Handle errors in file I/O more gracefully

Show an error on I/O errors, permissions or Unicode decoding issues.

Open issue is that errors are not printed properly in the column UI.
Instead of calling CLIApplicationBase.error(), the column UI should
pass on the error to the user in a way that does not involve stderr.

topydo/lib/TodoFile.py

@@ -21,6 +21,9 @@ This module deals with todo.txt files.
 import codecs
 import os.path
 
+class TodoFileException(Exception):
+    pass
+
 
 class TodoFile(object):
     """
@@ -38,8 +41,9 @@ class TodoFile(object):
             todofile = codecs.open(self.path, 'r', encoding="utf-8")
             todos = todofile.readlines()
             todofile.close()
-        except IOError:
-            pass
+        except (PermissionError, IOError, UnicodeDecodeError) as err:
+            raise TodoFileException('Error while reading: {}'.format(str(err))) from err
+            todofile.close()
 
         return todos
 
@@ -51,14 +55,17 @@ class TodoFile(object):
         to the file.
         """
 
-        todofile = codecs.open(self.path, 'w', encoding="utf-8")
+        try:
+            todofile = codecs.open(self.path, 'w', encoding="utf-8")
 
-        if p_todos is list:
-            for todo in p_todos:
-                todofile.write(str(todo))
-        else:
-            todofile.write(p_todos)
+            if p_todos is list:
+                for todo in p_todos:
+                    todofile.write(str(todo))
+            else:
+                todofile.write(p_todos)
 
-        todofile.write("\n")
-
-        todofile.close()
+            todofile.write("\n")
+            todofile.close()
+        except (PermissionError, IOError) as err:
+            raise TodoFileException('Error while writing: {}'.format(str(err))) from err
+            todofile.close()

topydo/ui/CLIApplicationBase.py

@@ -23,6 +23,7 @@ import getopt
 import sys
 
 from topydo.lib.Color import AbstractColor, Color
+from topydo.lib.TodoFile import TodoFileException
 from topydo.lib.TopydoString import TopydoString
 
 MAIN_OPTS = "ac:C:d:ht:v"
@@ -157,7 +158,12 @@ def _retrieve_archive():
     and the second element is a TodoFile.
     """
     archive_file = TodoFile.TodoFile(config().archive())
-    archive = TodoListBase.TodoListBase(archive_file.read())
+
+    try:
+        archive = TodoListBase.TodoListBase(archive_file.read())
+    except TodoFileException as err:
+        error('Could not read archive file: {}.'.format(err))
+        archive = None
 
     return (archive, archive_file)
 
@@ -234,7 +240,10 @@ class CLIApplicationBase(object):
             command.execute()
 
             if archive.dirty:
-                archive_file.write(archive.print_todos())
+                try:
+                    archive_file.write(archive.print_todos())
+                except TodoFileException as err:
+                    error('Item(s) could not be archived: {}'.format(str(err)))
 
     def _help(self, args):
         if args is None:
@@ -298,8 +307,12 @@ class CLIApplicationBase(object):
             if self.backup:
                 self.backup.save(self.todolist)
 
-            self.todofile.write(self.todolist.print_todos())
-            self.todolist.dirty = False
+            try:
+                self.todofile.write(self.todolist.print_todos())
+                self.todolist.dirty = False
+            except TodoFileException as err:
+                error(str(err))
+                error('The last operation could not be saved.')
 
         self.backup = None
 

topydo/ui/cli/CLI.py

@@ -19,7 +19,7 @@
 import sys
 
 from topydo.ui.CLIApplicationBase import CLIApplicationBase, error
-from topydo.lib import TodoFile
+from topydo.lib.TodoFile import TodoFile, TodoFileException
 from topydo.lib.Config import config, ConfigError
 
 # First thing is to poke the configuration and check whether it's sane
@@ -32,7 +32,7 @@ except ConfigError as config_error:
     sys.exit(1)
 
 from topydo.Commands import get_subcommand
-from topydo.lib import TodoList
+from topydo.lib.TodoList import TodoList
 
 
 class CLIApplication(CLIApplicationBase):
@@ -47,8 +47,12 @@ class CLIApplication(CLIApplicationBase):
         """ Main entry function. """
         args = self._process_flags()
 
-        self.todofile = TodoFile.TodoFile(config().todotxt())
-        self.todolist = TodoList.TodoList(self.todofile.read())
+        self.todofile = TodoFile(config().todotxt())
+
+        try:
+            self.todolist = TodoList(self.todofile.read())
+        except TodoFileException as err:
+            error('Could not read todo file: {}'.format(str(err)))
 
         try:
             (subcommand, args) = get_subcommand(args)

topydo/ui/columns/Main.py

@@ -30,8 +30,9 @@ from topydo.lib.Sorter import Sorter
 from topydo.lib.Filter import get_filter_list, RelevanceFilter, DependencyFilter
 from topydo.lib.Utils import get_terminal_size
 from topydo.lib.View import View
+from topydo.lib.TodoFile import TodoFileException
 from topydo.lib.TodoFileWatched import TodoFileWatched
-from topydo.lib import TodoList
+from topydo.lib.TodoList import TodoList
 from topydo.ui.CLIApplicationBase import CLIApplicationBase, error, GENERIC_HELP
 from topydo.ui.columns.CommandLineWidget import CommandLineWidget
 from topydo.ui.columns.ConsoleWidget import ConsoleWidget
@@ -110,14 +111,26 @@ class UIApplication(CLIApplicationBase):
                 self.alt_layout_path = value
 
         def callback():
-            self.todolist.erase()
-            self.todolist.add_list(self.todofile.read())
-            self._update_all_columns()
-            self._redraw()
+            try:
+                todos = self.todofile.read()
+                self.todolist.erase()
+                self.todolist.add_list(todos)
+                self._update_all_columns()
+                self._redraw()
+            except TodoFileException as err:
+                self._print_to_console(
+                    'Error: Could not read todo file: {}'.format(err))
 
         self.column_width = config().column_width()
         self.todofile = TodoFileWatched(config().todotxt(), callback)
-        self.todolist = TodoList.TodoList(self.todofile.read())
+
+        try:
+            todos = self.todofile.read()
+        except TodoFileException as err:
+            error('Error: Could not read todo file: {}'.format(err))
+            sys.exit(1)
+
+        self.todolist = TodoList(todos)
 
         self.marked_todos = set()
 

topydo/ui/prompt/Prompt.py

@@ -20,6 +20,7 @@ import os.path
 import shlex
 import sys
 
+from topydo.lib.TodoFile import TodoFileException
 from topydo.ui.CLIApplicationBase import CLIApplicationBase, error, GENERIC_HELP
 from topydo.ui.prompt.TopydoCompleter import TopydoCompleter
 from prompt_toolkit.shortcuts import prompt
@@ -60,7 +61,12 @@ class PromptApplication(CLIApplicationBase):
         instance.
         """
         self.todolist.erase()
-        self.todolist.add_list(self.todofile.read())
+
+        try:
+            self.todolist.add_list(self.todofile.read())
+        except TodoFileException as err:
+            error('Could not read todo file: {}'.format(str(err)))
+
         self.completer = TopydoCompleter(self.todolist)
 
     def run(self):