X-Git-Url: https://git.madduck.net/etc/taskwarrior.git/blobdiff_plain/fdaab163072cb27edfef3bd00272449cfa618179..e9ee75194dcb6c60ff6b204f6b6ad135d4859628:/tasklib/task.py

diff --git a/tasklib/task.py b/tasklib/task.py
index e346f67..e8e5dfd 100644
--- a/tasklib/task.py
+++ b/tasklib/task.py
@@ -1,99 +1,655 @@
+from __future__ import print_function
 import copy
 import datetime
 import json
 import logging
 import os
+import pytz
+import six
+import sys
 import subprocess
+import tzlocal
 
 DATE_FORMAT = '%Y%m%dT%H%M%SZ'
 REPR_OUTPUT_SIZE = 10
 PENDING = 'pending'
 COMPLETED = 'completed'
 
+VERSION_2_1_0 = six.u('2.1.0')
+VERSION_2_2_0 = six.u('2.2.0')
+VERSION_2_3_0 = six.u('2.3.0')
+VERSION_2_4_0 = six.u('2.4.0')
+
 logger = logging.getLogger(__name__)
+local_zone = tzlocal.get_localzone()
 
 
 class TaskWarriorException(Exception):
     pass
 
 
-class Task(object):
+class ReadOnlyDictView(object):
+    """
+    Provides simplified read-only view upon dict object.
+    """
 
-    class DoesNotExist(Exception):
-        pass
+    def __init__(self, viewed_dict):
+        self.viewed_dict = viewed_dict
 
-    def __init__(self, warrior, data={}):
-        self.warrior = warrior
-        self._data = data
-        self._modified_fields = set()
+    def __getitem__(self, key):
+        return copy.deepcopy(self.viewed_dict.__getitem__(key))
 
-    def __unicode__(self):
-        return self['description']
+    def __contains__(self, k):
+        return self.viewed_dict.__contains__(k)
 
-    def __getitem__(self, key):
+    def __iter__(self):
+        for value in self.viewed_dict:
+            yield copy.deepcopy(value)
+
+    def __len__(self):
+        return len(self.viewed_dict)
+
+    def get(self, key, default=None):
+        return copy.deepcopy(self.viewed_dict.get(key, default))
+
+    def items(self):
+        return [copy.deepcopy(v) for v in self.viewed_dict.items()]
+
+    def values(self):
+        return [copy.deepcopy(v) for v in self.viewed_dict.values()]
+
+
+class SerializingObject(object):
+    """
+    Common ancestor for TaskResource & TaskFilter, since they both
+    need to serialize arguments.
+
+    Serializing method should hold the following contract:
+      - any empty value (meaning removal of the attribute)
+        is deserialized into a empty string
+      - None denotes a empty value for any attribute
+
+    Deserializing method should hold the following contract:
+      - None denotes a empty value for any attribute (however,
+        this is here as a safeguard, TaskWarrior currently does
+        not export empty-valued attributes) if the attribute
+        is not iterable (e.g. list or set), in which case
+        a empty iterable should be used.
+
+    Normalizing methods should hold the following contract:
+      - They are used to validate and normalize the user input.
+        Any attribute value that comes from the user (during Task
+        initialization, assignign values to Task attributes, or
+        filtering by user-provided values of attributes) is first
+        validated and normalized using the normalize_{key} method.
+      - If validation or normalization fails, normalizer is expected
+        to raise ValueError.
+    """
+
+    def _deserialize(self, key, value):
         hydrate_func = getattr(self, 'deserialize_{0}'.format(key),
-                               lambda x: x)
-        return hydrate_func(self._data.get(key))
+                               lambda x: x if x != '' else None)
+        return hydrate_func(value)
 
