Fix PythonNode when used as return.

docs/source/changes.md

@@ -10,6 +10,7 @@ releases are available on [PyPI](https://pypi.org/project/pytask) and
 - {pull}`443` ensures that `PythonNode.name` is always unique by only handling it
   internally.
 - {pull}`444` moves all content of `setup.cfg` to `pyproject.toml`.
+- {pull}`446` refactors `create_name_of_python_node` and fixes `PythonNode`s as returns.
 - {pull}`447` fixes handling multiple product annotations of a task.
 
 ## 0.4.0 - 2023-10-07

src/_pytask/collect.py

@@ -12,6 +12,7 @@
 from typing import Iterable
 from typing import TYPE_CHECKING
 
+from _pytask.collect_utils import create_name_of_python_node
 from _pytask.collect_utils import parse_dependencies_from_task_function
 from _pytask.collect_utils import parse_products_from_task_function
 from _pytask.config import hookimpl
@@ -305,7 +306,7 @@ def pytask_collect_task(
 
 @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.nodes.PathNode`.
+    """Collect a node of a task as a :class:`pytask.PNode`.
 
     Strings are assumed to be paths. This might be a strict assumption, but since this
     hook is executed at last and possible errors will be shown, it seems reasonable and
@@ -325,8 +326,7 @@ def pytask_collect_node(session: Session, path: Path, node_info: NodeInfo) -> PN
     node = node_info.value
 
     if isinstance(node, PythonNode):
-        node_name = _create_name_of_python_node(node_info)
-        node.name = node_name
+        node.name = create_name_of_python_node(node_info)
         return node
 
     if isinstance(node, PPathNode) and not node.path.is_absolute():
@@ -354,7 +354,7 @@ def pytask_collect_node(session: Session, path: Path, node_info: NodeInfo) -> PN
         )
         return PathNode.from_path(node)
 
-    node_name = _create_name_of_python_node(node_info)
+    node_name = create_name_of_python_node(node_info)
     return PythonNode(value=node, name=node_name)
 
 
@@ -494,17 +494,3 @@ def pytask_collect_log(
         )
 
         raise CollectionError
-
-
-def _create_name_of_python_node(node_info: NodeInfo) -> str:
-    """Create name of PythonNode."""
-    prefix = (
-        node_info.task_path.as_posix() + "::" + node_info.task_name
-        if node_info.task_path
-        else node_info.task_name
-    )
-    node_name = prefix + "::" + node_info.arg_name
-    if node_info.path:
-        suffix = "-".join(map(str, node_info.path))
-        node_name += "::" + suffix
-    return node_name

src/_pytask/collect_utils.py

@@ -11,6 +11,7 @@
 from typing import Iterable
 from typing import TYPE_CHECKING
 
+import attrs
 from _pytask._inspect import get_annotations
 from _pytask.exceptions import NodeNotCollectedError
 from _pytask.mark_utils import has_mark
@@ -24,6 +25,7 @@
 from _pytask.tree_util import tree_leaves
 from _pytask.tree_util import tree_map
 from _pytask.tree_util import tree_map_with_path
+from _pytask.typing import no_default
 from _pytask.typing import ProductType
 from attrs import define
 from attrs import field
@@ -327,9 +329,15 @@ def parse_dependencies_from_task_function(
             isinstance(x, PythonNode) and not x.hash for x in tree_leaves(nodes)
         )
         if not isinstance(nodes, PNode) and are_all_nodes_python_nodes_without_hash:
-            prefix = task_path.as_posix() + "::" + task_name if task_path else task_name
-            node_name = prefix + "::" + parameter_name
-
+            node_name = create_name_of_python_node(
+                NodeInfo(
+                    arg_name=parameter_name,
+                    path=(),
+                    value=value,
+                    task_path=task_path,
+                    task_name=task_name,
+                )
+            )
             dependencies[parameter_name] = PythonNode(value=value, name=node_name)
         else:
             dependencies[parameter_name] = nodes
@@ -606,6 +614,13 @@ def _collect_dependency(
     """
     node = node_info.value
 
+    if isinstance(node, PythonNode) and node.value is no_default:
+        # If a node is a dependency and its value is not set, the node is a product in
+        # another task and the value will be set there. Thus, we wrap the original node
+        # in another node to retrieve the value after it is set.
+        new_node = attrs.evolve(node, value=node)
+        node_info = node_info._replace(value=new_node)
+
     collected_node = session.hook.pytask_collect_node(
         session=session, path=path, node_info=node_info
     )
@@ -653,10 +668,25 @@ def _collect_product(
     collected_node = session.hook.pytask_collect_node(
         session=session, path=path, node_info=node_info
     )
+
     if collected_node is None:
         msg = (
             f"{node!r} can't be parsed as a product for task {task_name!r} in {path!r}."
         )
         raise NodeNotCollectedError(msg)
 
