Do not create recurring tasks before today

Tasks can be due "today", as `task add foo due:today ..` is a common
form. However, recurrences before that are just not created.

This avoids a lengthy "hang" when recurrences are updated on an old task
database, as many tasks in the past are created.

src/recur.cpp

@@ -135,9 +135,10 @@ void handleRecurrence ()
 
 ////////////////////////////////////////////////////////////////////////////////
 // Determine a start date (due), an optional end date (until), and an increment
-// period (recur).  Then generate a set of corresponding dates.
+// period (recur).  Then generate a set of corresponding dates. Only recurrences
+// in the future are returned; see #3501.
 //
-// Returns false if the parent recurring task is depleted.
+// Returns false if the parent recurring task is deleted.
 bool generateDueDates (Task& parent, std::vector <Datetime>& allDue)
 {
   // Determine due date, recur period and until date.
@@ -158,9 +159,12 @@ bool generateDueDates (Task& parent, std::vector <Datetime>& allDue)
   auto recurrence_limit = Context::getContext ().config.getInteger ("recurrence.limit");
   int recurrence_counter = 0;
   Datetime now;
+  Datetime today = now.startOfDay();
   for (Datetime i = due; ; i = getNextRecurrence (i, recur))
   {
-    allDue.push_back (i);
+    // Do not add tasks before today (but allow today for the common `due:today` form).
+    if (i >= today)
+      allDue.push_back (i);
 
     if (specificEnd && i > until)
     {

test/recurrence.test.py

@@ -289,14 +289,15 @@ def setUp(self):
         self.t = Task()
         self.t.config("report.id_pri_proj.columns", "id,priority,project")
         self.t.config("report.id_pri_proj.labels", "ID,P,Proj")
+        self.t.config("recurrence.limit", "3")
 
     def test_modify_due_propagate(self):
         """932: Verify due date modifications propagate"""
 
         # add a recurring task with multiple child tasks
         # - modify a child task and test for propagation
         # - modify the parent task and test for propagation
-        self.t("add R due:yesterday recur:daily")
+        self.t("add R due:tomorrow recur:daily")
         self.t("list")  # GC/handleRecurrence
 
         self.t("2 modify project:P", input="y\n")
@@ -316,7 +317,8 @@ class TestBug955(TestCase):
     def setUp(self):
         self.t = Task()
 
-        self.t("add foo due:now recur:1day")
+        self.t.config("recurrence.limit", "2")
+        self.t("add foo due:tomorrow recur:1day")
         code, out, err = self.t("ls")
         self.assertRegex(out, re.compile("^2 tasks", re.MULTILINE))
 
@@ -612,47 +614,52 @@ def setUp(self):
 
     def test_annual_creep(self):
         """Verify 'annual' recurring tasks don't creep"""
+        self.t.config("recurrence.limit", "17")
         self.t.config("dateformat",            "YMD")
         self.t.config("report.annual.labels",  "ID,Due")
         self.t.config("report.annual.columns", "id,due")
         self.t.config("report.annual.filter",  "status:pending")
         self.t.config("report.annual.sort",    "due+")
 
+        this_year = time.gmtime(time.time())[0]
+        def jan1(year_offset):
+            return f"{this_year+year_offset}0101"
+
         # If a task is added with a due date ten years ago, with an annual recurrence,
         # then the synthetic tasks in between then and now have a due date that creeps.
         #
         # ID Due        Description
         # -- ---------- -----------
-        #  4 1/1/2002   foo
-        #  5 1/1/2003   foo
-        #  6 1/1/2004   foo
-        #  7 1/1/2005   foo
-        #  8 1/1/2006   foo
-        #  9 1/1/2007   foo
-        # 10 1/1/2008   foo
-        # 11 1/1/2009   foo
-        # 12 1/1/2010   foo
-        #  2 1/1/2000   foo
-        #  3 1/1/2001   foo
-
-        self.t("add foo due:20000101 recur:annual until:20150101")
+        #  4 1/1/2102   foo
+        #  5 1/1/2103   foo
+        #  6 1/1/2104   foo
+        #  7 1/1/2105   foo
+        #  8 1/1/2106   foo
+        #  9 1/1/2107   foo
+        # 10 1/1/2108   foo
+        # 11 1/1/2109   foo
+        # 12 1/1/2110   foo
+        #  2 1/1/2100   foo
+        #  3 1/1/2101   foo
+
+        self.t(f"add foo due:{jan1(1)} recur:annual until:{jan1(16)}")
         code, out, err = self.t("annual")
-        self.assertIn(" 2 20000101", out)
-        self.assertIn(" 3 20010101", out)
-        self.assertIn(" 4 20020101", out)
-        self.assertIn(" 5 20030101", out)
-        self.assertIn(" 6 20040101", out)
-        self.assertIn(" 7 20050101", out)
-        self.assertIn(" 8 20060101", out)
-        self.assertIn(" 9 20070101", out)
-        self.assertIn("10 20080101", out)
-        self.assertIn("11 20090101", out)
-        self.assertIn("12 20100101", out)
-        self.assertIn("13 20110101", out)
-        self.assertIn("14 20120101", out)
-        self.assertIn("15 20130101", out)
-        self.assertIn("16 20140101", out)
-        self.assertIn("17 20150101", out)
+        self.assertIn(f" 2 {jan1(1)}", out)
+        self.assertIn(f" 3 {jan1(2)}", out)
+        self.assertIn(f" 4 {jan1(3)}", out)
+        self.assertIn(f" 5 {jan1(4)}", out)
+        self.assertIn(f" 6 {jan1(5)}", out)
+        self.assertIn(f" 7 {jan1(6)}", out)
+        self.assertIn(f" 8 {jan1(7)}", out)
+        self.assertIn(f" 9 {jan1(8)}", out)
+        self.assertIn(f"10 {jan1(9)}", out)
+        self.assertIn(f"11 {jan1(10)}", out)
+        self.assertIn(f"12 {jan1(11)}", out)
+        self.assertIn(f"13 {jan1(12)}", out)
+        self.assertIn(f"14 {jan1(13)}", out)
+        self.assertIn(f"15 {jan1(14)}", out)
+        self.assertIn(f"16 {jan1(15)}", out)
+        self.assertIn(f"17 {jan1(16)}", out)
 
 
 # TODO Wait a recurring task