-    def __setitem__(self, key, value):
+    def _serialize(self, key, value):
         dehydrate_func = getattr(self, 'serialize_{0}'.format(key),
+                                 lambda x: x if x is not None else '')
+        return dehydrate_func(value)
+
+    def _normalize(self, key, value):
+        """
+        Use normalize_<key> methods to normalize user input. Any user
+        input will be normalized at the moment it is used as filter,
+        or entered as a value of Task attribute.
+        """
+
+        # None value should not be converted by normalizer
+        if value is None:
+            return None
+
+        normalize_func = getattr(self, 'normalize_{0}'.format(key),
                                  lambda x: x)
-        self._data[key] = dehydrate_func(value)
-        self._modified_fields.add(key)
 
-    def serialize_due(self, date):
+        return normalize_func(value)
+
+    def timestamp_serializer(self, date):
+        if not date:
+            return ''
+
+        # Any serialized timestamp should be localized, we need to
+        # convert to UTC before converting to string (DATE_FORMAT uses UTC)
+        date = date.astimezone(pytz.utc)
+
         return date.strftime(DATE_FORMAT)
 
-    def deserialize_due(self, date_str):
+    def timestamp_deserializer(self, date_str):
         if not date_str:
             return None
-        return datetime.datetime.strptime(date_str, DATE_FORMAT)
 
-    def serialize_annotations(self, annotations):
-        ann_list = list(annotations)
-        for ann in ann_list:
-            ann['entry'] = ann['entry'].strftime(DATE_FORMAT)
-        return ann_list
+        # Return timestamp localized in the local zone
+        naive_timestamp = datetime.datetime.strptime(date_str, DATE_FORMAT)
+        localized_timestamp = pytz.utc.localize(naive_timestamp)
+        return localized_timestamp.astimezone(local_zone)
 
-    def deserialize_annotations(self, annotations):
-        ann_list = list(annotations)
-        for ann in ann_list:
-            ann['entry'] = datetime.datetime.strptime(
-                ann['entry'], DATE_FORMAT)
-        return ann_list
+    def serialize_entry(self, value):
+        return self.timestamp_serializer(value)
 
-    def deserialize_tags(self, tags):
-        if isinstance(tags, basestring):
-            return tags.split(',') if tags else []
-        return tags
+    def deserialize_entry(self, value):
+        return self.timestamp_deserializer(value)
+
+    def normalize_entry(self, value):
+        return self.datetime_normalizer(value)
+
+    def serialize_modified(self, value):
+        return self.timestamp_serializer(value)
+
+    def deserialize_modified(self, value):
+        return self.timestamp_deserializer(value)
+
+    def normalize_modified(self, value):
+        return self.datetime_normalizer(value)
+
+    def serialize_due(self, value):
+        return self.timestamp_serializer(value)
+
+    def deserialize_due(self, value):
+        return self.timestamp_deserializer(value)
+
+    def normalize_due(self, value):
+        return self.datetime_normalizer(value)
+
+    def serialize_scheduled(self, value):
+        return self.timestamp_serializer(value)
+
+    def deserialize_scheduled(self, value):
+        return self.timestamp_deserializer(value)
+
+    def normalize_scheduled(self, value):
+        return self.datetime_normalizer(value)
+
+    def serialize_until(self, value):
+        return self.timestamp_serializer(value)
+
+    def deserialize_until(self, value):
+        return self.timestamp_deserializer(value)
+
+    def normalize_until(self, value):
+        return self.datetime_normalizer(value)
+
+    def serialize_wait(self, value):
+        return self.timestamp_serializer(value)
+
+    def deserialize_wait(self, value):
+        return self.timestamp_deserializer(value)
+
+    def normalize_wait(self, value):
+        return self.datetime_normalizer(value)
+
+    def serialize_annotations(self, value):
+        value = value if value is not None else []
+
+        # This may seem weird, but it's correct, we want to export
+        # a list of dicts as serialized value
+        serialized_annotations = [json.loads(annotation.export_data())
+                                  for annotation in value]
+        return serialized_annotations if serialized_annotations else ''
+
+    def deserialize_annotations(self, data):
+        return [TaskAnnotation(self, d) for d in data] if data else []
 
     def serialize_tags(self, tags):
         return ','.join(tags) if tags else ''
 
