[bug] Fix issue with source position yaml loading

Author: OwenKephart

python_modules/dagster/dagster/_utils/yaml_utils.py

@@ -216,7 +216,10 @@ def construct_object(self, node: Any, deep: Any = False) -> ValueAndSourcePositi
                     Mapping[ValueAndSourcePositionTree, ValueAndSourcePositionTree], value
                 ).items():
                     dict_with_raw_values[k.value] = v.value
-                    child_trees[k.value] = v.source_position_tree
+                    child_trees[k.value] = SourcePositionTree(
+                        position=k.source_position_tree.position,
+                        children=v.source_position_tree.children,
+                    )
                 return ValueAndSourcePositionTree(
                     dict_with_raw_values,
                     SourcePositionTree(position=source_position, children=child_trees),

python_modules/dagster/dagster_tests/utils_tests/test_source_position.py

@@ -40,13 +40,13 @@ def visit(path: KeyPath, tree: SourcePositionTree):
     visit([], value_and_tree.source_position_tree)
     assert flattened == {
         "": "foo.yaml:2",
-        "foo": "foo.yaml:3",
+        "foo": "foo.yaml:2",
         "foo.bar": "foo.yaml:3",
         "foo.q": "foo.yaml:4",
         "foo.q.0": "foo.yaml:4",
         "foo.q.1": "foo.yaml:4",
         "foo.q.2": "foo.yaml:4",
-        "foo.baz": "foo.yaml:6",
+        "foo.baz": "foo.yaml:5",
         "foo.baz.0": "foo.yaml:6",
         "foo.baz.1": "foo.yaml:7",
         "foo.baz.1.b": "foo.yaml:7",
@@ -95,7 +95,7 @@ def __init__(self):
     populate_source_position_and_key_paths(value, parsed.source_position_tree)
     assert value.child.dicts[3][4]._source_position_and_key_path is not None  # noqa: SLF001
     assert (
-        str(value.child.dicts[3][4]._source_position_and_key_path.source_position) == "<string>:10"  # noqa: SLF001
+        str(value.child.dicts[3][4]._source_position_and_key_path.source_position) == "<string>:9"  # noqa: SLF001
     )
     assert value.child.dicts[3][4]._source_position_and_key_path.key_path == [  # noqa: SLF001
         "child",