feat(bindings): support scalar default wrapper generation

scripts/generate_wrappers.py

@@ -53,8 +53,10 @@ def _get_compilers():
         system_include_flags = _get_system_include_flags()
 
         index = clang.cindex.Index.create()
-        args = ("-std=c++17", "-x", "c++", "-I", "src") + tuple(system_include_flags)
-        translation_unit = index.parse(f"src/base/{op_name}.h", args=args)
+        args = ("-std=c++17", "-x", "c++", "-I", str(_SRC_DIR)) + tuple(
+            system_include_flags
+        )
+        translation_unit = index.parse(str(_BASE_DIR / f"{op_name}.h"), args=args)
 
         nodes = tuple(type(self)._find(translation_unit.cursor, op_name))
 
@@ -112,9 +114,31 @@ def _find_vector_tensor_params(op_name):
     return set(re.findall(r"std::vector<Tensor>\s+(\w+)", source))
 
 
+def _find_params_with_defaults(op_name):
+    """Return `{param_name: default_literal}` for scalar params with defaults.
+
+    `libclang`'s cursor API does not expose defaults reliably, so we regex-scan
+    the source. Only used for plain scalar defaults such as
+    `bool pre_gathered = false`.
+    """
+    source = (_BASE_DIR / f"{op_name}.h").read_text()
+
+    mapping = {}
+
+    for name, default in re.findall(
+        r"\b(?:bool|int(?:64_t|32_t|8_t|16_t)?|std::size_t|std::uint\w+_t|"
+        r"float|double)\s+(\w+)\s*=\s*([^,\)]+?)\s*(?:,|\))",
+        source,
+    ):
+        mapping[name] = default.strip()
+
+    return mapping
+
+
 def _generate_pybind11(operator):
     optional_tensor_params = _find_optional_tensor_params(operator.name)
     vector_tensor_params = _find_vector_tensor_params(operator.name)
+    params_with_defaults = _find_params_with_defaults(operator.name)
 
     def _is_optional_tensor(arg):
         if arg.spelling in optional_tensor_params:
@@ -186,6 +210,10 @@ def _generate_py_args(node):
 
             if _is_optional(arg):
                 parts.append(f'py::arg("{arg.spelling}") = py::none()')
+            elif arg.spelling in params_with_defaults:
+                parts.append(
+                    f'py::arg("{arg.spelling}") = {params_with_defaults[arg.spelling]}'
+                )
             else:
                 parts.append(f'py::arg("{arg.spelling}")')
 

tests/test_generate_wrappers.py

@@ -0,0 +1,114 @@
+import functools
+import importlib.util
+from pathlib import Path
+
+import pytest
+
+
+pytest.importorskip("clang.cindex")
+
+
+@functools.lru_cache(maxsize=1)
+def _load_generator():
+    script = Path(__file__).parents[1] / "scripts" / "generate_wrappers.py"
+    spec = importlib.util.spec_from_file_location("generate_wrappers", script)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+
+    return module
+
+
+def _generate_binding(op_name, tmp_path, monkeypatch, source):
+    generator = _load_generator()
+    src_dir = tmp_path / "src"
+    base_dir = src_dir / "base"
+    base_dir.mkdir(parents=True)
+    (base_dir / f"{op_name}.h").write_text(source)
+    monkeypatch.setattr(generator, "_SRC_DIR", src_dir)
+    monkeypatch.setattr(generator, "_BASE_DIR", base_dir)
+    operator = generator._OperatorExtractor()(op_name)
+
+    return generator._generate_pybind11(operator)
+
+
+def test_mha_varlen_fwd_requires_out_binding(tmp_path, monkeypatch):
+    text = _generate_binding(
+        "mha_varlen_fwd",
+        tmp_path,
+        monkeypatch,
+        """
+#include <cstdint>
+#include <optional>
+
+namespace infini::ops {
+
+struct Tensor {};
+
+template <typename T>
+class Operator {};
+
+class MhaVarlenFwd : public Operator<MhaVarlenFwd> {
+ public:
+  MhaVarlenFwd(const Tensor q, const Tensor k, const Tensor v, Tensor out,
+               const Tensor cu_seqlens_q, const Tensor cu_seqlens_k,
+               std::optional<Tensor> block_table, float softmax_scale,
+               bool is_causal, int64_t num_splits = 0) {}
+
+  virtual void operator()(const Tensor q, const Tensor k, const Tensor v,
+                          Tensor out, const Tensor cu_seqlens_q,
+                          const Tensor cu_seqlens_k,
+                          std::optional<Tensor> block_table,
+                          float softmax_scale, bool is_causal,
+                          int64_t num_splits = 0) const = 0;
+};
+
+}  // namespace infini::ops
+""",
+    )
+
+    assert 'py::arg("out"), py::arg("cu_seqlens_q")' in text
+    assert 'py::arg("num_splits") = 0' in text
+    assert 'py::arg("out") = py::none()' not in text
+    assert "std::optional<py::object> out" not in text
+    assert "OptionalTensorFromPybind11Handle(out)" not in text
+
+
+def test_mha_fwd_kvcache_requires_out_binding(tmp_path, monkeypatch):
+    text = _generate_binding(
+        "mha_fwd_kvcache",
+        tmp_path,
+        monkeypatch,
+        """
+#include <cstdint>
+#include <optional>
+
+namespace infini::ops {
+
+struct Tensor {};
+
+template <typename T>
+class Operator {};
+
+class MhaFwdKvcache : public Operator<MhaFwdKvcache> {
+ public:
+  MhaFwdKvcache(const Tensor q, const Tensor kcache, const Tensor vcache,
+                std::optional<Tensor> k, std::optional<Tensor> v, Tensor out,
+                float softmax_scale, bool is_causal,
+                int64_t num_splits = 0) {}
+
+  virtual void operator()(const Tensor q, const Tensor kcache,
+                          const Tensor vcache, std::optional<Tensor> k,
+                          std::optional<Tensor> v, Tensor out,
+                          float softmax_scale, bool is_causal,
+                          int64_t num_splits = 0) const = 0;
+};
+
+}  // namespace infini::ops
+""",
+    )
+
+    assert 'py::arg("out"), py::arg("softmax_scale")' in text
+    assert 'py::arg("num_splits") = 0' in text
+    assert 'py::arg("out") = py::none()' not in text
+    assert "std::optional<py::object> out" not in text
+    assert "OptionalTensorFromPybind11Handle(out)" not in text