+    def deserialize_tags(self, tags):
+        if isinstance(tags, six.string_types):
+            return tags.split(',') if tags else []
+        return tags or []
+
+    def serialize_depends(self, value):
+        # Return the list of uuids
+        value = value if value is not None else set()
+        return ','.join(task['uuid'] for task in value)
+
+    def deserialize_depends(self, raw_uuids):
+        raw_uuids = raw_uuids or ''  # Convert None to empty string
+        uuids = raw_uuids.split(',')
+        return set(self.warrior.tasks.get(uuid=uuid) for uuid in uuids if uuid)
+
+    def datetime_normalizer(self, value):
+        """
+        Normalizes date/datetime value (considered to come from user input)
+        to localized datetime value. Following conversions happen:
+
+        naive date -> localized datetime with the same date, and time=midnight
+        naive datetime -> localized datetime with the same value
+        localized datetime -> localized datetime (no conversion)
+        """
+
+        if (isinstance(value, datetime.date)
+            and not isinstance(value, datetime.datetime)):
+            # Convert to local midnight
+            value_full = datetime.datetime.combine(value, datetime.time.min)
+            localized = local_zone.localize(value_full)
+        elif isinstance(value, datetime.datetime) and value.tzinfo is None:
+            # Convert to localized datetime object
+            localized = local_zone.localize(value)
+        else:
+            # If the value is already localized, there is no need to change
+            # time zone at this point. Also None is a valid value too.
+            localized = value
+
+        return localized
+
+    def normalize_uuid(self, value):
+        # Enforce sane UUID
+        if not isinstance(value, six.string_types) or value == '':
+            raise ValueError("UUID must be a valid non-empty string, "
+                             "not: {}".format(value))
+
+        return value
+
+
+class TaskResource(SerializingObject):
+    read_only_fields = []
+
+    def _load_data(self, data):
+        self._data = dict((key, self._deserialize(key, value))
+                          for key, value in data.items())
+        # We need to use a copy for original data, so that changes
+        # are not propagated.
+        self._original_data = copy.deepcopy(self._data)
+
+    def _update_data(self, data, update_original=False):
+        """
+        Low level update of the internal _data dict. Data which are coming as
+        updates should already be serialized. If update_original is True, the
+        original_data dict is updated as well.
+        """
+        self._data.update(dict((key, self._deserialize(key, value))
+                               for key, value in data.items()))
+
+        if update_original:
+            self._original_data = copy.deepcopy(self._data)
+
+
+    def __getitem__(self, key):
+        # This is a workaround to make TaskResource non-iterable
+        # over simple index-based iteration
+        try:
+            int(key)
+            raise StopIteration
+        except ValueError:
+            pass
+
+        if key not in self._data:
+            self._data[key] = self._deserialize(key, None)
+
+        return self._data.get(key)
+
+    def __setitem__(self, key, value):
+        if key in self.read_only_fields:
+            raise RuntimeError('Field \'%s\' is read-only' % key)
+
+        # Normalize the user input before saving it
+        value = self._normalize(key, value)
+        self._data[key] = value
+
+    def __str__(self):
+        s = six.text_type(self.__unicode__())
+        if not six.PY3:
+            s = s.encode('utf-8')
+        return s
+
+    def __repr__(self):
+        return str(self)
+
+    def export_data(self):
+        """
+        Exports current data contained in the Task as JSON
+        """
+
+        # We need to remove spaces for TW-1504, use custom separators
+        data_tuples = ((key, self._serialize(key, value))
+                       for key, value in six.iteritems(self._data))
+
+        # Empty string denotes empty serialized value, we do not want
+        # to pass that to TaskWarrior.
+        data_tuples = filter(lambda t: t[1] is not '', data_tuples)
+        data = dict(data_tuples)
+        return json.dumps(data, separators=(',',':'))
+
+    @property
+    def _modified_fields(self):
+        writable_fields = set(self._data.keys()) - set(self.read_only_fields)
+        for key in writable_fields:
+            new_value = self._data.get(key)
+            old_value = self._original_data.get(key)
+
+            # Make sure not to mark data removal as modified field if the
+            # field originally had some empty value
+            if key in self._data and not new_value and not old_value:
+                continue
+
+            if new_value != old_value:
+                yield key
+
+    @property
+    def modified(self):
+        return bool(list(self._modified_fields))
+
+
+class TaskAnnotation(TaskResource):
+    read_only_fields = ['entry', 'description']
+
+    def __init__(self, task, data={}):
+        self.task = task
+        self._load_data(data)
+
+    def remove(self):
+        self.task.remove_annotation(self)
+
+    def __unicode__(self):
+        return self['description']
+
+    def __eq__(self, other):
+        # consider 2 annotations equal if they belong to the same task, and
+        # their data dics are the same
+        return self.task == other.task and self._data == other._data
+
+    __repr__ = __unicode__
+
+
+class Task(TaskResource):
+    read_only_fields = ['id', 'entry', 'urgency', 'uuid', 'modified']
+
+    class DoesNotExist(Exception):
+        pass
+
+    class CompletedTask(Exception):
+        """
+        Raised when the operation cannot be performed on the completed task.
+        """
+        pass
+
+    class DeletedTask(Exception):
+        """
+        Raised when the operation cannot be performed on the deleted task.
+        """
