From 7014009a583d41f9d540b0be27554aa167914594 Mon Sep 17 00:00:00 2001
From: teauxfu <alex@southsun.tech>
Date: Sat, 24 Apr 2021 00:17:07 -0500
Subject: [PATCH 1/2] optionally allow empty/whitespace values

---
 tkcalendar/dateentry.py | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/tkcalendar/dateentry.py b/tkcalendar/dateentry.py
index e6d782e..bdbb9bd 100644
--- a/tkcalendar/dateentry.py
+++ b/tkcalendar/dateentry.py
@@ -81,7 +81,7 @@ class DateEntry(ttk.Entry):
                 'width': 12,
                 'xscrollcommand': ''}
 
-    def __init__(self, master=None, **kw):
+    def __init__(self, master=None, allow_empty=False, **kw):
         """
         Create an entry with a drop-down calendar to select a date.
 
@@ -143,6 +143,7 @@ def __init__(self, master=None, **kw):
         validatecmd = self.register(self._validate_date)
         self.configure(validate='focusout',
                        validatecommand=validatecmd)
+        self._allow_empty = allow_empty  # defaults to False
 
         # initially selected date
         self._date = self._calendar.selection_get()
@@ -155,7 +156,8 @@ def __init__(self, master=None, **kw):
                 self._date = self._calendar.date(year, month, day)
             except ValueError:
                 self._date = today
-        self._set_text(self.format_date(self._date))
+        if not self._allow_empty:
+            self._set_text(self.format_date(self._date))
 
         # --- bindings
         # reconfigure style if theme changed
@@ -288,8 +290,11 @@ def _validate_date(self):
             else:
                 return True
         except (ValueError, IndexError):
-            self._set_text(self.format_date(self._date))
-            return False
+            if self._allow_empty and self.get().strip() == '':
+                return True 
+            else:
+                self._set_text(self.format_date(self._date))
+                return False
 
     def _select(self, event=None):
         """Display the selected date in the entry and hide the calendar."""
@@ -328,7 +333,6 @@ def drop_down(self):
             self._top_cal.withdraw()
         else:
             self._validate_date()
-            date = self.parse_date(self.get())
             x = self.winfo_rootx()
             y = self.winfo_rooty() + self.winfo_height()
             if self.winfo_toplevel().attributes('-topmost'):
@@ -338,7 +342,9 @@ def drop_down(self):
             self._top_cal.geometry('+%i+%i' % (x, y))
             self._top_cal.deiconify()
             self._calendar.focus_set()
-            self._calendar.selection_set(date)
+            if self.get().strip() != '':
+                date = self.parse_date(self.get())
+                self._calendar.selection_set(date)
 
     def state(self, *args):
         """

From 8b8b0be2d0918609d92be89686664903ca3d06c5 Mon Sep 17 00:00:00 2001
From: teauxfu <alex@southsun.tech>
Date: Sat, 24 Apr 2021 21:30:01 -0500
Subject: [PATCH 2/2] add tests for widgets made with allow_empty=True

---
 tests/test_dateentry.py | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tests/test_dateentry.py b/tests/test_dateentry.py
index 52ac4db..0f2618d 100644
--- a/tests/test_dateentry.py
+++ b/tests/test_dateentry.py
@@ -165,3 +165,17 @@ def test_dateentry_functions(self):
         self.window.update()
         widget._select()
         self.assertIn('readonly', widget.state())
+        
+    def test_dateentry_allow_empty(self):
+        widget = DateEntry(self.window, allow_empty=True)
+        widget.pack()
+        self.window.update()
+
+        self.assertTrue(widget._allow_empty)
+        self.assertEqual(widget.get(), '')  # should start with no value
+        widget.focus_set()
+        self.window.focus_set()
+        self.assertEqual(widget.get(), '')  # should not populate with a value
+        
+        self.assertRaises(IndexError, widget.get_date)
+        self.assertRaises(ValueError, widget.set_date, '')