feat: display results in 'not found' error

src/sciline/pipeline.py

@@ -2,11 +2,14 @@
 # Copyright (c) 2023 Scipp contributors (https://github.com/scipp)
 from __future__ import annotations
 
+import re
 from collections.abc import Callable, Hashable, Iterable, Sequence
 from itertools import chain
 from types import UnionType
 from typing import TYPE_CHECKING, Any, TypeVar, cast, get_args, get_type_hints, overload
 
+from networkx import NetworkXError
+
 from ._provider import Provider, ToProvider
 from ._utils import key_name
 from .data_graph import DataGraph, to_task_graph
@@ -107,7 +110,7 @@ def visualize(
             Keyword arguments passed to :py:class:`graphviz.Digraph`.
         """
         if tp is None:
-            tp = self.leafs()
+            tp = self.final_result_keys()
         return self.get(tp, handler=HandleAsComputeTimeException()).visualize(**kwargs)
 
     def get(
@@ -140,7 +143,16 @@ def get(
             targets = tuple(keys)  # type: ignore[arg-type]
         else:
             targets = (keys,)  # type: ignore[assignment]
-        graph = to_task_graph(self, targets=targets, handler=handler)
+        try:
+            graph = to_task_graph(self, targets=targets, handler=handler)
+        except NetworkXError as e:
+            if re.match(r'^The node (.*) is not in the digraph.$', e.args[0]):
+                final_result_keys = ", ".join(map(repr, self.final_result_keys()))
+                raise KeyError(
+                    f'The requested type {e.__cause__} was not found in the pipeline. '
+                    f'Did you meant one of: {final_result_keys}?'
+                ) from e
+            raise e
         return TaskGraph(
             graph=graph,
             targets=targets if multi else keys,  # type: ignore[arg-type]
@@ -205,7 +217,7 @@ 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, ...]:
+    def final_result_keys(self) -> tuple[type, ...]:
         """Returns the keys that are not inputs to any other providers."""
         sink_nodes = [
             cast(type, node)

tests/pipeline_test.py

@@ -1416,11 +1416,11 @@ def bad(x: int, y: int) -> float:
         pipeline.insert(bad)
 
 
-def test_leafs_method() -> None:
+def test_final_result_keys_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)
+    assert sl.Pipeline([make_float, make_str]).final_result_keys() == (float, str)