From 5fd17ed2104d644adbc6cb779c879773751999e1 Mon Sep 17 00:00:00 2001
From: Chris <audionautic@gmail.com>
Date: Fri, 3 Jul 2020 10:50:57 -0700
Subject: [PATCH] closes #593 & #591 - dynamic updates causes slowdowns and
 loses selection

---
 gooey/gui/components/widgets/dropdown.py | 28 ++++++++++---
 gooey/tests/test_dropdown.py             | 52 ++++++++++++++++++++++++
 2 files changed, 74 insertions(+), 6 deletions(-)
 create mode 100644 gooey/tests/test_dropdown.py

diff --git a/gooey/gui/components/widgets/dropdown.py b/gooey/gui/components/widgets/dropdown.py
index f89d6c7..5511aaa 100644
--- a/gooey/gui/components/widgets/dropdown.py
+++ b/gooey/gui/components/widgets/dropdown.py
@@ -1,3 +1,5 @@
+from contextlib import contextmanager
+
 from gooey.gui.components.widgets.bases import TextContainer
 import wx
 
@@ -18,12 +20,9 @@ class Dropdown(TextContainer):
             style=wx.CB_DROPDOWN)
 
     def setOptions(self, options):
-        prevSelection = self.widget.GetSelection()
-        self.widget.Clear()
-        for option in [_('select_option')] + options:
-            self.widget.Append(option)
-        self.widget.SetSelection(0)
-
+        with self.retainSelection():
+            self.widget.Clear()
+            self.widget.SetItems([_('select_option')] + options)
 
     def setValue(self, value):
         ## +1 to offset the default placeholder value
@@ -40,3 +39,20 @@ class Dropdown(TextContainer):
 
     def formatOutput(self, metadata, value):
         return formatters.dropdown(metadata, value)
+
+    @contextmanager
+    def retainSelection(self):
+        """"
+        Retains the selected dropdown option (when possible)
+        across mutations due to dynamic updates.
+        """
+        prevSelection = self.widget.GetSelection()
+        prevValue = self.widget.GetValue()
+        try:
+            yield
+        finally:
+            current_at_index = self.widget.GetString(prevSelection)
+            if prevValue == current_at_index:
+                self.widget.SetSelection(prevSelection)
+            else:
+                self.widget.SetSelection(0)
diff --git a/gooey/tests/test_dropdown.py b/gooey/tests/test_dropdown.py
new file mode 100644
index 0000000..97d5f43
--- /dev/null
+++ b/gooey/tests/test_dropdown.py
@@ -0,0 +1,52 @@
+import unittest
+from argparse import ArgumentParser
+from unittest.mock import patch
+
+from tests.harness import instrumentGooey
+
+
+class TestGooeyDropdown(unittest.TestCase):
+
+    def make_parser(self, **kwargs):
+        parser = ArgumentParser(description='description')
+        parser.add_argument('--dropdown', **kwargs)
+        return parser
+
+
+    @patch("gui.containers.application.seeder.fetchDynamicProperties")
+    def test_dropdown_behavior(self, mock):
+        """
+        Testing that:
+            - default values are used as the initial selection (when present)
+            - Initial selection defaults to placeholder when no defaults supplied
+            - selection is preserved (when possible) across dynamic updates
+        """
+        testcases = [
+            # tuples of [choices, default, initalSelection, dynamicUpdate, expectedFinalSelection]
+            [['1', '2'], None, 'Select Option', ['1', '2','3'], 'Select Option'],
+            [['1', '2'], '2', '2', ['1', '2','3'],  '2'],
+            [['1', '2'], '1', '1', ['1', '2','3'], '1'],
+            # dynamic updates removed our selected value; defaults back to placeholder
+            [['1', '2'], '2', '2', ['1', '3'], 'Select Option'],
+        ]
+
+        for choices, default, initalSelection, dynamicUpdate, expectedFinalSelection in testcases:
+            parser = self.make_parser(choices=choices, default=default)
+            with instrumentGooey(parser) as (app, gooeyApp):
+                dropdown = gooeyApp.configs[0].reifiedWidgets[0]
+                # ensure that default values (when supplied) are selected in the UI
+                self.assertEqual(dropdown.widget.GetValue(), initalSelection)
+                # fire a dynamic update with the mock values
+                mock.return_value = {'--dropdown': dynamicUpdate}
+                gooeyApp.fetchExternalUpdates()
+                # the values in the UI now reflect those returned from the update
+                # note: we're appending the ['select option'] bit here as it gets automatically added
+                # in the UI.
+                expectedValues = ['Select Option'] + dynamicUpdate
+                self.assertEqual(dropdown.widget.GetItems(), expectedValues)
+                # and our selection is what we expect
+                self.assertEqual(dropdown.widget.GetValue(), expectedFinalSelection)
+
+
+if __name__ == '__main__':
+    unittest.main()
\ No newline at end of file