     return collected_node
+
+
+def create_name_of_python_node(node_info: NodeInfo) -> str:
+    """Create name of PythonNode."""
+    prefix = (
+        node_info.task_path.as_posix() + "::" + node_info.task_name
+        if node_info.task_path
+        else node_info.task_name
+    )
+    node_name = prefix + "::" + node_info.arg_name
+    if node_info.path:
+        suffix = "-".join(map(str, node_info.path))
+        node_name += "::" + suffix
+    return node_name

src/_pytask/dag.py

@@ -29,7 +29,7 @@
 from _pytask.node_protocols import PPathNode
 from _pytask.node_protocols import PTask
 from _pytask.node_protocols import PTaskWithPath
-from _pytask.path import find_common_ancestor_of_nodes
+from _pytask.nodes import PythonNode
 from _pytask.report import DagReport
 from _pytask.shared import reduce_names_of_multiple_nodes
 from _pytask.shared import reduce_node_name
@@ -87,6 +87,16 @@ def pytask_dag_create_dag(tasks: list[PTask]) -> nx.DiGraph:
         tree_map(lambda x: dag.add_node(x.name, node=x), task.produces)
         tree_map(lambda x: dag.add_edge(task.name, x.name), task.produces)
 
+        # If a node is a PythonNode wrapped in another PythonNode, it is a product from
+        # another task that is a dependency in the current task. Thus, draw an edge
+        # connecting the two nodes.
+        tree_map(
+            lambda x: dag.add_edge(x.value.name, x.name)
+            if isinstance(x, PythonNode) and isinstance(x.value, PythonNode)
+            else None,
+            task.depends_on,
+        )
+
     _check_if_dag_has_cycles(dag)
 
     return dag
@@ -114,7 +124,7 @@ def pytask_dag_select_execution_dag(session: Session, dag: nx.DiGraph) -> None:
 def pytask_dag_validate_dag(session: Session, dag: nx.DiGraph) -> None:
     """Validate the DAG."""
     _check_if_root_nodes_are_available(dag, session.config["paths"])
-    _check_if_tasks_have_the_same_products(dag)
+    _check_if_tasks_have_the_same_products(dag, session.config["paths"])
 
 
 def _have_task_or_neighbors_changed(
@@ -292,7 +302,7 @@ def _format_dictionary_to_tree(dict_: dict[str, list[str]], title: str) -> str:
     return render_to_string(tree, console=console, strip_styles=True)
 
 
-def _check_if_tasks_have_the_same_products(dag: nx.DiGraph) -> None:
+def _check_if_tasks_have_the_same_products(dag: nx.DiGraph, paths: list[Path]) -> None:
     nodes_created_by_multiple_tasks = []
 
     for node in dag.nodes:
@@ -303,19 +313,11 @@ def _check_if_tasks_have_the_same_products(dag: nx.DiGraph) -> None:
                 nodes_created_by_multiple_tasks.append(node)
 
     if nodes_created_by_multiple_tasks:
-        all_names = nodes_created_by_multiple_tasks + [
-            predecessor
-            for node in nodes_created_by_multiple_tasks
-            for predecessor in dag.predecessors(node)
-        ]
-        common_ancestor = find_common_ancestor_of_nodes(*all_names)
         dictionary = {}
         for node in nodes_created_by_multiple_tasks:
-            short_node_name = reduce_node_name(
-                dag.nodes[node]["node"], [common_ancestor]
-            )
+            short_node_name = reduce_node_name(dag.nodes[node]["node"], paths)
             short_predecessors = reduce_names_of_multiple_nodes(
-                dag.predecessors(node), dag, [common_ancestor]
+                dag.predecessors(node), dag, paths
             )
             dictionary[short_node_name] = short_predecessors
         text = _format_dictionary_to_tree(dictionary, "Products from multiple tasks:")

src/_pytask/nodes.py

@@ -13,6 +13,8 @@
 from _pytask.node_protocols import PPathNode
 from _pytask.node_protocols import PTask
 from _pytask.node_protocols import PTaskWithPath
+from _pytask.typing import no_default
+from _pytask.typing import NoDefault
 from attrs import define
 from attrs import field
 
@@ -47,9 +49,7 @@ class TaskWithoutPath(PTask):
         A list of markers attached to the task function.
     report_sections
         Reports with entries for when, what, and content.
-
-    Attributes
-    ----------
+    attributes: dict[Any, Any]
         A dictionary to store additional information of the task.
     """
 
@@ -79,6 +79,8 @@ def execute(self, **kwargs: Any) -> None:
 class Task(PTaskWithPath):
     """The class for tasks which are Python functions.
 
+    Attributes
+    ----------
     base_name
         The base name of the task.
     path
@@ -97,9 +99,7 @@ class Task(PTaskWithPath):
         A list of markers attached to the task function.
     report_sections
         Reports with entries for when, what, and content.
-
-    Attributes
-    ----------
+    attributes: dict[Any, Any]
         A dictionary to store additional information of the task.
 
