Test: Common Crash Locations in Task

src/crystal/tests/index.py

@@ -23,6 +23,7 @@
     test_server,
     test_shell,
     test_ssd,
+    test_task_crashes,
     test_tasks,
     test_tasktree,
     test_workflows,
@@ -85,6 +86,7 @@ def _test_functions_in_module(mod) -> List[Callable]:
     _test_functions_in_module(test_server) +
     _test_functions_in_module(test_shell) +
     _test_functions_in_module(test_ssd) +
+    _test_functions_in_module(test_task_crashes) +
     _test_functions_in_module(test_tasks) +
     _test_functions_in_module(test_tasktree) +
     _test_functions_in_module(test_workflows) +

src/crystal/tests/test_task_crashes.py

@@ -0,0 +1,229 @@
+from crystal.task import (
+    DownloadResourceGroupTask, DownloadResourceGroupMembersTask, DownloadResourceTask,
+    UpdateResourceGroupMembersTask
+)
+from crystal.tests.util.server import served_project
+from crystal.tests.util.tasks import (
+    clear_top_level_tasks_on_exit, scheduler_disabled
+)
+from crystal.tests.util.wait import wait_for
+from crystal.tests.util.windows import OpenOrCreateDialog
+from crystal.model import Project, Resource, ResourceGroup
+from crystal.util.xfutures import Future
+from crystal.util.xthreading import bg_call_later
+from typing import Callable, Optional, TypeVar
+from unittest.mock import patch
+
+
+_R = TypeVar('_R')
+
+
+# ------------------------------------------------------------------------------
+# Test: Common Crash Locations in Task
+# 
+# Below, some abbreviations are used in test names:
+# - T = Task
+# - DRT = DownloadResourceTask
+# - DRGMT = DownloadResourceGroupMembersTask
+# - DRGT = DownloadResourceGroupTask
+
+async def test_when_T_try_get_next_task_unit_crashes_then_T_displays_as_crashed() -> None:
+    with scheduler_disabled, served_project('testdata_xkcd.crystalproj.zip') as sp:
+        # Define URLs
+        home_url = sp.get_request_url('https://xkcd.com/')
+
+        async with (await OpenOrCreateDialog.wait_for()).create() as (mw, _):
+            project = Project._last_opened_project
+            assert project is not None
+
+            with clear_top_level_tasks_on_exit(project):
+                # Create DownloadResourceTask
+                home_r = Resource(project, home_url)
+                home_r.download()
+                (download_r_task,) = project.root_task.children
+                assert isinstance(download_r_task, DownloadResourceTask)
+
+                # Force DownloadResourceTask into an illegal state
+                # (i.e. a container task with empty children)
+                # which should crash the next call to DRG.try_get_next_task_unit()
+                assert len(download_r_task.children) > 0
+                download_r_task._children = []
+
+                # Precondition
+                assert download_r_task.crash_reason is None
+
+                unit = project.root_task.try_get_next_task_unit()  # step scheduler
+                assert unit is None
+
+                # Postcondition
+                assert download_r_task.crash_reason is not None
+
+
+async def test_when_DRT_child_task_did_complete_event_crashes_then_DRT_displays_as_crashed() -> None:
+    with scheduler_disabled, served_project('testdata_xkcd.crystalproj.zip') as sp:
+        # Define URLs
+        home_url = sp.get_request_url('https://xkcd.com/')
+
+        async with (await OpenOrCreateDialog.wait_for()).create() as (mw, _):
+            project = Project._last_opened_project
+            assert project is not None
+
+            with clear_top_level_tasks_on_exit(project):
+                # Create DownloadResourceTask
+                home_r = Resource(project, home_url)
+                home_r.download()
+                (download_r_task,) = project.root_task.children
+                assert isinstance(download_r_task, DownloadResourceTask)
+
+                # Precondition
+                assert download_r_task.crash_reason is None
+
+                # Download URL
+                unit = project.root_task.try_get_next_task_unit()  # step scheduler
+                assert unit is not None
+                await _bg_call_and_wait(unit)
+
+                # Parse links
+                unit = project.root_task.try_get_next_task_unit()  # step scheduler
+                assert unit is not None
+                # Patch urljoin() to simulate effect of calling urlparse('//[oops'),
+                # which raises an exception in stock Python:
+                # https://discuss.python.org/t/urlparse-can-sometimes-raise-an-exception-should-it/44465
+                # 
+                # NOTE: Overrides the fix in commit 5aaaba57076d537a4872bb3cf7270112ca497a06,
+                #       reintroducing the related bug it fixed.
+                with patch('crystal.task.urljoin', sideeffect=ValueError('Invalid IPv6 URL')):
+                    await _bg_call_and_wait(unit)
+
+                # Postcondition:
+                # Ensure crashed in DownloadResourceTask.child_task_did_complete(),
+                # when tried to resolve relative_urls from links parsed by
+                # ParseResourceRevisionLinks to absolute URLs
+                assert download_r_task.crash_reason is not None
+
+
+async def test_when_DRGMT_load_children_crashes_then_DRGT_displays_as_crashed() -> None:
+    with scheduler_disabled, served_project('testdata_xkcd.crystalproj.zip') as sp:
+        # Define URLs
+        atom_feed_url = sp.get_request_url('https://xkcd.com/atom.xml')
+        rss_feed_url = sp.get_request_url('https://xkcd.com/rss.xml')
+        feed_pattern = sp.get_request_url('https://xkcd.com/*.xml')
+
+        async with (await OpenOrCreateDialog.wait_for()).create() as (mw, _):
+            project = Project._last_opened_project
+            assert project is not None
+
+            with clear_top_level_tasks_on_exit(project):
