Update has_children functionality

docs/reference/ni-data-store-v2.md

@@ -57,6 +57,12 @@ extensions as dictionaries. Queries accept an OData expression and optional
 `MeasurementField`, for example `read_fields=[StepField.CONDITIONS]`; field names
 as strings are also accepted.
 
+`Step.has_children` is output-only and can be requested with
+`read_fields=[StepField.HAS_CHILDREN]`. It becomes true after the step has had a
+committed direct child and remains true even if that child is later deleted.
+The installed V2 proto package must include the field for its value to be read;
+older generated packages report it as false.
+
 Updates change only the fields named in the protobuf update mask, and the client
 builds the mask for you. Pass a `Step`, or its ID, with keyword fields, an update
 builder, or the whole object:

src/ni/datastore/data/v2/_types/_read_fields.py

@@ -72,6 +72,7 @@ class StepField(str, Enum):
     CONDITIONS = "conditions"
     MEASUREMENTS = "measurements"
     CHILDREN = "children"
+    HAS_CHILDREN = "has_children"
     TEST = "test"
 
 

src/ni/datastore/data/v2/_types/_step.py

@@ -58,6 +58,7 @@ class Step:
         "_children",
         "_path",
         "_path_ids",
+        "has_children",
         "created_at",
         "updated_at",
         "created_by",
@@ -125,6 +126,7 @@ def __init__(
         children: Iterable[Step] | None = None,
         path: Iterable[str] | None = None,
         path_ids: Iterable[str] | None = None,
+        has_children: bool = False,
         created_at: ht.datetime | None = None,
         updated_at: ht.datetime | None = None,
         created_by: str = "",
@@ -158,6 +160,7 @@ def __init__(
             children (optional): Child steps created with the step.
             path (optional): Output only. The step-name path, including this step.
             path_ids (optional): Output only. The step-identifier path, including this step.
+            has_children (optional): Output only. Whether this step has ever had a child step.
             created_at (optional): Output only. When the step was created.
             updated_at (optional): Output only. When the step was last updated.
             created_by (optional): Output only. Who created the step.
@@ -190,6 +193,7 @@ def __init__(
         self._children: MutableSequence[Step] = list(children) if children is not None else []
         self._path: MutableSequence[str] = string_list(path, "path")
         self._path_ids: MutableSequence[str] = string_list(path_ids, "path_ids")
+        self.has_children = has_children
         self.created_at = created_at
         self.updated_at = updated_at
         self.created_by = created_by
@@ -228,6 +232,7 @@ def from_protobuf(step_proto: StepProto) -> "Step":
             children=[Step.from_protobuf(child) for child in step_proto.children],
             path=step_proto.path,
             path_ids=step_proto.path_ids,
+            has_children=getattr(step_proto, "has_children", False),
             created_at=timestamp_from_protobuf(step_proto, "created_at"),
             updated_at=timestamp_from_protobuf(step_proto, "updated_at"),
             created_by=step_proto.created_by,
@@ -293,6 +298,7 @@ def __eq__(self, other: object) -> bool:
             and self.children == other.children
             and self.path == other.path
             and self.path_ids == other.path_ids
+            and self.has_children == other.has_children
             and self.created_at == other.created_at
             and self.updated_at == other.updated_at
             and self.created_by == other.created_by

tests/unit/data/test_v2_data_store_client.py

@@ -1225,9 +1225,15 @@ def test___get_step___sends_read_field_enums_as_field_names(
 ) -> None:
     service_client.get_step.return_value = data_store_pb2.Step(id="step-id")
 
-    client.get_step("step-id", read_fields=[StepField.NAME, StepField.CONDITIONS])
+    client.get_step(
+        "step-id", read_fields=[StepField.NAME, StepField.CONDITIONS, StepField.HAS_CHILDREN]
+    )
 
-    assert list(_sent(service_client.get_step).read_mask.paths) == ["name", "conditions"]
+    assert list(_sent(service_client.get_step).read_mask.paths) == [
+        "name",
+        "conditions",
+        "has_children",
+    ]
 
 
 def test___query_measurements___accepts_read_field_enums_and_plain_names(

tests/unit/data/test_v2_types.py

@@ -7,7 +7,7 @@
 import uuid
 from collections.abc import Callable
 from enum import Enum
-from typing import Any
+from typing import Any, cast
 
 import pytest
 from google.protobuf import json_format
@@ -137,6 +137,34 @@ def test___step___round_trips_through_protobuf_including_conditions() -> None:
     assert Step.from_protobuf(proto) == step
 
 
+def test___step___reads_has_children_from_protobuf() -> None:
+    class StepProtoWithHasChildren:
+        def __init__(self, step_proto: data_store_pb2.Step) -> None:
+            self._step_proto = step_proto
+
+        def __getattr__(self, name: str) -> Any:
+            if name == "has_children":
+                return True
+            return getattr(self._step_proto, name)
+
+    proto = cast(
+        data_store_pb2.Step,
+        StepProtoWithHasChildren(data_store_pb2.Step(name="parent")),
+    )
+
+    step = Step.from_protobuf(proto)
+
+    assert step.has_children is True
+
+
+def test___step___does_not_write_has_children_to_protobuf() -> None:
+    step = Step("parent", has_children=True)
+
+    proto = step.to_protobuf()
+
+    assert proto == data_store_pb2.Step(name="parent")
+
+
 def test___measurement___reads_metadata_and_conditions_from_protobuf() -> None:
     proto = data_store_pb2.Measurement(
         id="measurement-id",
@@ -340,8 +368,11 @@ def test___read_field_enums___match_protobuf_fields(
     field_type: type[Enum], message_type: Any
 ) -> None:
     field_names = sorted(field.value for field in field_type)
+    protobuf_field_names = sorted(field.name for field in message_type.DESCRIPTOR.fields)
+    if field_type is StepField and "has_children" not in protobuf_field_names:
+        field_names.remove(StepField.HAS_CHILDREN.value)
 
-    assert field_names == sorted(field.name for field in message_type.DESCRIPTOR.fields)
+    assert field_names == protobuf_field_names
 
 
 @pytest.mark.parametrize(
@@ -546,7 +577,14 @@ def test___client___wraps_every_low_level_method() -> None:
     assert sorted(low_level_methods - set(dir(DataStoreClient))) == []
 
 
-_OUTPUT_ONLY_INIT_PARAMETERS = {"id", "created_at", "updated_at", "created_by", "updated_by"}
+_OUTPUT_ONLY_INIT_PARAMETERS = {
+    "id",
+    "created_at",
+    "updated_at",
+    "created_by",
+    "updated_by",
+    "has_children",
+}
 
 
 @pytest.mark.parametrize(