Feature: handle multi inheritance in C++

code-gen/src/poly_scribe_code_gen/cpp_gen.py

@@ -169,6 +169,14 @@ def _handle_rfl_tagged_union(parsed_idl: ParsedIDL) -> ParsedIDL:
     new_inheritance_data = {}
     for key in parsed_idl["inheritance_data"]:
         new_inheritance_data[f"{key}_t"] = parsed_idl["inheritance_data"][key]
+
+        # check if the values of the current key are also in the inheritance data and add their value to the new inheritance data as well
+        types_to_add = []
+        for value in parsed_idl["inheritance_data"][key]:
+            if value in parsed_idl["inheritance_data"]:
+                types_to_add.extend(parsed_idl["inheritance_data"][value])
+        new_inheritance_data[f"{key}_t"].extend(types_to_add)
+
         new_inheritance_data[f"{key}_t"].insert(0, key)
     parsed_idl["inheritance_data"] = new_inheritance_data
     return parsed_idl

code-gen/tests/cpp_gen_test.py

@@ -572,3 +572,68 @@ def test__render_template_boolean_default_value() -> None:
         struct_body = match[1]
         if match[0] == "Foo":
             assert "bool foo = true;".replace(" ", "") in struct_body.replace(" ", "")
+
+
+def test_render_template_struct_with_multi_inheritance() -> None:
+    idl = """
+dictionary X {
+    required int foo;
+};
+
+dictionary B : X {
+    required int bar;
+};
+
+dictionary C : X {
+    required float baz;
+};
+
+dictionary M : C {
+    required int qux;
+};
+
+dictionary N : C {
+    required int quux;
+};
+
+dictionary Y {
+    required N content;
+};
+"""
+    parsed_idl = _validate_and_parse(idl)
+
+    result = cpp_gen._render_template(parsed_idl, {"package": "test"})
+
+    pattern = re.compile(r"struct (\w+) \{([^}]*)\};", re.MULTILINE)
+    matches = pattern.findall(result)
+
+    assert len(matches) == 6
+    assert "X" in [match[0] for match in matches]
+    assert "B" in [match[0] for match in matches]
+    assert "C" in [match[0] for match in matches]
+    assert "Y" in [match[0] for match in matches]
+    assert "M" in [match[0] for match in matches]
+    assert "N" in [match[0] for match in matches]
+
+    for match in matches:
+        struct_body = match[1]
+        if match[0] == "X":
+            assert "int foo;".replace(" ", "") in struct_body.replace(" ", "")
+        elif match[0] == "B":
+            assert "int bar;".replace(" ", "") in struct_body.replace(" ", "")
+            assert "int foo;".replace(" ", "") in struct_body.replace(" ", "")
+        elif match[0] == "C":
+            assert "float baz;".replace(" ", "") in struct_body.replace(" ", "")
+            assert "int foo;".replace(" ", "") in struct_body.replace(" ", "")
+        elif match[0] == "M":
+            assert "int qux;".replace(" ", "") in struct_body.replace(" ", "")
+            assert "float baz;".replace(" ", "") in struct_body.replace(" ", "")
+            assert "int foo;".replace(" ", "") in struct_body.replace(" ", "")
+        elif match[0] == "N":
+            assert "int quux;".replace(" ", "") in struct_body.replace(" ", "")
+            assert "float baz;".replace(" ", "") in struct_body.replace(" ", "")
+            assert "int foo;".replace(" ", "") in struct_body.replace(" ", "")
+        elif match[0] == "Y":
+            assert "C_t content;".replace(" ", "") in struct_body.replace(" ", "")
+
+    assert 'using X_t = rfl::TaggedUnion<"type", X, B, C, M, N>;'.replace(" ", "") in result.replace(" ", "")