+                atom_feed_r = Resource(project, atom_feed_url)
+                rss_feed_r = Resource(project, rss_feed_url)
+
+                # Create DownloadResourceGroupMembersTask
+                feed_g = ResourceGroup(project, '', feed_pattern, source=None)
+                feed_g.download()
+                (download_rg_task,) = project.root_task.children
+                assert isinstance(download_rg_task, DownloadResourceGroupTask)
+                (update_rg_members_task, download_rg_members_task) = download_rg_task.children
+                assert isinstance(update_rg_members_task, UpdateResourceGroupMembersTask)
+                assert isinstance(download_rg_members_task, DownloadResourceGroupMembersTask)
+
+                # Capture download_rg_members_task.{_pdb, _children_loaded, subtitle}
+                # after exiting DownloadResourceGroupMembersTask.__init__()
+                pbc_after_init = download_rg_members_task._pbc
+                children_loaded_after_init = download_rg_members_task._children_loaded
+                subtitle_after_init = download_rg_members_task.subtitle
+                assert None == pbc_after_init
+                assert False == children_loaded_after_init
+                assert 'Queued' == subtitle_after_init
+
+                super_initialize_children = download_rg_members_task.initialize_children
+                def initialize_children(self, *args, **kwargs):
+                    # Restore self.{_pdb, _children_loaded, subtitle} to original state
+                    # after exiting DownloadResourceGroupMembersTask.__init__()
+                    self._pbc = pbc_after_init
+                    self._children_loaded = children_loaded_after_init
+                    self.subtitle = subtitle_after_init
+
+                    return super_initialize_children(*args, **kwargs)
+
+                # Precondition
+                assert download_rg_members_task.crash_reason is None
+
+                # Load children of DownloadResourceGroupMembersTask
+                unit = project.root_task.try_get_next_task_unit()  # step scheduler
+                assert unit is not None
+                # Patch DownloadResourceGroupMembersTask.initialize_children() to reintroduce
+                # a bug in DownloadResourceGroupMembersTask._load_children() that was
+                # fixed in commit 44f5bd429201972d324df1287e673ddef9ffa936
+                with patch.object(download_rg_members_task, 'initialize_children', initialize_children):
+                    await _bg_call_and_wait(unit)
+
+                # Postcondition
+                assert download_rg_members_task.crash_reason is not None
+
+
+async def test_when_DRGMT_group_did_add_member_event_crashes_then_DRGT_displays_as_crashed() -> None:
+    with scheduler_disabled, served_project('testdata_xkcd.crystalproj.zip') as sp:
+        # Define URLs
+        atom_feed_url = sp.get_request_url('https://xkcd.com/atom.xml')
+        rss_feed_url = sp.get_request_url('https://xkcd.com/rss.xml')
+        feed_pattern = sp.get_request_url('https://xkcd.com/*.xml')
+
+        async with (await OpenOrCreateDialog.wait_for()).create() as (mw, _):
+            project = Project._last_opened_project
+            assert project is not None
+
+            with clear_top_level_tasks_on_exit(project):
+                atom_feed_r = Resource(project, atom_feed_url)
+
+                # Create DownloadResourceGroupMembersTask
+                feed_g = ResourceGroup(project, '', feed_pattern, source=None)
+                feed_g.download()
+                (download_rg_task,) = project.root_task.children
+                assert isinstance(download_rg_task, DownloadResourceGroupTask)
+                (update_rg_members_task, download_rg_members_task) = download_rg_task.children
+                assert isinstance(update_rg_members_task, UpdateResourceGroupMembersTask)
+                assert isinstance(download_rg_members_task, DownloadResourceGroupMembersTask)
+
+                super_notify_did_append_child = download_rg_members_task.notify_did_append_child
+                def notify_did_append_child(self, *args, **kwargs):
+                    super_notify_did_append_child(*args, **kwargs)
+
+                    # Simulate failure of `self._pbc.total += 1`
+                    # due to self._pbc being None
+                    raise AttributeError("'NoneType' object has no attribute 'total'")
+
+                # Precondition
+                assert download_rg_members_task.crash_reason is None
+
+                with patch.object(download_rg_members_task, 'notify_did_append_child', notify_did_append_child):
+                    rss_feed_r = Resource(project, rss_feed_url)
+
+                # Postcondition
+                assert download_rg_members_task.crash_reason is not None
+
+
+# ------------------------------------------------------------------------------
+# Utility
+
+async def _bg_call_and_wait(callable: Callable[[], _R], *, timeout: Optional[float]=None) -> _R:
+    """
+    Start the specified callable on a background thread and
+    waits for it to finish running.
+    
+    The foreground thread IS released while waiting, so the callable can safely
+    make calls to fg_call_later() and fg_call_and_wait() without deadlocking.
+    """
+    result_cell = Future()  # type: Future[_R]
+    def bg_task() -> None:
+        result_cell.set_running_or_notify_cancel()
+        try:
+            result_cell.set_result(callable())
+        except BaseException as e:
+            result_cell.set_exception(e)
+    bg_call_later(bg_task)
+    # NOTE: Releases foreground thread while waiting
+    await wait_for(lambda: result_cell.done() or None, timeout)
+    return result_cell.result()
+
+
+# ------------------------------------------------------------------------------

