From 9680e852d6f7c580d409d763f8af73c858b1e729 Mon Sep 17 00:00:00 2001
From: Braden Dubois <braden.dubois@usask.ca>
Date: Wed, 8 Jan 2025 16:37:05 -0600
Subject: [PATCH 1/2] Added 'bind_set(...)' to std_binds

Based off github.com/beatmax's solution.
---
 include/pybind11/stl_bind.h | 76 +++++++++++++++++++++++++++++++++++++
 tests/test_stl_binders.cpp  |  4 ++
 tests/test_stl_binders.py   | 23 +++++++++++
 3 files changed, 103 insertions(+)

diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index af3a47f39c..cc6dd574b6 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -569,6 +569,82 @@ class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, A
     return cl;
 }
 
+//
+// std::set
+//
+template <typename Set, typename holder_type = std::unique_ptr<Set>, typename... Args>
+class_<Set, holder_type> bind_set(handle scope, std::string const &name, Args &&...args) {
+    using Class_ = class_<Set, holder_type>;
+    using T = typename Set::value_type;
+    using ItType = typename Set::iterator;
+
+    auto vtype_info = detail::get_type_info(typeid(T));
+    bool local = !vtype_info || vtype_info->module_local;
+
+    Class_ cl(scope, name.c_str(), pybind11::module_local(local), std::forward<Args>(args)...);
+    cl.def(init<>());
+    cl.def(init<const Set &>(), "Copy constructor");
+    cl.def(init([](iterable it) {
+        auto s = std::unique_ptr<Set>(new Set());
+        for (handle h : it)
+            s->insert(h.cast<T>());
+        return s.release();
+    }));
+    cl.def(self == self);
+    cl.def(self != self);
+    cl.def(
+        "remove",
+        [](Set &s, const T &x) {
+            auto p = s.find(x);
+            if (p != s.end())
+                s.erase(p);
+            else
+                throw value_error();
+        },
+        arg("x"),
+        "Remove the item from the set whose value is x. "
+        "It is an error if there is no such item.");
+    cl.def(
+        "__contains__",
+        [](const Set &s, const T &x) { return s.find(x) != s.end(); },
+        arg("x"),
+        "Return true if the container contains ``x``.");
+    cl.def(
+        "add",
+        [](Set &s, const T &value) { s.insert(value); },
+        arg("x"),
+        "Add an item to the set.");
+    cl.def("clear", [](Set &s) { s.clear(); }, "Clear the contents.");
+    cl.def(
+        "__iter__",
+        [](Set &s) {
+            return make_iterator<return_value_policy::copy, ItType, ItType, T>(s.begin(), s.end());
+        },
+        keep_alive<0, 1>() /* Essential: keep set alive while iterator exists */
+    );
+    cl.def(
+        "__repr__",
+        [name](Set &s) {
+            std::ostringstream os;
+            os << name << '{';
+            for (auto it = s.begin(); it != s.end(); ++it) {
+                if (it != s.begin())
+                    os << ", ";
+                os << *it;
+            }
+            os << '}';
+            return os.str();
+        },
+        "Return the canonical string representation of this set.");
+    cl.def(
+        "__bool__",
+        [](const Set &s) -> bool { return !s.empty(); },
+        "Check whether the set is nonempty");
+    cl.def("__len__", &Set::size);
+
+    return cl;
+}
+
 //
 // std::map, std::unordered_map
 //
diff --git a/tests/test_stl_binders.cpp b/tests/test_stl_binders.cpp
index f846ae8482..583b605d30 100644
--- a/tests/test_stl_binders.cpp
+++ b/tests/test_stl_binders.cpp
@@ -14,6 +14,7 @@
 
 #include <deque>
 #include <map>
+#include <set>
 #include <unordered_map>
 #include <vector>
 
@@ -183,6 +184,9 @@ TEST_SUBMODULE(stl_binders, m) {
     py::bind_vector<std::vector<El>>(m, "VectorEl");
     py::bind_vector<std::vector<std::vector<El>>>(m, "VectorVectorEl");
 
+    // test_set_int
+    py::bind_set<std::set<int>>(m, "SetInt");
+
     // test_map_string_double
     py::bind_map<std::map<std::string, double>>(m, "MapStringDouble");
     py::bind_map<std::unordered_map<std::string, double>>(m, "UnorderedMapStringDouble");
diff --git a/tests/test_stl_binders.py b/tests/test_stl_binders.py
index 9856ba462b..470bcf2091 100644
--- a/tests/test_stl_binders.py
+++ b/tests/test_stl_binders.py
@@ -149,6 +149,29 @@ def test_vector_custom():
     assert str(vv_b) == "VectorEl[El{1}, El{2}]"
 
 
+def test_set_int():
+    s_a = m.SetInt()
+    s_b = m.SetInt()
+
+    assert len(s_a) == 0
+    assert s_a == s_b
+
+    s_a.add(1)
+
+    assert 1 in s_a
+    assert str(s_a) == "SetInt{1}"
+    assert s_a != s_b
+
+    for i in range(5):
+        s_a.add(i)
+
+    assert sorted(s_a) == [0, 1, 2, 3, 4]
+
+    s_a.clear()
+    assert len(s_a) == 0
+    assert str(s_a) == "SetInt{}"
+
+
 def test_map_string_double():
     mm = m.MapStringDouble()
     mm["a"] = 1

From 1742c2185ad5272d75b79b3cfcd2dcbda2bd5136 Mon Sep 17 00:00:00 2001
From: Braden Dubois <braden.dubois@usask.ca>
Date: Thu, 9 Jan 2025 09:31:01 -0600
Subject: [PATCH 2/2] reworked test

---
 tests/test_stl_binders.cpp | 2 ++
 tests/test_stl_binders.py  | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/tests/test_stl_binders.cpp b/tests/test_stl_binders.cpp
index 583b605d30..ea3ccf5397 100644
--- a/tests/test_stl_binders.cpp
+++ b/tests/test_stl_binders.cpp
@@ -7,6 +7,7 @@
     BSD-style license that can be found in the LICENSE file.
 */
 
+#include <pybind11/attr.h>
 #include <pybind11/numpy.h>
 #include <pybind11/stl_bind.h>
 
@@ -186,6 +187,7 @@ TEST_SUBMODULE(stl_binders, m) {
 
     // test_set_int
     py::bind_set<std::set<int>>(m, "SetInt");
+    // py::implicitly_convertible<py::set, std::set<int>>();
 
     // test_map_string_double
     py::bind_map<std::map<std::string, double>>(m, "MapStringDouble");
diff --git a/tests/test_stl_binders.py b/tests/test_stl_binders.py
index 470bcf2091..50629d4956 100644
--- a/tests/test_stl_binders.py
+++ b/tests/test_stl_binders.py
@@ -153,12 +153,12 @@ def test_set_int():
     s_a = m.SetInt()
     s_b = m.SetInt()
 
-    assert len(s_a) == 0
     assert s_a == s_b
 
     s_a.add(1)
 
     assert 1 in s_a
+    assert len(s_a) == 1
     assert str(s_a) == "SetInt{1}"
     assert s_a != s_b