WIP: Stop using arrow/dateutil in favor of standard library

The standard library's date formatting is better now (zoneinfo was added
in 3.9), so we don't need to rely on the arrow and dateutil libraries.

A few specifics:
* for the last sync file, just store a timestamp in ISO format. No back-
  compat is needed since reading is already fallible.
* the API's date format is fixed, so tweak it into ISO format and parse.
* to replace arrow's humanize, we can use babel's format_timedelta.

Note that this only actually removes arrow from our dependency tree as
dateutil is a dependency of alembic. It's already been removed upstream,
so once we upgrade alembic/SQLalchemy, it'll go away too.

client/build-requirements.txt

@@ -1,5 +1,4 @@
 alembic==1.1.0 --hash=sha256:de24f96f0ee198d4ebde1360e81d2590fa46ca3971f73e25a18b516917e8e178
-arrow==0.12.1 --hash=sha256:1ebe2f35dc36d7150c00fa310d3a7e71616b48f2b0b522ad76b518fb5668174c
 jinja2==3.1.3 --hash=sha256:a987f55fbbaebab55d75cf41ae415808855a40cf9d72ebf2dbe2aa00fd9243eb
 mako==1.2.2 --hash=sha256:a891058241a8c119dfdb8c1e884d97910365bff24a364be850dbd0eb0248d0fa
 markupsafe==2.0.1 --hash=sha256:465ea64f8d1af7349736132ab0f5521483551ae8814c0e655fca81f9b7c3f0ec --hash=sha256:9a055a175f351a559937fb80ebb2885d005283577a016c0139817e261fb759eb

client/pyproject.toml

@@ -11,8 +11,6 @@ python = "^3.11"
 Jinja2 = "3.1.3"
 SQLAlchemy = "^1.3.3"
 alembic = "^1.1.0"
-arrow = "^0.12.1"
-python-dateutil = "^2.7.5"
 
 [tool.poetry.group.dev.dependencies]
 # In production these two are installed using a system package
@@ -39,6 +37,5 @@ pytest-random-order = "*"
 semgrep = "*"
 translate-toolkit = "*"
 types-polib = "*"
-types-python-dateutil = "*"
 types-setuptools = "^73.0.0"
 vcrpy = "^6.0.1"

client/securedrop_client/gui/datetime_helpers.py

@@ -4,29 +4,41 @@
 """
 
 import datetime
+from zoneinfo import ZoneInfo
 
-import arrow
-from dateutil import tz
+from babel.dates import format_timedelta
 from PyQt5.QtCore import QTimeZone
 
 
 def format_datetime_month_day(date: datetime.datetime) -> str:
     """
     Formats date as e.g. Sep 16
     """
-    return arrow.get(date).format("MMM D")
+    return date.strftime("%b %-d")
 
 
 def localise_datetime(date: datetime.datetime) -> datetime.datetime:
     """
     Localise the datetime object to system timezone
     """
     local_timezone = QTimeZone.systemTimeZoneId().data().decode("utf-8")
-    return arrow.get(date).to(tz.gettz(local_timezone)).datetime
+    return date.replace(tzinfo=datetime.UTC).astimezone(ZoneInfo(local_timezone))
 
 
 def format_datetime_local(date: datetime.datetime) -> str:
     """
     Localise date and return as a string in the format e.g. Sep 16
     """
     return format_datetime_month_day(localise_datetime(date))
+
+
+def format_relative_time(dt: datetime.datetime) -> str:
+    """
+    Returns a human-readable string representing the time difference
+    between the given datetime and now.
+    """
+    now = datetime.datetime.now(datetime.UTC)
+    if dt.tzinfo is None:
+        dt = dt.replace(tzinfo=datetime.UTC)
+
+    return format_timedelta(now - dt)

client/securedrop_client/gui/main.py

@@ -19,6 +19,7 @@
 """
 
 import logging
+from datetime import datetime
 from gettext import gettext as _
 
 from PyQt5.QtCore import Qt
@@ -28,6 +29,7 @@
 from securedrop_client import __version__, state
 from securedrop_client.db import Source, User
 from securedrop_client.gui.auth import LoginDialog
+from securedrop_client.gui.datetime_helpers import format_relative_time
 from securedrop_client.gui.widgets import BottomPane, LeftPane, MainView
 from securedrop_client.logic import Controller
 from securedrop_client.resources import load_all_fonts, load_css, load_icon
@@ -168,12 +170,12 @@ def show_sources(self, sources: list[Source]) -> None:
         """
         self.main_view.show_sources(sources)
 