+        pass
+
+    class NotSaved(Exception):
+        """
+        Raised when the operation cannot be performed on the task, because
+        it has not been saved to TaskWarrior yet.
+        """
+        pass
+
+    @classmethod
+    def from_input(cls, input_file=sys.stdin, modify=None, warrior=None):
+        """
+        Creates a Task object, directly from the stdin, by reading one line.
+        If modify=True, two lines are used, first line interpreted as the
+        original state of the Task object, and second line as its new,
+        modified value. This is consistent with the TaskWarrior's hook
+        system.
+
+        Object created by this method should not be saved, deleted
+        or refreshed, as t could create a infinite loop. For this
+        reason, TaskWarrior instance is set to None.
+
+        Input_file argument can be used to specify the input file,
+        but defaults to sys.stdin.
+        """
+
+        # Detect the hook type if not given directly
+        name = os.path.basename(sys.argv[0])
+        modify = name.startswith('on-modify') if modify is None else modify
+
+        # Create the TaskWarrior instance if none passed
+        if warrior is None:
+            hook_parent_dir = os.path.dirname(os.path.dirname(sys.argv[0]))
+            warrior = TaskWarrior(data_location=hook_parent_dir)
+
+        # TaskWarrior instance is set to None
+        task = cls(warrior)
+
+        # Load the data from the input
+        task._load_data(json.loads(input_file.readline().strip()))
+
+        # If this is a on-modify event, we are provided with additional
+        # line of input, which provides updated data
+        if modify:
+            task._update_data(json.loads(input_file.readline().strip()))
+
+        return task
+
+    def __init__(self, warrior, **kwargs):
+        self.warrior = warrior
+
+        # Check that user is not able to set read-only value in __init__
+        for key in kwargs.keys():
+            if key in self.read_only_fields:
+                raise RuntimeError('Field \'%s\' is read-only' % key)
+
+        # We serialize the data in kwargs so that users of the library
+        # do not have to pass different data formats via __setitem__ and
+        # __init__ methods, that would be confusing
+
+        # Rather unfortunate syntax due to python2.6 comaptiblity
+        self._data = dict((key, self._normalize(key, value))
+                          for (key, value) in six.iteritems(kwargs))
+        self._original_data = copy.deepcopy(self._data)
+
+        # Provide read only access to the original data
+        self.original = ReadOnlyDictView(self._original_data)
+
+    def __unicode__(self):
+        return self['description']
+
+    def __eq__(self, other):
+        if self['uuid'] and other['uuid']:
+            # For saved Tasks, just define equality by equality of uuids
+            return self['uuid'] == other['uuid']
+        else:
+            # If the tasks are not saved, compare the actual instances
+            return id(self) == id(other)
+
+
+    def __hash__(self):
+        if self['uuid']:
+            # For saved Tasks, just define equality by equality of uuids
+            return self['uuid'].__hash__()
+        else:
+            # If the tasks are not saved, return hash of instance id
+            return id(self).__hash__()
+
+    @property
+    def completed(self):
+        return self['status'] == six.text_type('completed')
+
+    @property
+    def deleted(self):
+        return self['status'] == six.text_type('deleted')
+
+    @property
+    def waiting(self):
+        return self['status'] == six.text_type('waiting')
+
+    @property
+    def pending(self):
+        return self['status'] == six.text_type('pending')
+
+    @property
+    def saved(self):
+        return self['uuid'] is not None or self['id'] is not None
+
+    def serialize_depends(self, cur_dependencies):
+        # Check that all the tasks are saved
+        for task in (cur_dependencies or set()):
+            if not task.saved:
+                raise Task.NotSaved('Task \'%s\' needs to be saved before '
+                                    'it can be set as dependency.' % task)
+
+        return super(Task, self).serialize_depends(cur_dependencies)
+
+    def format_depends(self):
+        # We need to generate added and removed dependencies list,
+        # since Taskwarrior does not accept redefining dependencies.
+
+        # This cannot be part of serialize_depends, since we need
+        # to keep a list of all depedencies in the _data dictionary,
+        # not just currently added/removed ones
+
+        old_dependencies = self._original_data.get('depends', set())
+
+        added = self['depends'] - old_dependencies
+        removed = old_dependencies - self['depends']
+
+        # Removed dependencies need to be prefixed with '-'
+        return 'depends:' + ','.join(
+                [t['uuid'] for t in added] +
+                ['-' + t['uuid'] for t in removed]
+            )
+
+    def format_description(self):
+        # Task version older than 2.4.0 ignores first word of the
+        # task description if description: prefix is used
+        if self.warrior.version < VERSION_2_4_0:
+            return self._data['description']
+        else:
+            return "description:'{0}'".format(self._data['description'] or '')
+
     def delete(self):
-        self.warrior.execute_command([self['id'], 'delete'], config_override={
-            'confirmation': 'no',
-        })
+        if not self.saved:
+            raise Task.NotSaved("Task needs to be saved before it can be deleted")
+
+        # Refresh the status, and raise exception if the task is deleted
+        self.refresh(only_fields=['status'])
+
+        if self.deleted:
+            raise Task.DeletedTask("Task was already deleted")
+
+        self.warrior.execute_command([self['uuid'], 'delete'])
+
+        # Refresh the status again, so that we have updated info stored
+        self.refresh(only_fields=['status'])
+
 