src/crystal/tests/test_tasks.py

@@ -1,25 +1,21 @@
 from crystal.task import (
     ASSUME_RESOURCES_DOWNLOADED_IN_SESSION_WILL_ALWAYS_REMAIN_FRESH,
-    ProjectFreeSpaceTooLowError, Task
+    ProjectFreeSpaceTooLowError, Task,
 )
 from crystal.tests.util.asserts import *
 from crystal.tests.util.data import (
     MAX_TIME_TO_DOWNLOAD_404_URL,
     MAX_TIME_TO_DOWNLOAD_XKCD_HOME_URL_BODY
 )
 from crystal.tests.util.downloads import load_children_of_drg_task
-from crystal.tests.util.runner import bg_sleep
-from crystal.tests.util.screenshots import screenshot_if_raises
 from crystal.tests.util.server import served_project
 from crystal.tests.util.skip import skipTest
 from crystal.tests.util.subtests import SubtestsContext, awith_subtests
 from crystal.tests.util.wait import wait_for
 from crystal.tests.util.windows import OpenOrCreateDialog
-from crystal.model import Project, Resource, ResourceGroup, RootResource
+from crystal.model import Project, Resource, ResourceGroup
 from crystal.util.progress import ProgressBarCalculator
 from crystal.util.xcollections.lazy import AppendableLazySequence
-import tempfile
-from tqdm import tqdm
 from typing import NamedTuple
 from unittest import skip
 from unittest.mock import patch, Mock, PropertyMock
@@ -207,8 +203,7 @@ async def try_download_with_disk_usage(du: _DiskUsage, *, expect_failure: bool)
     with subtests.test('given project on small disk and less than 5 percent of disk free'):
         with served_project('testdata_xkcd.crystalproj.zip') as sp:
             # Define URLs
-            if True:
-                home_url = sp.get_request_url('https://xkcd.com/')
+            home_url = sp.get_request_url('https://xkcd.com/')
 
