Raise informative error when path nodes point to directories.

docs/source/changes.md

@@ -8,6 +8,8 @@ releases are available on [PyPI](https://pypi.org/project/pytask) and
 ## 0.4.3 - 2023-11-xx
 
 - {pull}`483` simplifies the teardown of a task.
+- {pull}`484` raises more informative error when directories instead of files are used
+  with path nodes.
 - {pull}`485` adds missing steps to unconfigure pytask after the job is done which
   caused flaky tests.
 

src/_pytask/collect.py

@@ -303,6 +303,10 @@ def pytask_collect_task(
 """
 
 
+_TEMPLATE_ERROR_DIRECTORY: str = """\
+The path '{path}' points to a directory, although only files are allowed."""
+
+
 @hookimpl(trylast=True)
 def pytask_collect_node(session: Session, path: Path, node_info: NodeInfo) -> PNode:
     """Collect a node of a task as a :class:`pytask.PNode`.
@@ -348,6 +352,9 @@ def pytask_collect_node(session: Session, path: Path, node_info: NodeInfo) -> PN
             node.path, session.config["paths"] or (session.config["root"],)
         )
 
+    if isinstance(node, PPathNode) and node.path.is_dir():
+        raise ValueError(_TEMPLATE_ERROR_DIRECTORY.format(path=node.path))
+
     if isinstance(node, PNode):
         return node
 
@@ -362,6 +369,10 @@ def pytask_collect_node(session: Session, path: Path, node_info: NodeInfo) -> PN
             node, session.config["check_casing_of_paths"]
         )
         name = shorten_path(node, session.config["paths"] or (session.config["root"],))
+
+        if isinstance(node, Path) and node.is_dir():
+            raise ValueError(_TEMPLATE_ERROR_DIRECTORY.format(path=path))
+
         return PathNode(name=name, path=node)
 
     node_name = create_name_of_python_node(node_info)

src/_pytask/execute.py

@@ -127,7 +127,7 @@ def pytask_execute_task_setup(session: Session, task: PTask) -> None:
     for dependency in session.dag.predecessors(task.signature):
         node = session.dag.nodes[dependency]["node"]
         if not node.state():
-            msg = f"{task.name} requires missing node {node.name}."
+            msg = f"{task.name!r} requires missing node {node.name!r}."
             if IS_FILE_SYSTEM_CASE_SENSITIVE:
                 msg += (
                     "\n\n(Hint: Your file-system is case-sensitive. Check the paths' "

tests/test_collect.py

@@ -572,3 +572,47 @@ def task_example(path: Annotated[Path, Path("file.txt"), Product]) -> None: ...
     result = runner.invoke(cli, [tmp_path.as_posix()])
     assert result.exit_code == ExitCode.COLLECTION_FAILED
     assert "is defined twice" in result.output
+
+
+@pytest.mark.parametrize(
+    "node",
+    [
+        "Path(__file__).parent",
+        "PathNode(name='path', path=Path(__file__).parent)",
+        "PickleNode(name='', path=Path(__file__).parent)",
+    ],
+)
+def test_error_when_path_dependency_is_directory(runner, tmp_path, node):
+    source = f"""
+    from pathlib import Path
+    from pytask import PickleNode, PathNode
+
+    def task_example(path = {node}): ...
+    """
+    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 all(i in result.output for i in ("only", "files", "are", "allowed"))
+
+
+@pytest.mark.parametrize(
+    "node",
+    [
+        "Path(__file__).parent",
+        "PathNode(name='path', path=Path(__file__).parent)",
+        "PickleNode(name='', path=Path(__file__).parent)",
+    ],
+)
+def test_error_when_path_product_is_directory(runner, tmp_path, node):
+    source = f"""
+    from pathlib import Path
+    from pytask import PickleNode, Product, PathNode
+    from typing_extensions import Annotated
+    from typing import Any
+
+    def task_example(path: Annotated[Any, Product] = {node}): ...
+    """
+    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 all(i in result.output for i in ("only", "files", "are", "allowed"))

tests/test_execute.py

@@ -1004,7 +1004,7 @@ def task_d(produces):
     result = runner.invoke(cli, [tmp_path.as_posix()])
 
     assert result.exit_code == ExitCode.FAILED
-    assert "NodeNotFoundError: task_d.py::task_d requires" in result.output
+    assert "NodeNotFoundError: 'task_d.py::task_d' requires" in result.output
 
 
 @pytest.mark.end_to_end()
@@ -1024,7 +1024,7 @@ def task_e(in1_: Annotated[Path, node1], in2_: Annotated[Any, node2]): ...
     result = runner.invoke(cli, [tmp_path.as_posix()])
 
     assert result.exit_code == ExitCode.FAILED
-    assert "NodeNotFoundError: task_e.py::task_e requires" in result.output
+    assert "NodeNotFoundError: 'task_e.py::task_e' requires" in result.output
     assert "input1" in result.output
 
 
@@ -1045,7 +1045,7 @@ def task_d(produces):
     result = runner.invoke(cli, [tmp_path.joinpath("src").as_posix()])
 
     assert result.exit_code == ExitCode.FAILED
-    assert "NodeNotFoundError: task_d.py::task_d requires" in result.output
+    assert "NodeNotFoundError: 'task_d.py::task_d' requires" in result.output
     assert "bld/in.txt" in result.output