vim-patch:8.0.0580: cannot set the valid flag with setqflist()

Problem:    Cannot set the valid flag with setqflist().
Solution:   Add the "valid" argument. (Yegappan Lakshmanan, closes vim/vim#1642)

f1d21c8cc8

runtime/doc/eval.txt

@@ -6841,6 +6841,7 @@ setqflist({list} [, {action}[, {what}]])		*setqflist()*
 		    nr		error number
 		    text	description of the error
 		    type	single-character error type, 'E', 'W', etc.
+		    valid	recognized error message
 
 		The "col", "vcol", "nr", "type" and "text" entries are
 		optional.  Either "lnum" or "pattern" entry can be used to
@@ -6850,6 +6851,8 @@ setqflist({list} [, {action}[, {what}]])		*setqflist()*
 		item will not be handled as an error line.
 		If both "pattern" and "lnum" are present then "pattern" will
 		be used.
+		If the "valid" entry is not supplied, then the valid flag is
+		set when "bufnr" is a valid buffer or "filename" exists.
 		If you supply an empty {list}, the quickfix list will be
 		cleared.
 		Note that the list is not exactly the same as what

src/nvim/quickfix.c

@@ -4189,6 +4189,11 @@ static int qf_add_entries(qf_info_T *qi, list_T *list, char_u *title,
       bufnum = 0;
     }
 
+    // If the 'valid' field is present it overrules the detected value.
+    if (tv_dict_find(d, "valid", -1) != NULL) {
+      valid = (int)tv_dict_get_number(d, "valid");
+    }
+
     int status = qf_add_entry(qi,
                               NULL,      // dir
                               (char_u *)filename,

src/nvim/testdir/test_quickfix.vim

@@ -1183,6 +1183,25 @@ func SetXlistTests(cchar, bnum)
   let l = g:Xgetlist()
   call assert_equal(0, len(l))
 
+  " Tests for setting the 'valid' flag
+  call g:Xsetlist([{'bufnr':a:bnum, 'lnum':4, 'valid':0}])
+  Xwindow
+  call assert_equal(1, winnr('$'))
+  let l = g:Xgetlist()
+  call g:Xsetlist(l)
+  call assert_equal(0, g:Xgetlist()[0].valid)
+  call g:Xsetlist([{'text':'Text1', 'valid':1}])
+  Xwindow
+  call assert_equal(2, winnr('$'))
+  Xclose
+  let save_efm = &efm
+  set efm=%m
+  Xgetexpr 'TestMessage'
+  let l = g:Xgetlist()
+  call g:Xsetlist(l)
+  call assert_equal(1, g:Xgetlist()[0].valid)
+  let &efm = save_efm
+
   " Error cases:
   " Refer to a non-existing buffer and pass a non-dictionary type
   call assert_fails("call g:Xsetlist([{'bufnr':998, 'lnum':4}," .