nanobind: fix adapted ctor stub signature (remoe redundant self)

Author: pthom

src/litgen/internal/adapted_types/adapted_function.py

@@ -1207,7 +1207,15 @@ def _stub_params_list_signature(self) -> list[str]:
         cpp_adapted_function_terse = self.cpp_adapted_function.with_terse_types()
         cpp_parameters = cpp_adapted_function_terse.parameter_list.parameters
         r = []
-        for param in cpp_parameters:
+        for i, param in enumerate(cpp_parameters):
+            # For nanobind, skip first "self" argument in constructors
+            is_nanobind = self.options.bind_library == BindLibraryType.nanobind
+            if is_nanobind:
+                is_ctor = self.is_constructor()
+                is_first_self_arg = i == 0 and param.decl.decl_name == "self"
+                if is_ctor and is_first_self_arg:
+                    continue
+
             param_decl = param.decl
 
             param_name_python = cpp_to_python.var_name_to_python(self.options, param_decl.decl_name)

src/litgen/tests/internal/adapted_types/adapted_class_test.py

@@ -751,6 +751,34 @@ def test_numeric_array_member() -> None:
     )
 
 
+def test_nanobind_adapted_ctor_stub() -> None:
+    # The constructor params below will automatically be "adapted" into std::array<uint8_t, 4>
+    code = """
+    struct Color4
+    {
+        Color4(const uint8_t _rgba[4]);
+        uint8_t rgba[4];
+    };
+    """
+    options = litgen.LitgenOptions()
+    options.bind_library = BindLibraryType.nanobind
+    generated_code = litgen.generate_code(options, code)
+
+    # Below, we test that the ctor signature is adapted to accept List[int]
+    # (and does not specify an additional self parameter, cf AdaptedFunction.stub_params_list_signature())
+    # print(generated_code.stub_code)
+    code_utils.assert_are_codes_equal(
+        generated_code.stub_code,
+        """
+        class Color4:
+            def __init__(self, _rgba: List[int]) -> None:
+                pass
+            rgba: np.ndarray  # ndarray[type=uint8_t, size=4]
+        """
+    )
+
+
+
 def test_adapted_ctor() -> None:
     # The constructor for Color4 will be adapted to accept std::array<uint8_t, 4>
     code = """