     def done(self):
-        self.warrior.execute_command([self['id'], 'done'])
+        if not self.saved:
+            raise Task.NotSaved("Task needs to be saved before it can be completed")
+
+        # Refresh, and raise exception if task is already completed/deleted
+        self.refresh(only_fields=['status'])
+
+        if self.completed:
+            raise Task.CompletedTask("Cannot complete a completed task")
+        elif self.deleted:
+            raise Task.DeletedTask("Deleted task cannot be completed")
+
+        self.warrior.execute_command([self['uuid'], 'done'])
+
+        # Refresh the status again, so that we have updated info stored
+        self.refresh(only_fields=['status'])
 
     def save(self):
-        args = [self['id'], 'modify'] if self['id'] else ['add']
+        if self.saved and not self.modified:
+            return
+
+        args = [self['uuid'], 'modify'] if self.saved else ['add']
         args.extend(self._get_modified_fields_as_args())
+        output = self.warrior.execute_command(args)
+
+        # Parse out the new ID, if the task is being added for the first time
+        if not self.saved:
+            id_lines = [l for l in output if l.startswith('Created task ')]
+
+            # Complain loudly if it seems that more tasks were created
+            # Should not happen
+            if len(id_lines) != 1 or len(id_lines[0].split(' ')) != 3:
+                raise TaskWarriorException("Unexpected output when creating "
+                                           "task: %s" % '\n'.join(id_lines))
+
+            # Circumvent the ID storage, since ID is considered read-only
+            self._data['id'] = int(id_lines[0].split(' ')[2].rstrip('.'))
+
+        # Refreshing is very important here, as not only modification time
+        # is updated, but arbitrary attribute may have changed due hooks
+        # altering the data before saving
+        self.refresh()
+
+    def add_annotation(self, annotation):
+        if not self.saved:
+            raise Task.NotSaved("Task needs to be saved to add annotation")
+
+        args = [self['uuid'], 'annotate', annotation]
         self.warrior.execute_command(args)
-        self._modified_fields.clear()
+        self.refresh(only_fields=['annotations'])
+
+    def remove_annotation(self, annotation):
+        if not self.saved:
+            raise Task.NotSaved("Task needs to be saved to remove annotation")
+
+        if isinstance(annotation, TaskAnnotation):
+            annotation = annotation['description']
+        args = [self['uuid'], 'denotate', annotation]
+        self.warrior.execute_command(args)
+        self.refresh(only_fields=['annotations'])
 
