From b1ce7a6715ed26e129ffc6da220d4bb3cc310422 Mon Sep 17 00:00:00 2001
From: Simon Heybrock <simon.heybrock@ess.eu>
Date: Wed, 4 Sep 2024 09:18:46 +0200
Subject: [PATCH] Fix transformation load for time-dependent value with sublogs

---
 src/scippnexus/nxtransformations.py |  6 +++++
 tests/nxtransformations_test.py     | 39 +++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/src/scippnexus/nxtransformations.py b/src/scippnexus/nxtransformations.py
index c0017f44..33e8146f 100644
--- a/src/scippnexus/nxtransformations.py
+++ b/src/scippnexus/nxtransformations.py
@@ -79,6 +79,12 @@ def make_transformation(
         select: ScippIndex,
     ):
         try:
+            if isinstance(value, sc.DataGroup) and (
+                isinstance(value.get('value'), sc.DataArray)
+            ):
+                # Some NXlog groups are split into value, alarm, and connection_status
+                # sublogs. We only care about the value.
+                value = value['value']
             if isinstance(value, sc.DataGroup):
                 return value
             t = value * self.vector
diff --git a/tests/nxtransformations_test.py b/tests/nxtransformations_test.py
index 5db5610c..e04135eb 100644
--- a/tests/nxtransformations_test.py
+++ b/tests/nxtransformations_test.py
@@ -197,6 +197,45 @@ def test_Transformation_with_multiple_values(h5root):
     assert_identical(detector[depends_on][()], expected)
 
 
+def test_time_dependent_transform_uses_value_sublog(h5root):
+    detector = create_detector(h5root)
+    snx.create_field(
+        detector, 'depends_on', sc.scalar('/detector_0/transformations/t1')
+    )
+    transformations = snx.create_class(detector, 'transformations', NXtransformations)
+    log = sc.DataArray(
+        sc.array(dims=['time'], values=[1.1, 2.2], unit='m'),
+        coords={'time': sc.array(dims=['time'], values=[11, 22], unit='s')},
+    )
+    log.coords['time'] = sc.epoch(unit='ns') + log.coords['time'].to(unit='ns')
+    offset = sc.spatial.translation(value=[1, 2, 3], unit='m')
+    vector = sc.vector(value=[0, 0, 1])
+    t = log * vector
+    t.data = sc.spatial.translations(dims=t.dims, values=t.values, unit=t.unit)
+    value = snx.create_class(transformations, 't1', snx.NXlog)
+    snx.create_field(value, 'time', log.coords['time'] - sc.epoch(unit='ns'))
+    snx.create_field(value, 'value', log.data)
+    # Add alarms with shorter time axis. This will trigger loading as a DataGroup with
+    # multiple contained DataArrays.
+    alarm = log['time', :2].copy()
+    alarm.coords['message'] = sc.array(dims=['time'], values=['alarm 1', 'alarm 2'])
+    snx.create_field(value, 'alarm_severity', alarm.data)
+    snx.create_field(value, 'alarm_message', alarm.coords['message'])
+    snx.create_field(value, 'alarm_time', alarm.coords['time'])
+    value.attrs['depends_on'] = '.'
+    value.attrs['transformation_type'] = 'translation'
+    value.attrs['offset'] = offset.values
+    value.attrs['offset_units'] = str(offset.unit)
+    value.attrs['vector'] = vector.value
+
+    expected = t * offset
+    expected.coords['depends_on'] = sc.scalar('.')
+    detector = make_group(detector)
+    depends_on = detector['depends_on'][()]
+    assert depends_on == 'transformations/t1'
+    assert_identical(detector[depends_on][()], expected)
+
+
 def test_chain_with_multiple_values(h5root):
     detector = create_detector(h5root)
     snx.create_field(