Add error message for not collected tasks with @task decorator. (#521)

docs/source/changes.md

@@ -12,6 +12,9 @@ releases are available on [PyPI](https://pypi.org/project/pytask) and
   (fixes #514). It also warns if the path is configured as a string and not a list of
   strings.
 - {pull}`519` raises an error when builtin functions are wrapped with
+  {func}`~pytask.task`. Closes {issue}`512`.pull
+- {pull}`521` raises an error message when imported functions are wrapped with
+  {func}`@task <pytask.task>` in a task module. Fixes {issue}`513`.
   {func}`~pytask.task`. Closes {issue}`512`.
 - {pull}`522` improves the issue templates.
 - {pull}`523` refactors `_pytask.console._get_file`.

src/_pytask/collect.py

@@ -21,6 +21,7 @@
 from _pytask.console import create_summary_panel
 from _pytask.console import get_file
 from _pytask.exceptions import CollectionError
+from _pytask.exceptions import NodeNotCollectedError
 from _pytask.mark_utils import get_all_marks
 from _pytask.mark_utils import has_mark
 from _pytask.node_protocols import PNode
@@ -37,6 +38,7 @@
 from _pytask.path import shorten_path
 from _pytask.reports import CollectionReport
 from _pytask.shared import find_duplicates
+from _pytask.task_utils import COLLECTED_TASKS
 from _pytask.task_utils import task as task_decorator
 from _pytask.typing import is_task_function
 from rich.text import Text
@@ -61,6 +63,7 @@ def pytask_collect(session: Session) -> bool:
 
     _collect_from_paths(session)
     _collect_from_tasks(session)
+    _collect_not_collected_tasks(session)
 
     session.tasks.extend(
         i.node
@@ -108,6 +111,9 @@ def _collect_from_tasks(session: Session) -> None:
             path = get_file(raw_task)
             name = raw_task.pytask_meta.name
 
+        if has_mark(raw_task, "task"):
+            COLLECTED_TASKS[path].remove(raw_task)
+
         # When a task is not a callable, it can be anything or a PTask. Set arbitrary
         # values and it will pass without errors and not collected.
         else:
@@ -126,6 +132,45 @@ def _collect_from_tasks(session: Session) -> None:
             session.collection_reports.append(report)
 
 
+_FAILED_COLLECTING_TASK = """\
+Failed to collect task '{name}'{path_desc}.
+
+This can happen when the task function is defined in another module, imported to a \
+task module and wrapped with the '@task' decorator.
+
+To collect this task correctly, wrap the imported function in a lambda expression like
+
+task(...)(lambda **x: imported_function(**x)).
+"""
+
+
+def _collect_not_collected_tasks(session: Session) -> None:
+    """Collect tasks that are not collected yet and create failed reports."""
+    for path in list(COLLECTED_TASKS):
+        tasks = COLLECTED_TASKS.pop(path)
+        for task in tasks:
+            name = task.pytask_meta.name  # type: ignore[attr-defined]
+            node: PTask
+            if path:
+                node = Task(base_name=name, path=path, function=task)
+                path_desc = f" in '{path}'"
+            else:
+                node = TaskWithoutPath(name=name, function=task)
+                path_desc = ""
+            report = CollectionReport(
+                outcome=CollectionOutcome.FAIL,
+                node=node,
+                exc_info=(
+                    NodeNotCollectedError,
+                    NodeNotCollectedError(
+                        _FAILED_COLLECTING_TASK.format(name=name, path_desc=path_desc)
+                    ),
+                    None,
+                ),
+            )
+            session.collection_reports.append(report)
+
+
 @hookimpl
 def pytask_ignore_collect(path: Path, config: dict[str, Any]) -> bool:
     """Ignore a path during the collection."""

src/_pytask/console.py

@@ -225,18 +225,13 @@ def get_file(  # noqa: PLR0911
             return get_file(function.__wrapped__)
     source_file = inspect.getsourcefile(function)
     if source_file:
-        # Handle functions defined in the REPL.
         if "<stdin>" in source_file:
             return None
-        # Handle lambda functions.
         if "<string>" in source_file:
             try:
                 return Path(function.__globals__["__file__"]).absolute().resolve()
             except KeyError:
                 return None
-        # Handle functions defined in Jupyter notebooks.
-        if "ipykernel" in source_file or "ipython-input" in source_file:
-            return None
         return Path(source_file).absolute().resolve()
     return None
 

src/_pytask/task.py

@@ -76,6 +76,7 @@ def _raise_error_when_task_functions_are_duplicated(
     msg = (
         "There are some duplicates among the repeated tasks. It happens when you define"
         "the task function outside the loop body and merely wrap in the loop body with "
-        f"the '@task(...)' decorator.\n\n{flat_tree}"
+        "the 'task(...)(func)' decorator. As a workaround, wrap the task function in "
+        f"a lambda expression like 'task(...)(lambda **x: func(**x))'.\n\n{flat_tree}"
     )
     raise ValueError(msg)

tests/test_task.py

@@ -679,3 +679,30 @@ def test_raise_error_with_builtin_function_as_task(runner, tmp_path):
     result = runner.invoke(cli, [tmp_path.as_posix()])
     assert result.exit_code == ExitCode.COLLECTION_FAILED
     assert "Builtin functions cannot be wrapped" in result.output
+
+
+def test_task_function_in_another_module(runner, tmp_path):
+    source = """
+    def func():
+        return "Hello, World!"
+    """
+    tmp_path.joinpath("module.py").write_text(textwrap.dedent(source))
+
+    source = """
+    from pytask import task
+    from pathlib import Path
+    from _pytask.path import import_path
+    import inspect
+
+    _ROOT_PATH = Path(__file__).parent
+
+    module = import_path(_ROOT_PATH / "module.py", _ROOT_PATH)
+    name_to_obj = dict(inspect.getmembers(module))
+
+    task(produces=Path("out.txt"))(name_to_obj["func"])
+    """
+    tmp_path.joinpath("task_example.py").write_text(textwrap.dedent(source))
+
+    result = runner.invoke(cli, [tmp_path.as_posix()])
+    assert result.exit_code == ExitCode.COLLECTION_FAILED
+    assert "1  Failed" in result.output