patch 8.0.1023: it is not easy to identify a quickfix list

Problem:    It is not easy to identify a quickfix list.
Solution:   Add the "id" field. (Yegappan Lakshmanan)

runtime/doc/eval.txt

@@ -4632,6 +4632,9 @@ getqflist([{what}])					*getqflist()*
 		returns only the items listed in {what} as a dictionary. The
 		following string items are supported in {what}:
 			context	get the context stored with |setqflist()|
+			id	get information for the quickfix list with
+				|quickfix-ID|; zero means the id for the
+				current list or the list specifed by 'nr'
 			items	quickfix list entries
 			nr	get information for this quickfix list; zero
 				means the current quickfix list and '$' means
@@ -4646,6 +4649,8 @@ getqflist([{what}])					*getqflist()*
 			all	all of the above quickfix properties
 		Non-string items in {what} are ignored.
 		If "nr" is not present then the current quickfix list is used.
+		If both "nr" and a non-zero "id" are specified, then the list
+		specified by "id" is used.
 		To get the number of lists in the quickfix stack, set 'nr' to
 		'$' in {what}. The 'nr' value in the returned dictionary
 		contains the quickfix stack size.
@@ -4657,6 +4662,7 @@ getqflist([{what}])					*getqflist()*
 
 		The returned dictionary contains the following entries:
 			context	context information stored with |setqflist()|
+			id	quickfix list ID |quickfix-ID|
 			items	quickfix list entries
 			nr	quickfix list number
 			title	quickfix list title text
@@ -7069,6 +7075,7 @@ setqflist({list} [, {action}[, {what}]])		*setqflist()*
 				text and add the resulting entries to the
 				quickfix list {nr}.  The value can be a string
 				with one line or a list with multiple lines.
+		    id		quickfix list identifier |quickfix-ID|
 		    items	list of quickfix entries. Same as the {list}
 				argument.
 		    nr		list number in the quickfix stack; zero
@@ -7079,6 +7086,9 @@ setqflist({list} [, {action}[, {what}]])		*setqflist()*
 		If the "nr" item is not present, then the current quickfix list
 		is modified. When creating a new quickfix list, "nr" can be
 		set to a value one greater than the quickfix stack size.
+		When modifying a quickfix list, to guarantee that the correct
+		list is modified, 'id' should be used instead of 'nr' to
+		specify the list.
 
 		Examples: >
 			:call setqflist([], 'r', {'title': 'My search'})

src/quickfix.c

@@ -58,6 +58,7 @@ struct qfline_S
  */
 typedef struct qf_list_S
 {
+    int_u	qf_id;		/* Unique identifier for this list */
     qfline_T	*qf_start;	/* pointer to the first error */
     qfline_T	*qf_last;	/* pointer to the last error */
     qfline_T	*qf_ptr;	/* pointer to the current error */
@@ -96,6 +97,7 @@ struct qf_info_S
 };
 
 static qf_info_T ql_info;	/* global quickfix list */
+static int_u last_qf_id = 0;	/* Last used quickfix list id */
 
 #define FMT_PATTERNS 10		/* maximum number of % recognized */
 
@@ -1399,6 +1401,7 @@ qf_new_list(qf_info_T *qi, char_u *qf_title)
 	qi->qf_curlist = qi->qf_listcount++;
     vim_memset(&qi->qf_lists[qi->qf_curlist], 0, (size_t)(sizeof(qf_list_T)));
     qf_store_title(qi, qi->qf_curlist, qf_title);
+    qi->qf_lists[qi->qf_curlist].qf_id = ++last_qf_id;
 }
 
 /*
@@ -1672,6 +1675,9 @@ copy_loclist(win_T *from, win_T *to)
 
 	to_qfl->qf_index = from_qfl->qf_index;	/* current index in the list */
 
+	/* Assign a new ID for the location list */
+	to_qfl->qf_id = ++last_qf_id;
+
 	/* When no valid entries are present in the list, qf_ptr points to
 	 * the first item in the list */
 	if (to_qfl->qf_nonevalid)
@@ -2808,6 +2814,7 @@ qf_free(qf_info_T *qi, int idx)
     qfl->qf_title = NULL;
     free_tv(qfl->qf_ctx);
     qfl->qf_ctx = NULL;
+    qfl->qf_id = 0;
 }
 
