Add distance coord to result data

src/tof/model.py

@@ -144,6 +144,7 @@ def run(self):
             container[c.name]['data'] = self.source.data.copy(deep=False)
             t = birth_time + (c.distance / speed).to(unit=birth_time.unit, copy=False)
             container[c.name]['data'].coords['toa'] = t
+            container[c.name]['data'].coords['distance'] = c.distance
             # TODO: remove 'tof' coordinate once deprecation period is over
             container[c.name]['data'].coords['tof'] = t
             if isinstance(c, Detector):

tests/model_test.py

@@ -355,3 +355,35 @@ def test_model_repr_does_not_raise():
         source=source, choppers=[chopper1, chopper2], detectors=[detector]
     )
     assert repr(model) is not None
+
+
+def test_component_distance():
+    # Make a chopper open from 10-20 ms. Assume zero phase.
+    topen = 10.0 * ms
+    tclose = 20.0 * ms
+    chopper = make_chopper(
+        topen=[topen],
+        tclose=[tclose],
+        f=10.0 * Hz,
+        phase=0.0 * deg,
+        distance=10 * meter,
+        name='chopper',
+    )
+    monitor = tof.Detector(distance=17 * meter, name='monitor')
+    detector = tof.Detector(distance=20 * meter, name='detector')
+
+    # Make a pulse with 3 neutrons with one neutron going through the chopper opening
+    # and the other two neutrons on either side of the opening.
+    source = make_source(
+        arrival_times=sc.concat(
+            [0.9 * topen, 0.5 * (topen + tclose), 1.1 * tclose], dim='event'
+        ),
+        distance=chopper.distance,
+    )
+
+    model = tof.Model(source=source, choppers=[chopper], detectors=[monitor, detector])
+    res = model.run()
+
+    assert sc.identical(res['monitor'].data.coords['distance'], monitor.distance)
+    assert sc.identical(res['detector'].data.coords['distance'], detector.distance)
+    assert sc.identical(res['chopper'].data.coords['distance'], chopper.distance)