FIX: modify isospin in create_particle() (#216)

* MAINT: test if `isospin` is correctly modified
ComPWA · Apr 6, 2023 · 09c7fd2 · 09c7fd2
1 parent 68fa240
commit 09c7fd2
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Showing 2 changed files with 17 additions and 3 deletions.
diff --git a/src/qrules/particle.py b/src/qrules/particle.py
@@ -464,9 +464,7 @@ def create_particle(  # pylint: disable=too-many-arguments,too-many-locals
             if tau_lepton_number
             else template_particle.tau_lepton_number
         ),
-        isospin=(
-            template_particle.isospin if isospin is None else template_particle.isospin
-        ),
+        isospin=template_particle.isospin if isospin is None else isospin,
         parity=template_particle.parity if parity is None else Parity(parity),
         c_parity=template_particle.c_parity if c_parity is None else Parity(c_parity),
         g_parity=template_particle.g_parity if g_parity is None else Parity(g_parity),

diff --git a/tests/unit/test_particle.py b/tests/unit/test_particle.py
@@ -436,6 +436,22 @@ def test_create_particle(particle_database: ParticleCollection, particle_name: s
     assert new_particle.strangeness == template_particle.strangeness
 
 
+def test_create_particle_isospin():
+    template_particle = Particle(
+        name="some particle",
+        pid=0,
+        spin=0,
+        mass=3.14,
+    )
+    new_isospin = Spin(0, 0)
+    new_particle = create_particle(
+        template_particle,
+        isospin=new_isospin,
+    )
+    assert template_particle.isospin != new_isospin
+    assert new_particle.isospin == new_isospin
+
+
 def test_get_name_root(particle_database: ParticleCollection):
     name_roots = {_get_name_root(p.name) for p in particle_database}
     assert name_roots == {