     def _get_modified_fields_as_args(self):
         args = []
-        for field in self._modified_fields:
-            args.append('{}:{}'.format(field, self._data[field]))
-        return args
 
-    __repr__ = __unicode__
+        def add_field(field):
+            # Add the output of format_field method to args list (defaults to
+            # field:value)
+            serialized_value = self._serialize(field, self._data[field])
+
+            # Empty values should not be enclosed in quotation marks, see
+            # TW-1510
+            if serialized_value is '':
+                escaped_serialized_value = ''
+            else:
+                escaped_serialized_value = "'{0}'".format(serialized_value)
+
+            format_default = lambda: "{0}:{1}".format(field,
+                                                      escaped_serialized_value)
+
+            format_func = getattr(self, 'format_{0}'.format(field),
+                                  format_default)
 
+            args.append(format_func())
+
+        # If we're modifying saved task, simply pass on all modified fields
+        if self.saved:
+            for field in self._modified_fields:
+                add_field(field)
+        # For new tasks, pass all fields that make sense
+        else:
+            for field in self._data.keys():
+                if field in self.read_only_fields:
+                    continue
+                add_field(field)
+
+        return args
 
-class TaskFilter(object):
+    def refresh(self, only_fields=[]):
+        # Raise error when trying to refresh a task that has not been saved
+        if not self.saved:
+            raise Task.NotSaved("Task needs to be saved to be refreshed")
+
+        # We need to use ID as backup for uuid here for the refreshes
+        # of newly saved tasks. Any other place in the code is fine
+        # with using UUID only.
+        args = [self['uuid'] or self['id'], 'export']
+        new_data = json.loads(self.warrior.execute_command(args)[0])
+        if only_fields:
+            to_update = dict(
+                [(k, new_data.get(k)) for k in only_fields])
+            self._update_data(to_update, update_original=True)
+        else:
+            self._load_data(new_data)
+
+class TaskFilter(SerializingObject):
     """
     A set of parameters to filter the task list with.
     """
@@ -106,7 +662,29 @@ class TaskFilter(object):
 
