Catch objects pretending to be PTask. (#508)

docs/source/changes.md

@@ -5,7 +5,7 @@ chronological order. Releases follow [semantic versioning](https://semver.org/)
 releases are available on [PyPI](https://pypi.org/project/pytask) and
 [Anaconda.org](https://anaconda.org/conda-forge/pytask).
 
-## 0.4.3 - 2023-11-xx
+## 0.4.3 - 2023-12-01
 
 - {pull}`483` simplifies the teardown of a task.
 - {pull}`484` raises more informative error when directories instead of files are used
@@ -26,6 +26,9 @@ releases are available on [PyPI](https://pypi.org/project/pytask) and
 - {pull}`498` fixes an error when using {class}`~pytask.Task` and
   {class}`~pytask.TaskWithoutPath` in task modules.
 - {pull}`500` refactors the dependencies for tests.
+- {pull}`501` removes `MetaNode`.
+- {pull}`508` catches objects that pretend to be a {class}`~pytask.PTask`. Fixes
+  {issue}`507`.
 
 ## 0.4.2 - 2023-11-08
 

src/_pytask/collect.py

@@ -22,7 +22,6 @@
 from _pytask.console import get_file
 from _pytask.console import is_jupyter
 from _pytask.exceptions import CollectionError
-from _pytask.mark import MarkGenerator
 from _pytask.mark_utils import get_all_marks
 from _pytask.mark_utils import has_mark
 from _pytask.node_protocols import PNode
@@ -176,10 +175,7 @@ def pytask_collect_file(
 
         collected_reports = []
         for name, obj in inspect.getmembers(mod):
-            # Skip mark generator since it overrides __getattr__ and seems like any
-            # object. Happens when people do ``from pytask import mark`` and
-            # ``@mark.x``.
-            if isinstance(obj, MarkGenerator):
+            if _is_filtered_object(obj):
                 continue
 
             # Ensures that tasks with this decorator are only collected once.
@@ -196,6 +192,26 @@ def pytask_collect_file(
     return None
 
 
+def _is_filtered_object(obj: Any) -> bool:
+    """Filter some objects that are only causing harm later on.
+
+    See :issue:`507`.
+
+    """
+    # Filter :class:`pytask.Task` and :class:`pytask.TaskWithoutPath` objects.
+    if isinstance(obj, PTask) and inspect.isclass(obj):
+        return True
+
+    # Filter objects overwriting the ``__getattr__`` method like :class:`pytask.mark` or
+    # ``from ibis import _``.
+    attr_name = "attr_that_definitely_does_not_exist"
+    if hasattr(obj, attr_name) and not bool(
+        inspect.getattr_static(obj, attr_name, False)
+    ):
+        return True
+    return False
+
+
 @hookimpl
 def pytask_collect_task_protocol(
     session: Session, path: Path | None, name: str, obj: Any
@@ -279,7 +295,7 @@ def pytask_collect_task(
             markers=markers,
             attributes={"collection_id": collection_id, "after": after},
         )
-    if isinstance(obj, PTask) and not inspect.isclass(obj):
+    if isinstance(obj, PTask):
         return obj
     return None
 

src/_pytask/mark_utils.py

@@ -5,7 +5,6 @@
 """
 from __future__ import annotations
 
-import inspect
 from typing import Any
 from typing import TYPE_CHECKING
 
@@ -19,12 +18,10 @@
 
 def get_all_marks(obj_or_task: Any | PTask) -> list[Mark]:
     """Get all marks from a callable or task."""
-    if isinstance(obj_or_task, PTask) and not inspect.isclass(obj_or_task):
-        marks = obj_or_task.markers
-    else:
-        obj = obj_or_task
-        marks = obj.pytask_meta.markers if hasattr(obj, "pytask_meta") else []
-    return marks
+    if isinstance(obj_or_task, PTask):
+        return obj_or_task.markers
+    obj = obj_or_task
+    return obj.pytask_meta.markers if hasattr(obj, "pytask_meta") else []
 
 
 def set_marks(obj_or_task: Any | PTask, marks: list[Mark]) -> Any | PTask:

src/_pytask/nodes.py

@@ -27,7 +27,7 @@
     from _pytask.mark import Mark
 
 
-__all__ = ["PathNode", "PythonNode", "Task", "TaskWithoutPath"]
+__all__ = ["PathNode", "PickleNode", "PythonNode", "Task", "TaskWithoutPath"]
 
 
 @define(kw_only=True)

src/_pytask/typing.py

@@ -13,7 +13,13 @@
     from typing_extensions import TypeAlias
 
 
-__all__ = ["Product", "ProductType"]
+__all__ = [
+    "NoDefault",
+    "Product",
+    "ProductType",
+    "is_task_function",
+    "no_default",
+]
 
 
 @define(frozen=True)

tests/test_collect.py

@@ -684,7 +684,12 @@ def task_mixed(): pass
 @pytest.mark.end_to_end()
 def test_module_can_be_collected(runner, tmp_path):
     source = """
-    from pytask import Task, TaskWithoutPath
+    from pytask import Task, TaskWithoutPath, mark
+
+    class C:
+        def __getattr__(self, name):
+            return C()
+    c = C()
     """
     tmp_path.joinpath("task_example.py").write_text(textwrap.dedent(source))