Fix loading compounds from Madx for repeated element names

tests/test_compounds.py

@@ -161,6 +161,34 @@ def test_slicing_preserve_thick_compound_if_unsliced():
     ]
 
 
+def test_madloader_compounds_repeated_elements():
+    mad = Madx(stdout=False)
+    mad.options.rbarc = False
+    mad.input(f"""
+    mb: sbend, l:=1, angle:=0.1, k0:=0.2, k1=0.1;
+    ss: sequence, l:=2, refer=entry;
+        mb, at=0;
+        mb, at=1;
+    endsequence;
+    """)
+    mad.beam()
+    mad.use(sequence='ss')
+
+    line = xt.Line.from_madx_sequence(
+        sequence=mad.sequence.ss,
+        deferred_expressions=True,
+        allow_thick=True,
+    )
+
+    mb_compound_expected = ['mb_entry', 'mb_den', 'mb', 'mb_dex', 'mb_exit']
+    mb_compound_result = line.get_compound_subsequence('mb')
+    assert mb_compound_result == mb_compound_expected
+
+    mb0_compound_expected = ['mb_entry:0', 'mb_den:0', 'mb:0', 'mb_dex:0', 'mb_exit:0']
+    mb0_compound_result = line.get_compound_subsequence('mb:0')
+    assert mb0_compound_result == mb0_compound_expected
+
+
 @pytest.fixture(scope='function')
 def line_with_compounds(temp_context_default_func):
     # The fixture `temp_context_default_func` is defined in conftest.py and is

xtrack/mad_loader.py

@@ -318,6 +318,7 @@ def add_to_line(self, line, buffer):
         xtel = self.type(**self.attrs, _buffer=buffer)
         name = generate_repeated_name(line, self.name)
         line.append_element(xtel, name)
+        return name
 
 
 class ElementBuilderWithExpr(ElementBuilder):
@@ -329,7 +330,7 @@ def add_to_line(self, line, buffer):
         elref = line.element_refs[name]
         for k, p in self.attrs.items():
             set_expr(elref, k, p)
-        return xtel
+        return name
 
 
 class CompoundElementBuilder:
@@ -367,21 +368,24 @@ def add_to_line(self, line, buffer):
             [end_marker]
         )
 
+        new_name_map = {}
         for el in component_elements:
-            el.add_to_line(line, buffer)
+            added_name = el.add_to_line(line, buffer)
+            new_name_map[el.name] = added_name
 
         def _get_names(builder_elements):
-            return [elem.name for elem in builder_elements]
+            return [new_name_map[elem.name] for elem in builder_elements]
 
         compound = Compound(
             core=_get_names(self.core),
             aperture=_get_names(self.aperture),
             entry_transform=_get_names(self.entry_transform),
             exit_transform=_get_names(self.exit_transform),
-            entry=start_marker.name,
-            exit_=end_marker.name,
+            entry=new_name_map[start_marker.name],
+            exit_=new_name_map[end_marker.name],
         )
-        line.compound_container.define_compound(self.name, compound)
+        line.compound_container.define_compound(new_name_map[self.name], compound)
+        return list(new_name_map.values())
 
 
 class Aperture:
@@ -746,8 +750,8 @@ def add_elements(
     ):
         out = {}  # tbc
         for el in elements:
-            xt_element = el.add_to_line(line, buffer)
-            out[el.name] = xt_element  # tbc
+            name = el.add_to_line(line, buffer)
+            out[el.name] = name  # tbc
         return out  # tbc
 
     @property