 /*
@@ -4628,6 +4635,7 @@ enum {
     QF_GETLIST_NR	= 0x4,
     QF_GETLIST_WINID	= 0x8,
     QF_GETLIST_CONTEXT	= 0x10,
+    QF_GETLIST_ID	= 0x20,
     QF_GETLIST_ALL	= 0xFF
 };
 
@@ -4688,18 +4696,18 @@ get_errorlist_properties(win_T *wp, dict_T *what, dict_T *retdict)
 	return qf_get_list_from_text(di, retdict);
 
     if (wp != NULL)
-    {
 	qi = GET_LOC_LIST(wp);
-	if (qi == NULL)
+
+    /* List is not present or is empty */
+    if (qi == NULL || qi->qf_listcount == 0)
     {
-	    /* If querying for the size of the location list, return 0 */
+	/* If querying for the size of the list, return 0 */
 	if (((di = dict_find(what, (char_u *)"nr", -1)) != NULL)
 		&& (di->di_tv.v_type == VAR_STRING)
 		&& (STRCMP(di->di_tv.vval.v_string, "$") == 0))
 	    return dict_add_nr_str(retdict, "nr", 0, NULL);
 	return FAIL;
     }
-    }
 
     qf_idx = qi->qf_curlist;		/* default is the current list */
     if ((di = dict_find(what, (char_u *)"nr", -1)) != NULL)
@@ -4714,26 +4722,38 @@ get_errorlist_properties(win_T *wp, dict_T *what, dict_T *retdict)
 		if (qf_idx < 0 || qf_idx >= qi->qf_listcount)
 		    return FAIL;
 	    }
-	    else if (qi->qf_listcount == 0)	    /* stack is empty */
-		return FAIL;
-	    flags |= QF_GETLIST_NR;
 	}
 	else if ((di->di_tv.v_type == VAR_STRING)
 		&& (STRCMP(di->di_tv.vval.v_string, "$") == 0))
-	{
 	    /* Get the last quickfix list number */
-	    if (qi->qf_listcount > 0)
 	    qf_idx = qi->qf_listcount - 1;
 	else
-		qf_idx = -1;	/* Quickfix stack is empty */
+	    return FAIL;
 	flags |= QF_GETLIST_NR;
     }
+
+    if ((di = dict_find(what, (char_u *)"id", -1)) != NULL)
+    {
+	/* Look for a list with the specified id */
+	if (di->di_tv.v_type == VAR_NUMBER)
+	{
+	    /* For zero, use the current list or the list specifed by 'nr' */
+	    if (di->di_tv.vval.v_number != 0)
+	    {
+		for (qf_idx = 0; qf_idx < qi->qf_listcount; qf_idx++)
+		{
+		    if (qi->qf_lists[qf_idx].qf_id == di->di_tv.vval.v_number)
+			break;
+		}
+		if (qf_idx == qi->qf_listcount)
+		    return FAIL;	    /* List not found */
+	    }
+	    flags |= QF_GETLIST_ID;
+	}
 	else
 	    return FAIL;
     }
 
-    if (qf_idx != -1)
-    {
     if (dict_find(what, (char_u *)"all", -1) != NULL)
 	flags |= QF_GETLIST_ALL;
 
@@ -4748,7 +4768,6 @@ get_errorlist_properties(win_T *wp, dict_T *what, dict_T *retdict)
 
     if (dict_find(what, (char_u *)"items", -1) != NULL)
 	flags |= QF_GETLIST_ITEMS;
-    }
 
     if (flags & QF_GETLIST_TITLE)
     {
@@ -4798,6 +4817,10 @@ get_errorlist_properties(win_T *wp, dict_T *what, dict_T *retdict)
 	    status = dict_add_nr_str(retdict, "context", 0L, (char_u *)"");
     }
 
