Replace crashes with popups

src/TaskMachine/UI/Behaviors.hs

@@ -113,7 +113,7 @@ actionEditNew s = do
 actionEditSelected :: Action
 actionEditSelected s =
   case selectedTask (tasks s) of
-    Nothing -> error "no task selected" -- TODO: Add popup notification
+    Nothing -> pure s
     Just t  ->
       let edit = taskEdit RTaskEdit t ExistingTask
       in pure s{editor=Just edit}
@@ -194,7 +194,12 @@ actionFinishEdit t = pure . finishEdit t
 finishEdit :: TaskEdit RName -> UIState -> UIState
 finishEdit edit s =
   case editedTask edit of
-    Left e     -> error e -- TODO: Error popup
+    Left e     ->
+      let p = popup "Syntax error" e
+                [ ("Continue editing", B.continue)
+                , ("Abort", \s' -> B.continue s'{editor=Nothing})
+                ]
+      in  s{errorPopup=Just p}
     Right task -> s{tasks=modify task, editor=Nothing}
   where
     modify :: Task -> TaskList RName

todo.txt

@@ -1,4 +1,4 @@
-- c2018-09-18 Clean up file (adding creation/completion dates)
+x2018-10-23 c2018-09-18 Clean up file (adding creation/completion dates)
 - c2018-09-18 Purge - move completed tasks to a separate file
 x2018-10-23 c2018-09-28 Move cursor to beginning of task description when editing tasks
 - c2018-09-28 Syntax highlighting while editing tasks
@@ -9,4 +9,7 @@ x2018-09-30 c2018-09-18 Offer "retry" or "quit" +dialogue - couldn't load from t
 x2018-09-30 c2018-09-18 Offer "retry" or "quit" +dialogue - couldn't save to todo file
 x2018-09-30 c2018-09-18 Offer "retry" or "quit" +dialogue - syntax error in todo file
 x2018-09-30 c2018-09-30 Custom exception messages
-- c2018-10-23 Don't crash on parse errors etc.
+x2018-10-24 c2018-10-23 Don't crash on parse errors etc.
+- c2018-10-24 Add "u" - undo and "z" - redo buttons
+- c2018-10-24 Redo coloring - maybe black-on-white color scheme in-editor?
+- c2018-10-24 Reverse ordering of completed tasks - most recent at the top