chore: write tests for old syntax and specify future release deprecation

Author: zmx27

src/extensions/wrap_ScatteringFactorTable.cpp

@@ -160,7 +160,7 @@ Set internal ScatteringFactorTable according to specified string type.\n\
 tp   -- string identifier of a registered ScatteringFactorTable type.\n\
     Use ScatteringFactorTable.getRegisteredTypes for the allowed values.\n\
 \n\
-Deprecated: This method is deprecated and will be removed in a future release.\n\
+Deprecated: This method is deprecated and will be removed in the 2.0.0 release.\n\
 Use direct assignment to the `scatteringfactortable` property instead, for example:\n\
     obj.scatteringfactortable = SFTNeutron()\n\
 No return value.\n\
@@ -414,7 +414,8 @@ void wrap_ScatteringFactorTable()
                 bp::object DeprecationWarning = builtins.attr("DeprecationWarning");
                 warnings.attr("warn")(
                     std::string("setScatteringFactorTableByType is deprecated; "
-                            "assign the 'scatteringfactortable' property directly (for example, use SFTNeutron()/SFTXray())."),
+                            "assign the 'scatteringfactortable' property directly, for example:\n"
+                            "obj.scatteringfactortable = SFTNeutron()"),
                     DeprecationWarning,
                     2);
                 }

tests/test_debyepdfcalculator.py

@@ -5,11 +5,13 @@
 
 import pickle
 import unittest
+import warnings
 
 import numpy
 from testutils import _maxNormDiff, loadDiffPyStructure, pickle_with_attr
 
 from diffpy.srreal.pdfcalculator import DebyePDFCalculator, PDFCalculator
+from diffpy.srreal.scatteringfactortable import SFTNeutron
 
 
 ##############################################################################
@@ -141,6 +143,25 @@ def test_partial_pdfs(self):
 
     def test_pickling(self):
         """Check pickling and unpickling of PDFCalculator."""
+        # New syntax: assign an SFT instance to the property (should not warn)
+        dpdfc = self.dpdfc
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            dpdfc.scatteringfactortable = SFTNeutron()
+        self.assertFalse(
+            any(isinstance(x.message, DeprecationWarning) for x in w)
+        )
+
+        dpdfc.scatteringfactortable.setCustomAs("Na", "Na", 7)
+        spkl = pickle.dumps(dpdfc)
+        dpdfc1_new = pickle.loads(spkl)
+        self.assertEqual(
+            dpdfc.scatteringfactortable.type(),
+            dpdfc1_new.scatteringfactortable.type(),
+        )
+        self.assertEqual(7.0, dpdfc1_new.scatteringfactortable.lookup("Na"))
+
+        # Old syntax: call the deprecated method (should warn)
         dpdfc = self.dpdfc
         with self.assertWarns(DeprecationWarning):
             dpdfc.setScatteringFactorTableByType("N")