-    def show_last_sync(self, updated_on):  # type: ignore[no-untyped-def]
+    def show_last_sync(self, updated_on: datetime) -> None:
         """
         Display a message indicating the time of last sync with the server.
         """
         if updated_on:
-            self.update_sync_status(_("Last Refresh: {}").format(updated_on.humanize()))
+            self.update_sync_status(_("Last Refresh: {}").format(format_relative_time(updated_on)))
         else:
             self.update_sync_status(_("Last Refresh: never"))
 

client/securedrop_client/gui/widgets.py

@@ -26,7 +26,6 @@
 from typing import Optional, Union
 from uuid import uuid4
 
-import arrow
 import sqlalchemy.orm.exc
 from PyQt5.QtCore import QEvent, QObject, QSize, Qt, QTimer, pyqtBoundSignal, pyqtSignal, pyqtSlot
 from PyQt5.QtGui import (
@@ -869,9 +868,7 @@ def __lt__(self, other: SourceListWidgetItem) -> bool:
         if me and them:
             assert isinstance(me, SourceWidget)
             assert isinstance(them, SourceWidget)
-            my_ts = arrow.get(me.last_updated)
-            other_ts = arrow.get(them.last_updated)
-            return my_ts < other_ts
+            return me.last_updated < them.last_updated
         return True
 
 

client/securedrop_client/logic.py

@@ -22,11 +22,10 @@
 import logging
 import os
 import uuid
-from datetime import datetime
+from datetime import UTC, datetime
 from gettext import gettext as _
 from gettext import ngettext
 
-import arrow
 import sqlalchemy.orm.exc
 from PyQt5.QtCore import QObject, QProcess, QThread, QTimer, pyqtSignal, pyqtSlot
 from sqlalchemy.orm.session import sessionmaker
@@ -623,13 +622,13 @@ def authenticated(self) -> bool:
         """
         return bool(self.api and self.api.token is not None)
 
-    def get_last_sync(self):  # type: ignore[no-untyped-def]
+    def get_last_sync(self) -> datetime | None:
         """
         Returns the time of last synchronisation with the remote SD server.
         """
         try:
             with open(self.last_sync_filepath) as f:
-                return arrow.get(f.read())
+                return datetime.fromisoformat(f.read())
         except Exception:
             return None
 
@@ -648,7 +647,7 @@ def on_sync_success(self) -> None:
               successful
         """
         with open(self.last_sync_filepath, "w") as f:
-            f.write(arrow.now().format())
+            f.write(datetime.now(UTC).isoformat())
         self.show_last_sync()
 
         missing_files = storage.update_missing_files(self.data_dir, self.session)

client/securedrop_client/storage.py

@@ -28,7 +28,6 @@
 from pathlib import Path
 from typing import Any, TypeVar
 
-from dateutil.parser import parse
 from sqlalchemy import and_, desc, or_
 from sqlalchemy.exc import SQLAlchemyError
 from sqlalchemy.orm.exc import NoResultFound
@@ -332,7 +331,11 @@ def update_sources(
             lazy_setattr(local_source, "is_flagged", source.is_flagged)
             lazy_setattr(local_source, "interaction_count", source.interaction_count)
             lazy_setattr(local_source, "is_starred", source.is_starred)
-            lazy_setattr(local_source, "last_updated", parse(source.last_updated))
+            lazy_setattr(
+                local_source,
+                "last_updated",
+                datetime.fromisoformat(source.last_updated.replace("Z", "+00:00")),
+            )
             lazy_setattr(local_source, "public_key", source.key["public"])
             lazy_setattr(local_source, "fingerprint", source.key["fingerprint"])
 