     """
@@ -204,11 +204,13 @@ class PythonNode(PNode):
     """
 
     name: str = ""
-    value: Any = None
+    value: Any | NoDefault = no_default
     hash: bool | Callable[[Any], bool] = False  # noqa: A003
 
     def load(self) -> Any:
         """Load the value."""
+        if isinstance(self.value, PythonNode):
+            return self.value.load()
         return self.value
 
     def save(self, value: Any) -> None:
@@ -234,11 +236,12 @@ def state(self) -> str | None:
 
         """
         if self.hash:
+            value = self.load()
             if callable(self.hash):
-                return str(self.hash(self.value))
-            if isinstance(self.value, str):
-                return str(hashlib.sha256(self.value.encode()).hexdigest())
-            if isinstance(self.value, bytes):
-                return str(hashlib.sha256(self.value).hexdigest())
-            return str(hash(self.value))
+                return str(self.hash(value))
+            if isinstance(value, str):
+                return str(hashlib.sha256(value.encode()).hexdigest())
+            if isinstance(value, bytes):
+                return str(hashlib.sha256(value).hexdigest())
+            return str(hash(value))
         return "0"

src/_pytask/path.py

@@ -68,12 +68,6 @@ def find_closest_ancestor(path: Path, potential_ancestors: Sequence[Path]) -> Pa
     return sorted(potential_closest_ancestors, key=lambda x: len(x.parts))[-1]
 
 
-def find_common_ancestor_of_nodes(*names: str) -> Path:
-    """Find the common ancestor from task names and nodes."""
-    cleaned_names = [Path(name.split("::")[0]) for name in names]
-    return find_common_ancestor(*cleaned_names)
-
-
 def find_common_ancestor(*paths: Path) -> Path:
     """Find a common ancestor of many paths."""
     return Path(os.path.commonpath(paths))

src/_pytask/typing.py

@@ -1,9 +1,16 @@
 from __future__ import annotations
 
 import functools
+from enum import Enum
 from typing import Any
+from typing import Final
+from typing import Literal
+from typing import TYPE_CHECKING
 
-from attr import define
+from attrs import define
+
+if TYPE_CHECKING:
+    from typing_extensions import TypeAlias
 
 
 __all__ = ["Product", "ProductType"]
@@ -18,7 +25,29 @@ class ProductType:
 """ProductType: A singleton to mark products in annotations."""
 
 
-def is_task_function(func: Any) -> bool:
-    return (callable(func) and hasattr(func, "__name__")) or (
-        isinstance(func, functools.partial) and hasattr(func.func, "__name__")
+def is_task_function(obj: Any) -> bool:
+    """Check if an object is a task function."""
+    return (callable(obj) and hasattr(obj, "__name__")) or (
+        isinstance(obj, functools.partial) and hasattr(obj.func, "__name__")
     )
+
+
+class _NoDefault(Enum):
+    """A singleton for no defaults.
+
+    We make this an Enum
+    1) because it round-trips through pickle correctly (see GH#40397)
+    2) because mypy does not understand singletons
+
+    """
+
+    no_default = "NO_DEFAULT"
+
+    def __repr__(self) -> str:
+        return "<no_default>"
+
+
+no_default: Final = _NoDefault.no_default
+"""The value for missing defaults."""
+NoDefault: TypeAlias = Literal[_NoDefault.no_default]
+"""The type annotation."""

tests/test_execute.py

@@ -714,10 +714,8 @@ def test_execute_tasks_and_pass_values_only_by_python_nodes(runner, tmp_path):
     from typing_extensions import Annotated
     from pathlib import Path
 
-
     node_text = PythonNode(name="text")
 
-
     def task_create_text() -> Annotated[int, node_text]:
         return "This is the text."
 
@@ -743,21 +741,21 @@ def test_execute_tasks_via_functional_api(tmp_path):
     from pathlib import Path
 
 
-    node_text = PythonNode(name="text", hash=True)
+    node_text = PythonNode()
 
     def create_text() -> Annotated[int, node_text]:
         return "This is the text."
 
     node_file = PathNode.from_path(Path(__file__).parent.joinpath("file.txt"))
 
-    def create_file(text: Annotated[int, node_text]) -> Annotated[str, node_file]:
-        return text
+    def create_file(content: Annotated[str, node_text]) -> Annotated[str, node_file]:
+        return content
 
     if __name__ == "__main__":
         session = pytask.build(tasks=[create_file, create_text])
 
         assert len(session.tasks) == 2
-        assert len(session.dag.nodes) == 4
+        assert len(session.dag.nodes) == 5
     """
     tmp_path.joinpath("task_module.py").write_text(textwrap.dedent(source))
     result = subprocess.run(