feat: add method to list leaf nodes

src/sciline/pipeline.py

@@ -5,9 +5,10 @@
 from collections.abc import Callable, Hashable, Iterable, Sequence
 from itertools import chain
 from types import UnionType
-from typing import TYPE_CHECKING, Any, TypeVar, get_args, get_type_hints, overload
+from typing import TYPE_CHECKING, Any, TypeVar, cast, get_args, get_type_hints, overload
 
 from ._provider import Provider, ToProvider
+from ._utils import key_name
 from .data_graph import DataGraph, to_task_graph
 from .display import pipeline_html_repr
 from .handler import ErrorHandler, HandleAsComputeTimeException
@@ -89,7 +90,9 @@ def compute(self, tp: type | Iterable[type] | UnionType, **kwargs: Any) -> Any:
         """
         return self.get(tp, **kwargs).compute()
 
-    def visualize(self, tp: type | Iterable[type], **kwargs: Any) -> graphviz.Digraph:
+    def visualize(
+        self, tp: type | Iterable[type] | None = None, **kwargs: Any
+    ) -> graphviz.Digraph:
         """
         Return a graphviz Digraph object representing the graph for the given keys.
 
@@ -103,6 +106,8 @@ def visualize(self, tp: type | Iterable[type], **kwargs: Any) -> graphviz.Digrap
         kwargs:
             Keyword arguments passed to :py:class:`graphviz.Digraph`.
         """
+        if tp is None:
+            tp = self.leafs()
         return self.get(tp, handler=HandleAsComputeTimeException()).visualize(**kwargs)
 
     def get(
@@ -200,6 +205,15 @@ def _repr_html_(self) -> str:
         nodes = ((key, data) for key, data in self.underlying_graph.nodes.items())
         return pipeline_html_repr(nodes)
 
+    def leafs(self) -> tuple[type, ...]:
+        """Returns the keys that are not inputs to any other providers."""
+        sink_nodes = [
+            cast(type, node)
+            for node, degree in self.underlying_graph.out_degree
+            if degree == 0
+        ]
+        return tuple(sorted(sink_nodes, key=key_name))
+
 
 def get_mapped_node_names(
     graph: DataGraph, base_name: type, *, index_names: Sequence[Hashable] | None = None

tests/pipeline_test.py

@@ -1414,3 +1414,13 @@ def bad(x: int, y: int) -> float:
     pipeline = sl.Pipeline()
     with pytest.raises(ValueError, match="Duplicate type hints"):
         pipeline.insert(bad)
+
+
+def test_leafs_method() -> None:
+    def make_float() -> float:
+        return 1.0
+
+    def make_str(x: int) -> str:
+        return "a string"
+
+    assert sl.Pipeline([make_float, make_str]).leafs() == (float, str)

tests/visualize_test.py

@@ -40,3 +40,11 @@ class SubA(A[T]):
     assert sl.visualize._format_type(A[float]).name == 'A[float]'
     assert sl.visualize._format_type(SubA[float]).name == 'SubA[float]'
     assert sl.visualize._format_type(B[float]).name == 'B[float]'
+
+
+def test_can_visualize_graph_without_explicit_target() -> None:
+    def int_to_float(x: int) -> float:
+        return float(x)
+
+    pipeline = sl.Pipeline([int_to_float])
+    pipeline.visualize()