save in-progress replies via persisting SourceConversationWrapper

securedrop_client/gui/widgets.py

@@ -22,7 +22,7 @@
 import sys
 
 from gettext import gettext as _
-from typing import List
+from typing import Dict, List  # noqa: F401
 from uuid import uuid4
 from PyQt5.QtCore import Qt, pyqtSlot, pyqtSignal, QTimer, QSize, pyqtBoundSignal, QObject
 from PyQt5.QtGui import QIcon, QPalette, QBrush, QColor, QFont, QLinearGradient
@@ -609,6 +609,8 @@ def __init__(self, parent: QObject):
         self.layout.addWidget(self.source_list)
         self.layout.addWidget(self.view_holder)
 
+        self.source_conversations = {}  # type: Dict[Source, SourceConversationWrapper]
+
     def setup(self, controller):
         """
         Pass through the controller object to this widget.
@@ -631,7 +633,14 @@ def on_source_changed(self):
         source = self.source_list.get_current_source()
 
         if source:
-            conversation_wrapper = SourceConversationWrapper(source, self.controller)
+            # Try to get the SourceConversationWrapper from the persistent dict,
+            # else we create it.
+            try:
+                conversation_wrapper = self.source_conversations[source]
+            except KeyError:
+                conversation_wrapper = SourceConversationWrapper(source, self.controller)
+                self.source_conversations[source] = conversation_wrapper
+
             self.set_conversation(conversation_wrapper)
         else:
             self.clear_conversation()

tests/gui/test_widgets.py

@@ -470,6 +470,55 @@ def test_MainView_on_source_changed_updates_conversation_view(mocker, session):
     assert add_file_fn.call_count == 1
 
 
+def test_MainView_on_source_changed_SourceConversationWrapper_is_preserved(mocker, session):
+    """
+    SourceConversationWrapper contains ReplyBoxWidget - this tests that we do not recreate
+    SourceConversationWrapper when we click away from a given source. We should create it the
+    first time, and then it should persist.
+    """
+    mv = MainView(None)
+    mv.source_list = mocker.MagicMock()
+    mv.set_conversation = mocker.MagicMock()
+    mv.controller = mocker.MagicMock(is_authenticated=True)
+    source = factory.Source()
+    source2 = factory.Source()
+    session.add(source)
+    session.add(source2)
+    session.commit()
+
+    source_conversation_init = mocker.patch(
+        'securedrop_client.gui.widgets.SourceConversationWrapper.__init__', return_value=None)
+
+    # We expect on the first call, SourceConversationWrapper.__init__ should be called.
+    mv.source_list.get_current_source = mocker.MagicMock(return_value=source)
+    mv.on_source_changed()
+    assert mv.set_conversation.call_count == 1
+    assert source_conversation_init.call_count == 1
+
+    # Reset mock call counts for next call of on_source_changed.
+    source_conversation_init.reset_mock()
+    mv.set_conversation.reset_mock()
+
+    # Now click on another source (source2). Since this is the first time we have clicked
+    # on source2, we expect on the first call, SourceConversationWrapper.__init__ should be
+    # called.
+    mv.source_list.get_current_source = mocker.MagicMock(return_value=source2)
+    mv.on_source_changed()
+    assert mv.set_conversation.call_count == 1
+    assert source_conversation_init.call_count == 1
+
+    # Reset mock call counts for next call of on_source_changed.
+    source_conversation_init.reset_mock()
+    mv.set_conversation.reset_mock()
+
+    # But if we click back (call on_source_changed again) to the source,
+    # its SourceConversationWrapper should _not_ be recreated.
+    mv.source_list.get_current_source = mocker.MagicMock(return_value=source)
+    mv.on_source_changed()
+    assert mv.set_conversation.call_count == 1
+    assert source_conversation_init.call_count == 0
+
+
 def test_MainView_set_conversation(mocker):
     """
     Ensure the passed-in widget is added to the layout of the main view holder