+    if ((status == OK) && (flags & QF_GETLIST_ID))
+	status = dict_add_nr_str(retdict, "id", qi->qf_lists[qf_idx].qf_id,
+									 NULL);
+
     return status;
 }
 
@@ -4983,6 +5006,21 @@ qf_set_properties(qf_info_T *qi, dict_T *what, int action, char_u *title)
 	    return FAIL;
     }
 
+    if (!newlist && (di = dict_find(what, (char_u *)"id", -1)) != NULL)
+    {
+	/* Use the quickfix/location list with the specified id */
+	if (di->di_tv.v_type == VAR_NUMBER)
+	{
+	    for (qf_idx = 0; qf_idx < qi->qf_listcount; qf_idx++)
+		if (qi->qf_lists[qf_idx].qf_id == di->di_tv.vval.v_number)
+		    break;
+	    if (qf_idx == qi->qf_listcount)
+		return FAIL;	    /* List not found */
+	}
+	else
+	    return FAIL;
+    }
+
     if (newlist)
     {
 	qi->qf_curlist = qf_idx;

src/testdir/test_quickfix.vim

@@ -1897,8 +1897,9 @@ func Xproperty_tests(cchar)
     call g:Xsetlist([], 'r', {'nr':2,'title':'Fruits','context':['Fruits']})
     let l1=g:Xgetlist({'nr':1,'all':1})
     let l2=g:Xgetlist({'nr':2,'all':1})
-    let l1.nr=2
+    let save_id = l1.id
-    let l2.nr=1
+    let l1.id=l2.id
+    let l2.id=save_id
     call g:Xsetlist([], 'r', l1)
     call g:Xsetlist([], 'r', l2)
     let newl1=g:Xgetlist({'nr':1,'all':1})
@@ -2545,3 +2546,38 @@ func Test_get_list_from_text()
   call XgetListFromText('c')
   call XgetListFromText('l')
 endfunc
+
+" Tests for the quickfix list id
+func Xqfid_tests(cchar)
+  call s:setup_commands(a:cchar)
+
+  call g:Xsetlist([], 'f')
+  call assert_equal({}, g:Xgetlist({'id':0}))
+  Xexpr ''
+  let start_id = g:Xgetlist({'id' : 0}).id
+  Xexpr '' | Xexpr ''
+  Xolder
+  call assert_equal(start_id, g:Xgetlist({'id':0, 'nr':1}).id)
+  call assert_equal(start_id + 1, g:Xgetlist({'id':0, 'nr':0}).id)
+  call assert_equal(start_id + 2, g:Xgetlist({'id':0, 'nr':'$'}).id)
+  call assert_equal({}, g:Xgetlist({'id':0, 'nr':99}))
+  call assert_equal(2, g:Xgetlist({'id':start_id + 1, 'nr':0}).nr)
+  call assert_equal({}, g:Xgetlist({'id':99, 'nr':0}))
+  call assert_equal({}, g:Xgetlist({'id':"abc", 'nr':0}))
+
+  call g:Xsetlist([], 'a', {'id':start_id, 'context':[1,2]})
+  call assert_equal([1,2], g:Xgetlist({'nr':1, 'context':1}).context)
+  call g:Xsetlist([], 'a', {'id':start_id+1, 'text':'F1:10:L10'})
+  call assert_equal('L10', g:Xgetlist({'nr':2, 'items':1}).items[0].text)
+  call assert_equal(-1, g:Xsetlist([], 'a', {'id':999, 'title':'Vim'}))
+  call assert_equal(-1, g:Xsetlist([], 'a', {'id':'abc', 'title':'Vim'}))
+
+  let qfid = g:Xgetlist({'id':0, 'nr':0})
+  call g:Xsetlist([], 'f')
+  call assert_equal({}, g:Xgetlist({'id':qfid, 'nr':0}))
+endfunc
+
+func Test_qf_id()
+  call Xqfid_tests('c')
+  call Xqfid_tests('l')
+endfunc

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1023,
 /**/
     1022,
 /**/