Merge pull request #80 from scipp/nxcansas-bin-centers

Change SASdata to raise an error instead of writing invalid Q coord

docs/about/release-notes.rst

@@ -28,6 +28,19 @@ Release Notes
    Neil Vaytet :sup:`a`\ ,
    and Jan-Lukas Wynen :sup:`a`
 
+v0.4.2 (November 2022)
+----------------------
+
+Bugfixes
+~~~~~~~~
+
+* Fix SASdata to raise an exception when given Q-edges, which is not valid for SASdata `#77 <https://github.com/scipp/scippnexus/pull/77>`_.
+
+Contributors
+~~~~~~~~~~~~
+
+Simon Heybrock :sup:`a`
+
 v0.4.1 (November 2022)
 ----------------------
 

requirements-lowest/test-lowest.in

@@ -1,5 +1,5 @@
 python-dateutil
-scipp==0.12.4
+scipp==0.13.1
 scipy
 h5py
 pytest

requirements-lowest/test-lowest.txt

@@ -1,9 +1,8 @@
-# SHA1:f2d0f341978c4e9d11ba22dedb60abe2d5d75ded
 #
-# This file is autogenerated by pip-compile-multi
+# This file is autogenerated by pip-compile with python 3.8
 # To update, run:
 #
-#    pip-compile-multi
+#    pip-compile test-lowest.in
 #
 attrs==22.1.0
     # via pytest
@@ -14,7 +13,7 @@ exceptiongroup==1.0.0rc9
 graphlib-backport==1.0.3
     # via scipp
 h5py==3.7.0
-    # via -r requirements/test-lowest.in
+    # via -r test-lowest.in
 iniconfig==1.1.1
     # via pytest
 numpy==1.23.4
@@ -29,15 +28,15 @@ pluggy==1.0.0
 pyparsing==3.0.9
     # via packaging
 pytest==7.2.0
-    # via -r requirements/test-lowest.in
+    # via -r test-lowest.in
 python-dateutil==2.8.2
-    # via -r requirements/test-lowest.in
+    # via -r test-lowest.in
 pyyaml==6.0
     # via confuse
-scipp==0.12.4
-    # via -r requirements/test-lowest.in
+scipp==0.13.1
+    # via -r test-lowest.in
 scipy==1.9.3
-    # via -r requirements/test-lowest.in
+    # via -r test-lowest.in
 six==1.16.0
     # via python-dateutil
 tomli==2.0.1

src/scippnexus/definitions/nxcansas.py

@@ -59,6 +59,10 @@ def __write_to_nexus_group__(self, group: NXobject):
         if da.variances is not None:
             signal.attrs['uncertainties'] = 'I_errors'
             group.create_field('I_errors', sc.stddevs(da.data))
+        if da.coords.is_edges('Q'):
+            raise ValueError(
+                "Q is given as bin-edges, but NXcanSAS requires Q points (such as "
+                "bin centers).")
         coord = group.create_field('Q', da.coords['Q'])
         if da.coords['Q'].variances is not None:
             if self._variances is None:

tests/application_definition_test.py

@@ -6,7 +6,7 @@
 
 
 @pytest.fixture()
-def nxroot(request):
+def nxroot():
     """Yield NXroot containing a single NXentry named 'entry'"""
     with h5py.File('dummy.nxs', mode='w', driver="core", backing_store=False) as f:
         root = NXroot(f)
@@ -23,7 +23,8 @@ def test_setitem_SASentry(nxroot):
     assert entry['run'][()] == 12345
 
 
-def test_setitem_SASdata(nxroot):
+@pytest.fixture()
+def I_of_Q():
     data = sc.array(
         dims=['Q'],
         values=[0.1, 0.2, 0.1, 0.4],
@@ -32,10 +33,20 @@ def test_setitem_SASdata(nxroot):
     da = sc.DataArray(data=data)
     da.coords['Q'] = sc.linspace('Q', 0, 1, num=5, unit='1/angstrom')
     da.coords['Q'].variances = sc.array(dims=['Q'], values=[1, 1, 4, 4, 1]).values
-    nxroot['sasdata'] = SASdata(da, Q_variances='resolutions')
+    return da
+
+
+def test_setitem_SASdata_raises_ValueError_when_given_bin_edges(nxroot, I_of_Q):
+    with pytest.raises(ValueError):
+        nxroot['sasdata'] = SASdata(I_of_Q, Q_variances='resolutions')
+
+
+def test_setitem_SASdata(nxroot, I_of_Q):
+    I_of_Q.coords['Q'] = I_of_Q.coords['Q'][1:]
+    nxroot['sasdata'] = SASdata(I_of_Q, Q_variances='resolutions')
     nxroot._definition = NXcanSAS
     data = nxroot['sasdata']
-    assert sc.identical(data[...], da)
+    assert sc.identical(data[...], I_of_Q)
 
 
 def test_setitem_SASdata_raises_if_interpretation_of_variances_not_specified(nxroot):