fix: guard AddPowderPatternDiffraction setup

news/94.rst

@@ -0,0 +1,23 @@
+**Added:**
+
+* <news item>
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* Fixed `PowderPattern.AddPowderPatternDiffraction()` so a no-reflections failure does not leave a failed diffraction component attached to the powder pattern.
+
+**Security:**
+
+* <news item>

src/extensions/powderpattern_ext.cpp

@@ -24,6 +24,7 @@
 #include <boost/format.hpp>
 #undef B0
 
+#include <memory>
 #include <string>
 
 #include <ObjCryst/RefinableObj/RefinableObj.h>
@@ -39,7 +40,6 @@ using namespace ObjCryst;
 
 namespace {
 
-
 // This creates a C++ PowderPattern object
 PowderPattern* _CreatePowderPatternFromCIF(bp::object input)
 {
@@ -117,11 +117,30 @@ PowderPatternBackground& addppbackground(PowderPattern& pp)
 
 PowderPatternDiffraction& addppdiffraction(PowderPattern& pp, Crystal& crst)
 {
-    PowderPatternDiffraction* ppc = new PowderPatternDiffraction();
+    std::unique_ptr<PowderPatternDiffraction> ppc(new PowderPatternDiffraction());
     ppc->SetCrystal(crst);
+    // Prepare against the target powder-pattern context before final
+    // registration so a no-reflections failure cannot leave a broken
+    // partially attached component behind.
+    ppc->SetParentPowderPattern(pp);
+    ppc->GenHKLFullSpace();
+    if(ppc->GetNbReflBelowMaxSinThetaOvLambda() == 0)
+    {
+        throw ObjCrystException(
+            "PowderPatternDiffraction::CalcSinThetaLambda(): there are no reflections!"
+        );
+    }
     pp.AddPowderPatternComponent(*ppc);
-    pp.Prepare();
-    return *ppc;
+    try
+    {
+        pp.Prepare();
+    }
+    catch(...)
+    {
+        pp.RemovePowderPatternComponent(*ppc);
+        throw;
+    }
+    return *ppc.release();
 }
 
 

src/extensions/powderpatterndiffraction_ext.cpp

@@ -77,4 +77,5 @@ void wrap_powderpatterndiffraction()
         .def("GetFhklObsSq", &PowderPatternDiffraction::GetFhklObsSq,
                 return_value_policy<copy_const_reference>())
         ;
+
 }

tests/test_powderpattern.py

@@ -18,6 +18,7 @@
 
 import numpy as np
 import pytest
+from testutils import makeCrystal, makeScatterer
 
 from pyobjcryst import ObjCrystException
 from pyobjcryst.indexing import CrystalCentering, CrystalSystem, quick_index
@@ -74,6 +75,20 @@ def test_GetPowderPatternX(self):
         self.assertTrue(np.array_equal([], self.pp.GetPowderPatternX()))
         return
 
+    def test_AddPowderPatternDiffraction_rollback_on_prepare_error(self):
+        pp = self.pp
+        crystal = makeCrystal(*makeScatterer())
+        pp.SetWavelength(1.54056)
+        # Keep the 2theta window below the first reflection so setup raises
+        # and we can verify the failed diffraction component is not retained.
+        pp.SetPowderPatternPar(np.deg2rad(0.1), np.deg2rad(0.01), 41)
+
+        with self.assertRaisesRegex(ObjCrystException, "no reflections"):
+            pp.AddPowderPatternDiffraction(crystal)
+
+        self.assertEqual(0, pp.GetNbPowderPatternComponent())
+        return
+
     # def test_GetScaleFactor(self):  assert False
     # def test_ImportPowderPattern2ThetaObs(self):  assert False
     # def test_ImportPowderPattern2ThetaObsSigma(self):  assert False