             async with (await OpenOrCreateDialog.wait_for()).create() as (mw, _):
                 project = Project._last_opened_project
@@ -225,8 +220,7 @@ async def try_download_with_disk_usage(du: _DiskUsage, *, expect_failure: bool)
     with subtests.test('given project on large disk and less than 4 gib of disk free'):
         with served_project('testdata_xkcd.crystalproj.zip') as sp:
             # Define URLs
-            if True:
-                home_url = sp.get_request_url('https://xkcd.com/')
+            home_url = sp.get_request_url('https://xkcd.com/')
 
             async with (await OpenOrCreateDialog.wait_for()).create() as (mw, _):
                 project = Project._last_opened_project

src/crystal/tests/test_tasktree.py

@@ -15,6 +15,10 @@
 from crystal.tests.util.data import MAX_TIME_TO_DOWNLOAD_404_URL
 from crystal.tests.util.downloads import load_children_of_drg_task
 from crystal.tests.util.server import served_project
+from crystal.tests.util.tasks import (
+    mark_as_complete as _mark_as_complete,
+    scheduler_disabled,
+)
 from crystal.tests.util.wait import tree_has_no_children_condition, wait_for, wait_while
 from crystal.tests.util.windows import MainWindow, OpenOrCreateDialog
 from crystal.ui.tree2 import NodeView
@@ -560,7 +564,7 @@ async def _project_with_resource_group_starting_to_download(
         raise ValueError()
 
     scheduler_patched = (
-        patch('crystal.task.start_schedule_forever', lambda task: None)
+        scheduler_disabled
         if not scheduler_thread_enabled
         else cast(AbstractContextManager, nullcontext())
     )  # type: AbstractContextManager
@@ -745,24 +749,3 @@ def _value_of_more_node(tn: NodeView) -> Optional[int]:
 
 def _is_complete(tn: NodeView) -> bool:
     return tn.subtitle == 'Complete'
-
-
-def _mark_as_complete(task: Task) -> None:
-    assert not task.complete
-    task.finish()
-    assert task.complete
-
-
-class _NullTask(_PlaceholderTask):
-    """
-    Null task. For special purposes.
-    
-    This task is always complete immediately after initialization.
-    """
-    def __init__(self) -> None:
-        super().__init__(title='<null>', prefinish=True)
-
-    def __repr__(self) -> str:
-        return f'<_NullTask>'
-
-_NULL_TASK = _NullTask()

src/crystal/tests/util/tasks.py

@@ -1,6 +1,9 @@
 from __future__ import annotations
 
+from contextlib import contextmanager
+from crystal.model import Project
 import crystal.task
+from crystal.task import Task
 from crystal.tests.util.controls import TreeItem
 from crystal.tests.util.runner import bg_sleep
 from crystal.tests.util.wait import (
@@ -9,7 +12,8 @@
 )
 import math
 import re
-from typing import Callable, List, Optional
+from typing import Callable, List, Iterator, Optional
+from unittest.mock import patch
 import wx
 
 
@@ -119,4 +123,31 @@ def first_task_title():
     return first_task_title
 
 
+# ------------------------------------------------------------------------------
+# Utility: Scheduler Manual Control
+
+scheduler_disabled = patch('crystal.task.start_schedule_forever', lambda task: None)
+
+
+def mark_as_complete(task: Task) -> None:
+    assert not task.complete
+    task.finish()
+    assert task.complete
+
+
+@contextmanager
+def clear_top_level_tasks_on_exit(project: Project) -> Iterator[None]:
+    try:
+        yield
+    finally:
+        # Force root task children to complete
+        for c in project.root_task.children:
+            if not c.complete:
+                mark_as_complete(c)
+
+        # Clear root task children
+        assert None == project.root_task.try_get_next_task_unit()
+        assert len(project.root_task.children) == 0
+
+
 # ------------------------------------------------------------------------------