@@ -360,7 +363,7 @@ def update_sources(
                 is_flagged=source.is_flagged,
                 interaction_count=source.interaction_count,
                 is_starred=source.is_starred,
-                last_updated=parse(source.last_updated),
+                last_updated=datetime.fromisoformat(source.last_updated.replace("Z", "+00:00")),
                 document_count=source.number_of_documents,
                 public_key=source.key["public"],
                 fingerprint=source.key["fingerprint"],

client/setup.py

@@ -21,7 +21,7 @@
     long_description=long_description,
     long_description_content_type="text/markdown",
     license="AGPLv3+",
-    install_requires=["SQLAlchemy", "alembic", "securedrop-sdk", "python-dateutil", "arrow"],
+    install_requires=["SQLAlchemy", "alembic", "securedrop-sdk"],
     python_requires=">=3.5",
     url="https://github.com/freedomofpress/securedrop-client",
     packages=setuptools.find_packages(include=["securedrop_client", "securedrop_client.*"]),

client/tests/gui/test_datetime_helpers.py

@@ -1,6 +1,6 @@
 import datetime
+from zoneinfo import ZoneInfo
 
-from dateutil import tz
 from PyQt5.QtCore import QByteArray
 
 from securedrop_client.gui.datetime_helpers import (
@@ -25,7 +25,7 @@ def test_localise_datetime(mocker):
     )
     evening_january_1_london = datetime.datetime(2023, 1, 1, 18, 0, 0, tzinfo=datetime.UTC)
     morning_january_2_auckland = datetime.datetime(
-        2023, 1, 2, 7, 0, 0, tzinfo=tz.gettz("Pacific/Auckland")
+        2023, 1, 2, 7, 0, 0, tzinfo=ZoneInfo("Pacific/Auckland")
     )
     assert localise_datetime(evening_january_1_london) == morning_january_2_auckland
 

client/tests/gui/test_main.py

@@ -3,6 +3,7 @@
 """
 
 import unittest
+from datetime import UTC, datetime, timedelta
 
 from PyQt5.QtWidgets import QHBoxLayout
 
@@ -326,13 +327,13 @@ def test_clear_error_status(mocker):
 
 def test_show_last_sync(mocker):
     """
-    If there's a value display the result of its "humanize" method.humanize
+    If there's a value display the formatted version of the timestamp.
     """
     w = Window()
     w.update_sync_status = mocker.MagicMock()
-    updated_on = mocker.MagicMock()
+    updated_on = datetime.now(UTC) - timedelta(seconds=5)
     w.show_last_sync(updated_on)
-    w.update_sync_status.assert_called_once_with(f"Last Refresh: {updated_on.humanize()}")
+    w.update_sync_status.assert_called_once_with("Last Refresh: 5 seconds")
 
 
 def test_show_last_sync_no_sync(mocker):

client/tests/test_logic.py

@@ -9,7 +9,6 @@
 from gettext import gettext as _
 from unittest.mock import Mock, call
 
-import arrow
 import pytest
 import sqlalchemy.orm.exc
 from PyQt5.QtTest import QSignalSpy
@@ -385,20 +384,20 @@ def test_Controller_last_sync_with_file(homedir, config, mocker, session_maker):
     """
     The flag indicating the time of the last sync with the API is stored in a
     dotfile in the user's home directory. If such a file exists, ensure an
-    "arrow" object (representing the date/time) is returned.
+    datetime object is returned.
     Using the `config` fixture to ensure the config is written to disk.
     """
     mock_gui = mocker.MagicMock()
 
     co = Controller("http://localhost", mock_gui, session_maker, homedir, None)
 
-    timestamp = "2018-10-10 18:17:13+01:00"
+    timestamp = "2018-10-10T18:17:13.045250+00:00"
     mocker.patch("builtins.open", mocker.mock_open(read_data=timestamp))
 
     result = co.get_last_sync()
 
-    assert isinstance(result, arrow.Arrow)
-    assert result.format() == timestamp
+    assert isinstance(result, datetime.datetime)
+    assert result.isoformat() == timestamp
 
 
 def test_Controller_last_sync_no_file(homedir, config, mocker, session_maker):

client/tests/test_storage.py

@@ -9,7 +9,6 @@
 from tempfile import TemporaryDirectory
 
 import pytest
-from dateutil.parser import parse
 from PyQt5.QtCore import QThread
 from sqlalchemy.exc import SQLAlchemyError
 from sqlalchemy.orm.exc import NoResultFound
@@ -406,7 +405,8 @@ def _is_equivalent_source(source, remote_source) -> bool:
         and source.fingerprint == remote_source.key["fingerprint"]
         and source.interaction_count == remote_source.interaction_count
         and source.is_starred == remote_source.is_starred
-        and source.last_updated == parse(remote_source.last_updated)
+        and source.last_updated
+        == datetime.datetime.fromisoformat(remote_source.last_updated.replace("Z", "+00:00"))
     )