From 29a5d43d77e505207902b2eb580f13925763f711 Mon Sep 17 00:00:00 2001
From: Leon Schittek <leon.schittek@gmx.net>
Date: Fri, 10 Mar 2023 11:24:37 +0100
Subject: [PATCH 1/2] Fix #105601: Remove duplicates when inserting links into
 multi inputs

Fix a regression that allowed to create several links between an
output socket and a multi input socket.

This regression was caused by commit 89aae4ac82.
---
 .../editors/space_node/node_relationships.cc  | 47 +++++++++++++------
 1 file changed, 33 insertions(+), 14 deletions(-)

diff --git a/source/blender/editors/space_node/node_relationships.cc b/source/blender/editors/space_node/node_relationships.cc
index 97ab6b7786c..c156fa82a2f 100644
--- a/source/blender/editors/space_node/node_relationships.cc
+++ b/source/blender/editors/space_node/node_relationships.cc
@@ -918,6 +918,8 @@ static void displace_links(bNodeTree *ntree, const bNode *node, bNodeLink *inser
         BKE_ntree_update_tag_link_changed(ntree);
         return;
       }
+      const int multi_input_index = node_socket_count_links(*ntree, *replacement_socket) - 1;
+      displaced_link->multi_input_socket_index = multi_input_index;
     }
   }
 
@@ -976,29 +978,46 @@ static void node_remove_existing_links_if_needed(bNodeLinkDrag &nldrag, bNodeTre
 {
   bNodeSocket &linked_socket = *nldrag.hovered_socket;
 
-  const int link_count = node_socket_count_links(ntree, linked_socket);
+  int link_count = node_socket_count_links(ntree, linked_socket);
   const int link_limit = nodeSocketLinkLimit(&linked_socket);
+  Set<bNodeLink *> links_to_remove;
 
-  if (link_count < link_limit) {
-    return;
-  }
+  ntree.ensure_topology_cache();
 
-  if (linked_socket.is_input()) {
-    LISTBASE_FOREACH_MUTABLE (bNodeLink *, link, &ntree.links) {
-      if (link->tosock == &linked_socket) {
-        nodeRemLink(&ntree, link);
-        return;
+  /* Remove duplicate links first. */
+  for (const bNodeLink dragged_link : nldrag.links) {
+    if (linked_socket.is_input()) {
+      for (bNodeLink *link : linked_socket.runtime->directly_linked_links) {
+        const bool duplicate_link = link->fromsock == dragged_link.fromsock;
+        if (duplicate_link) {
+          links_to_remove.add(link);
+          link_count--;
+        }
+      }
+    }
+    else {
+      for (bNodeLink *link : linked_socket.runtime->directly_linked_links) {
+        const bool duplicate_link = link->tosock == dragged_link.tosock;
+        if (duplicate_link) {
+          links_to_remove.add(link);
+          link_count--;
+        }
       }
     }
   }
-  else {
-    LISTBASE_FOREACH_MUTABLE (bNodeLink *, link, &ntree.links) {
-      if (link->fromsock == &linked_socket) {
-        nodeRemLink(&ntree, link);
-        return;
+
+  for (bNodeLink *link : linked_socket.runtime->directly_linked_links) {
+    const bool link_limit_exceeded = !(link_count < link_limit);
+    if (link_limit_exceeded) {
+      if (links_to_remove.add(link)) {
+        link_count--;
       }
     }
   }
+
+  for (bNodeLink *link : links_to_remove) {
+    nodeRemLink(&ntree, link);
+  }
 }
 
 static void add_dragged_links_to_tree(bContext &C, bNodeLinkDrag &nldrag)
-- 
2.30.2


From 56dc1bbdc1201dc855b1f22bbc59143c5105e5ee Mon Sep 17 00:00:00 2001
From: Leon Schittek <leon.schittek@gmx.net>
Date: Fri, 10 Mar 2023 11:31:30 +0100
Subject: [PATCH 2/2] Fix: Node Editor: Remove duplicate links when swapping
 links

Remove duplicate links when reconnecting displaced links into multi
input socket nodes.
This edge case wasn't handled when the feature was introduced in
commit 89aae4ac82.
---
 .../editors/space_node/node_relationships.cc  | 30 ++++++++++---------
 1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/source/blender/editors/space_node/node_relationships.cc b/source/blender/editors/space_node/node_relationships.cc
index c156fa82a2f..6cd0705a402 100644
--- a/source/blender/editors/space_node/node_relationships.cc
+++ b/source/blender/editors/space_node/node_relationships.cc
@@ -898,29 +898,31 @@ static void displace_links(bNodeTree *ntree, const bNode *node, bNodeLink *inser
   bNodeSocket *replacement_socket = node_find_linkable_socket(*ntree, node, linked_socket);
 
   if (linked_socket->is_input()) {
-    if (linked_socket->limit + 1 < nodeSocketLinkLimit(linked_socket)) {
+    BLI_assert(!linked_socket->is_multi_input());
+    ntree->ensure_topology_cache();
+    bNodeLink *displaced_link = linked_socket->runtime->directly_linked_links.first();
+
+    if (!replacement_socket) {
+      nodeRemLink(ntree, displaced_link);
       return;
     }
 
-    LISTBASE_FOREACH_MUTABLE (bNodeLink *, link, &ntree->links) {
-      if (link->tosock == linked_socket) {
-        if (!replacement_socket) {
-          nodeRemLink(ntree, link);
-          BKE_ntree_update_tag_link_removed(ntree);
+    displaced_link->tosock = replacement_socket;
+
+    if (replacement_socket->is_multi_input()) {
+      /* Check for duplicate links when linking to multi input sockets. */
+      for (bNodeLink *existing_link : replacement_socket->runtime->directly_linked_links) {
+        if (existing_link->fromsock == displaced_link->fromsock) {
+          nodeRemLink(ntree, displaced_link);
           return;
         }
-
-        link->tosock = replacement_socket;
-        if (replacement_socket->is_multi_input()) {
-          link->multi_input_socket_index = node_socket_count_links(*ntree, *replacement_socket) -
-                                           1;
-        }
-        BKE_ntree_update_tag_link_changed(ntree);
-        return;
       }
       const int multi_input_index = node_socket_count_links(*ntree, *replacement_socket) - 1;
       displaced_link->multi_input_socket_index = multi_input_index;
     }
+
+    BKE_ntree_update_tag_link_changed(ntree);
+    return;
   }
 
   LISTBASE_FOREACH_MUTABLE (bNodeLink *, link, &ntree->links) {
-- 
2.30.2