dir() on a CPython struct lists its fields and methods

binding/emit_c_cpython.py

@@ -357,6 +357,29 @@ def emit_c(ctx):
     .sq_ass_item = lvpy_struct_array_ass_item,
 };
 
+/* dir() on a struct instance: what object.__dir__ finds, plus the fields and
+ * methods the struct's getattro resolves by name (lvgl-bindings#40). */
+static inline PyObject *lvpy_struct_dir(PyObject *self, const char *const *fields,
+    PyMethodDef *methods)
+{
+    PyObject *names = PyObject_CallMethod((PyObject *)&PyBaseObject_Type, "__dir__", "O", self);
+    if (names == NULL) return NULL;
+    PyObject *list = PySequence_List(names);
+    Py_DECREF(names);
+    if (list == NULL) return NULL;
+    for (; *fields != NULL; fields++) {
+        PyObject *s = PyUnicode_FromString(*fields);
+        if (s == NULL || PyList_Append(list, s) < 0) { Py_XDECREF(s); Py_DECREF(list); return NULL; }
+        Py_DECREF(s);
+    }
+    for (; methods->ml_name != NULL; methods++) {
+        PyObject *s = PyUnicode_FromString(methods->ml_name);
+        if (s == NULL || PyList_Append(list, s) < 0) { Py_XDECREF(s); Py_DECREF(list); return NULL; }
+        Py_DECREF(s);
+    }
+    return list;
+}
+
 static PyTypeObject lvpy_struct_array_type = {
     PyVarObject_HEAD_INIT(NULL, 0)
     .tp_name = "lvgl.StructArray",

binding/emit_cpython_native.py

@@ -2,6 +2,7 @@
 
 from __future__ import print_function
 
+import re
 import collections
 import copy
 from contextvars import ContextVar
@@ -475,6 +476,19 @@ def try_generate_struct_cpython(struct_name, struct):
     return PyObject_GenericGetAttr((PyObject *)self, name);
 }}
 
+static const char *const py_{san}_field_names[] = {{{field_names}NULL}};
+
+static PyObject *py_{san}_dir(PyObject *self, PyObject *unused)
+{{
+    (void)unused;
+    return lvpy_struct_dir(self, py_{san}_field_names, py_{san}_methods);
+}}
+
+static PyMethodDef py_{san}_type_methods[] = {{
+    {{"__dir__", py_{san}_dir, METH_NOARGS, NULL}},
+    {{NULL}}
+}};
+
 static int py_{san}_setattro(PyObject *self, PyObject *name, PyObject *value)
 {{
     if (value == NULL) {{
@@ -520,6 +534,7 @@ def try_generate_struct_cpython(struct_name, struct):
     .tp_getattro = (getter)py_{san}_getattro,
     .tp_setattro = (setter)py_{san}_setattro,
     .tp_new = py_{san}_new,
+    .tp_methods = py_{san}_type_methods,
     .tp_base = &py_lv_base_struct_type,
     .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
 }};
@@ -549,6 +564,12 @@ def try_generate_struct_cpython(struct_name, struct):
             san=sanitized_struct_name,
             struct_tag=struct_tag,
             read_cases="\n    ".join(read_cases) if read_cases else "(void)attr;",
+            field_names="".join(
+                '"%s", ' % name
+                for name in dict.fromkeys(
+                    re.findall(r'strcmp\(attr, "([^"]+)"\)', "".join(read_cases))
+                )
+            ),
             write_cases="\n    ".join(write_cases) if write_cases else "(void)value;",
             elem_size=elem_size_expr,
             # A conversion that fails has already stored its placeholder, so