From d58ace926d87e3e2fdb253ad0935d5ffb4b89cb6 Mon Sep 17 00:00:00 2001
From: Sander Mertens <sander.mertens8@gmail.com>
Date: Mon, 7 Oct 2024 23:43:31 -0700
Subject: [PATCH] #1390 Fix issue with modified<R,T> where first type is a tag

---
 distr/flecs.h                       |  8 +++--
 include/flecs/addons/cpp/entity.hpp |  8 +++--
 test/cpp/project.json               |  4 ++-
 test/cpp/src/Pairs.cpp              | 47 +++++++++++++++++++++++++++++
 test/cpp/src/main.cpp               | 12 +++++++-
 5 files changed, 73 insertions(+), 6 deletions(-)

diff --git a/distr/flecs.h b/distr/flecs.h
index af48a9b005..11ae2c1aa1 100644
--- a/distr/flecs.h
+++ b/distr/flecs.h
@@ -25516,9 +25516,13 @@ struct entity : entity_builder<entity>
      * @tparam First The first part of the pair.
      * @tparam Second the second part of the pair.
      */
-    template <typename First, typename Second>
+    template <typename First, typename Second, typename A = actual_type_t<flecs::pair<First, Second>>>
     void modified() const {
-        this->modified<First>(_::type<Second>::id(world_));
+        auto first = _::type<First>::id(world_);
+        auto second = _::type<Second>::id(world_);
+        ecs_assert(_::type<A>::size() != 0, ECS_INVALID_PARAMETER,
+            "operation invalid for empty type");
+        this->modified(first, second);
     }
 
     /** Signal that the first part of a pair was modified.
diff --git a/include/flecs/addons/cpp/entity.hpp b/include/flecs/addons/cpp/entity.hpp
index 040b09f907..a8cce4dffa 100644
--- a/include/flecs/addons/cpp/entity.hpp
+++ b/include/flecs/addons/cpp/entity.hpp
@@ -191,9 +191,13 @@ struct entity : entity_builder<entity>
      * @tparam First The first part of the pair.
      * @tparam Second the second part of the pair.
      */
-    template <typename First, typename Second>
+    template <typename First, typename Second, typename A = actual_type_t<flecs::pair<First, Second>>>
     void modified() const {
-        this->modified<First>(_::type<Second>::id(world_));
+        auto first = _::type<First>::id(world_);
+        auto second = _::type<Second>::id(world_);
+        ecs_assert(_::type<A>::size() != 0, ECS_INVALID_PARAMETER,
+            "operation invalid for empty type");
+        this->modified(first, second);
     }
 
     /** Signal that the first part of a pair was modified.
diff --git a/test/cpp/project.json b/test/cpp/project.json
index bbea71e780..7d35c391a8 100644
--- a/test/cpp/project.json
+++ b/test/cpp/project.json
@@ -363,7 +363,9 @@
                 "deref_pair_obj",
                 "deref_const_pair_obj",
                 "set_R_existing_value",
-                "symmetric_w_childof"
+                "symmetric_w_childof",
+                "modified_tag_second",
+                "modified_tag_first"
             ]
         }, {
             "id": "Enum",
diff --git a/test/cpp/src/Pairs.cpp b/test/cpp/src/Pairs.cpp
index 160e06ed16..48694723e5 100644
--- a/test/cpp/src/Pairs.cpp
+++ b/test/cpp/src/Pairs.cpp
@@ -1253,3 +1253,50 @@ void Pairs_symmetric_w_childof(void) {
 
     test_assert(bob.has<Likes>(alice));
 }
+
+void Pairs_modified_tag_second(void) {
+    flecs::world ecs;
+
+    int32_t count = 0;
+    ecs.observer<Position>()
+        .term_at(0).second<Tag>()
+        .event(flecs::OnSet)
+        .each([&](Position& p) {
+            test_int(p.x, 10);
+            test_int(p.y, 20);
+            count ++;
+        });
+
+    flecs::entity e = ecs.entity();
+
+    Position& p = e.ensure<Position, Tag>();
+    p.x = 10;
+    p.y = 20;
+    e.modified<Position, Tag>();
+
+    test_int(count, 1);
+}
+
+void Pairs_modified_tag_first(void) {
+    flecs::world ecs;
+
+    int32_t count = 0;
+    ecs.observer()
+        .with<Tag, Position>()
+        .event(flecs::OnSet)
+        .each([&](flecs::iter& it, size_t row) {
+            auto p = it.field_at<Position>(0, row);
+            test_int(p.x, 10);
+            test_int(p.y, 20);
+            count ++;
+        });
+
+    flecs::entity e = ecs.entity();
+
+    Position& p = e.ensure<Tag, Position>();
+    p.x = 10;
+    p.y = 20;
+    e.modified<Tag, Position>();
+
+    test_int(count, 1);
+}
diff --git a/test/cpp/src/main.cpp b/test/cpp/src/main.cpp
index 1055236a1a..d1fdaf7e55 100644
--- a/test/cpp/src/main.cpp
+++ b/test/cpp/src/main.cpp
@@ -354,6 +354,8 @@ void Pairs_deref_pair_obj(void);
 void Pairs_deref_const_pair_obj(void);
 void Pairs_set_R_existing_value(void);
 void Pairs_symmetric_w_childof(void);
+void Pairs_modified_tag_second(void);
+void Pairs_modified_tag_first(void);
 
 // Testsuite 'Enum'
 void Enum_standard_enum_reflection(void);
@@ -2745,6 +2747,14 @@ bake_test_case Pairs_testcases[] = {
     {
         "symmetric_w_childof",
         Pairs_symmetric_w_childof
+    },
+    {
+        "modified_tag_second",
+        Pairs_modified_tag_second
+    },
+    {
+        "modified_tag_first",
+        Pairs_modified_tag_first
     }
 };
 
@@ -6739,7 +6749,7 @@ static bake_test_suite suites[] = {
         "Pairs",
         NULL,
         NULL,
-        68,
+        70,
         Pairs_testcases
     },
     {