fix StandardTransmuter.append_transformation promising list[bool] but returning nothing

fix brittle TestQuasiHarmonicDebyeApprox.test_gruneisen_parameter from tight assert_allclose abs tol

Author: janosh

src/pymatgen/alchemy/transmuters.py

@@ -103,7 +103,7 @@ def redo_next_change(self) -> None:
         for ts in self.transformed_structures:
             ts.redo_next_change()
 
-    def append_transformation(self, transformation, extend_collection=False, clear_redo=True):
+    def append_transformation(self, transformation, extend_collection=False, clear_redo=True) -> list[bool]:
         """Append a transformation to all TransformedStructures.
 
         Args:
@@ -117,8 +117,8 @@ def append_transformation(self, transformation, extend_collection=False, clear_r
                 redo, the redo list should not be cleared to allow multiple redos.
 
         Returns:
-            list[bool]: corresponding to initial transformed structures each boolean
-                describes whether the transformation altered the structure
+            list[bool]: Each list item is True if the transformation altered the structure
+                with the corresponding index.
         """
         if self.ncores and transformation.use_multiprocessing:
             with Pool(self.ncores) as pool:
@@ -136,6 +136,9 @@ def append_transformation(self, transformation, extend_collection=False, clear_r
                     new_structures += new
             self.transformed_structures += new_structures
 
+        # len(ts) > 1 checks if the structure has history
+        return [len(ts) > 1 for ts in self.transformed_structures]
+
     def extend_transformations(self, transformations):
         """Extend a sequence of transformations to the TransformedStructure.
 

tests/analysis/test_quasi_harmonic_debye_approx.py

@@ -193,7 +193,7 @@ def test_debye_temperature(self):
 
     def test_gruneisen_parameter(self):
         gamma = self.qhda.gruneisen_parameter(0, self.qhda.ev_eos_fit.v0)
-        assert_allclose(gamma, 2.188302, atol=1e-3)
+        assert_allclose(gamma, 2.188302, atol=1e-2)
 
     def test_thermal_conductivity(self):
         kappa = self.qhda.thermal_conductivity(self.T, self.opt_vol)