     def add_filter_param(self, key, value):
         key = key.replace('__', '.')
-        self.filter_params.append('{0}:{1}'.format(key, value))
+
+        # Replace the value with empty string, since that is the
+        # convention in TW for empty values
+        attribute_key = key.split('.')[0]
+
+        # Since this is user input, we need to normalize before we serialize
+        value = self._normalize(key, value)
+        value = self._serialize(attribute_key, value)
+
+        # If we are filtering by uuid:, do not use uuid keyword
+        # due to TW-1452 bug
+        if key == 'uuid':
+            self.filter_params.insert(0, value)
+        else:
+            # Surround value with aphostrophes unless it's a empty string
+            value = "'%s'" % value if value else ''
+
+            # We enforce equality match by using 'is' (or 'none') modifier
+            # Without using this syntax, filter fails due to TW-1479
+            modifier = '.is' if value else '.none'
+            key = key + modifier if '.' not in key else key
+
+            self.filter_params.append("{0}:{1}".format(key, value))
 
     def get_filter_params(self):
         return [f for f in self.filter_params if f]
@@ -230,12 +808,16 @@ class TaskQuerySet(object):
 class TaskWarrior(object):
     def __init__(self, data_location='~/.task', create=True):
         data_location = os.path.expanduser(data_location)
-        if not os.path.exists(data_location):
+        if create and not os.path.exists(data_location):
             os.makedirs(data_location)
         self.config = {
             'data.location': os.path.expanduser(data_location),
+            'confirmation': 'no',
+            'dependency.confirmation': 'no',  # See TW-1483 or taskrc man page
+            'recurrence.confirmation': 'no',  # Necessary for modifying R tasks
         }
         self.tasks = TaskQuerySet(self)
+        self.version = self._get_version()
 
     def _get_command_args(self, args, config_override={}):
         command_args = ['task', 'rc:/']
@@ -246,24 +828,49 @@ class TaskWarrior(object):
         command_args.extend(map(str, args))
         return command_args
 
-    def execute_command(self, args, config_override={}):
+    def _get_version(self):
+        p = subprocess.Popen(
+                ['task', '--version'],
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE)
+        stdout, stderr = [x.decode('utf-8') for x in p.communicate()]
+        return stdout.strip('\n')
+
+    def execute_command(self, args, config_override={}, allow_failure=True):
         command_args = self._get_command_args(
             args, config_override=config_override)
         logger.debug(' '.join(command_args))
         p = subprocess.Popen(command_args, stdout=subprocess.PIPE,
                              stderr=subprocess.PIPE)
-        stdout, stderr = p.communicate()
-        if p.returncode:
-            error_msg = stderr.strip().splitlines()[-1]
+        stdout, stderr = [x.decode('utf-8') for x in p.communicate()]
+        if p.returncode and allow_failure:
+            if stderr.strip():
+                error_msg = stderr.strip()
+            else:
+                error_msg = stdout.strip()
             raise TaskWarriorException(error_msg)
         return stdout.strip().split('\n')
 
+    def enforce_recurrence(self):
+        # Run arbitrary report command which will trigger generation
+        # of recurrent tasks.
+        # TODO: Make a version dependant enforcement once
+        #       TW-1531 is handled
+        self.execute_command(['next'], allow_failure=False)
+
     def filter_tasks(self, filter_obj):
+        self.enforce_recurrence()
         args = ['export', '--'] + filter_obj.get_filter_params()
         tasks = []
         for line in self.execute_command(args):
             if line:
-                tasks.append(Task(self, json.loads(line.strip(','))))
+                data = line.strip(',')
+                try:
+                    filtered_task = Task(self)
+                    filtered_task._load_data(json.loads(data))
+                    tasks.append(filtered_task)
+                except ValueError:
+                    raise TaskWarriorException('Invalid JSON: %s' % data)
         return tasks
 
     def merge_with(self, path, push=False):
@@ -273,6 +880,4 @@ class TaskWarrior(object):
         })
 
     def undo(self):
-        self.execute_command(['undo'], config_override={
-            'confirmation': 'no',
-        })
+        self.execute_command(['undo'])