // save the number of the new buffer
     qi->qf_bufnr = curbuf->b_fnum;
   }
 
+  // Set the options for the quickfix buffer/window (if not already done)
+  // Do this even if the quickfix buffer was already present, as an autocmd
+  // might have previously deleted (:bdelete) the quickfix buffer.
+  if (curbuf->b_p_bt[0] != 'q') {
+    qf_set_cwindow_options();
+  }
+
   // Only set the height when still in the same tab page and there is no
   // window to the side.
   if (curtab == prevtab && curwin->w_width == Columns) {
diff --git a/src/nvim/testdir/test_quickfix.vim b/src/nvim/testdir/test_quickfix.vim
index d7eb4806ec..dc1b20ce65 100644
--- a/src/nvim/testdir/test_quickfix.vim
+++ b/src/nvim/testdir/test_quickfix.vim
@@ -4061,8 +4061,40 @@ func Xqfbuf_test(cchar)
     call assert_match(qfbnum . '  h-  "\[Location List]"', execute('ls'))
     call assert_true(bufloaded(qfbnum))
 
+    " After deleting a location list buffer using ":bdelete", opening the
+    " location list window should mark the buffer as a location list buffer.
+    exe "bdelete " . qfbnum
+    lopen
+    call assert_equal("quickfix", &buftype)
+    call assert_equal(1, getwininfo(win_getid(winnr()))[0].loclist)
+    call assert_equal(wid, getloclist(0, {'filewinid' : 0}).filewinid)
+    call assert_false(&swapfile)
+    lclose
+
+    " When the location list is cleared for the window, the buffer should be
+    " removed
+    call setloclist(0, [], 'f')
+    call assert_false(bufexists(qfbnum))
+
+    " When the location list is freed with the location list window open, the
+    " location list buffer should not be lost. It should be reused when the
+    " location list is again populated.
+    lexpr "F1:10:Line10"
+    lopen
+    let wid = win_getid()
+    let qfbnum = bufnr('')
+    wincmd p
+    call setloclist(0, [], 'f')
+    lexpr "F1:10:Line10"
+    lopen
+    call assert_equal(wid, win_getid())
+    call assert_equal(qfbnum, bufnr(''))
+    lclose
+
+    " When the window with the location list is closed, the buffer should be
+    " removed
     new | only
-    call assert_false(bufloaded(qfbnum))
+    call assert_false(bufexists(qfbnum))
   endif
 endfunc