From 37242f67e0189d5d1d1836a8ef918c7cd013719e Mon Sep 17 00:00:00 2001
From: Jon Evans <jon@craftyjon.com>
Date: Sun, 21 Mar 2021 15:31:15 -0400
Subject: [PATCH] Connectivity: just pick the most popular net to update
 conflicting clusters

CHANGED: when pad net assignments are changed in a conflicting way (i.e.,
         tracks exist that short out more than one net after the change,
         track nets will be updated to the net with the most pads).

Fixes https://gitlab.com/kicad/code/kicad/-/issues/7929
---
 pcbnew/connectivity/connectivity_algo.cpp  | 20 ++++++++--------
 pcbnew/connectivity/connectivity_items.cpp | 27 ++++++++++++++++++----
 pcbnew/connectivity/connectivity_items.h   |  9 ++++----
 3 files changed, 38 insertions(+), 18 deletions(-)

diff --git a/pcbnew/connectivity/connectivity_algo.cpp b/pcbnew/connectivity/connectivity_algo.cpp
index 3ed63ee4e5..e4fe163974 100644
--- a/pcbnew/connectivity/connectivity_algo.cpp
+++ b/pcbnew/connectivity/connectivity_algo.cpp
@@ -481,17 +481,19 @@ void CN_CONNECTIVITY_ALGO::propagateConnections( BOARD_COMMIT* aCommit )
 {
     for( const auto& cluster : m_connClusters )
     {
-        if( cluster->IsConflicting() )
+        if( cluster->IsOrphaned() )
         {
-            wxLogTrace( "CN", "Conflicting nets in cluster %p\n", cluster.get() );
-        }
-        else if( cluster->IsOrphaned() )
-        {
-            wxLogTrace( "CN", "Skipping orphaned cluster %p [net: %s]\n", cluster.get(),
+            wxLogTrace( "CN", "Skipping orphaned cluster %p [net: %s]", cluster.get(),
                     (const char*) cluster->OriginNetName().c_str() );
         }
         else if( cluster->HasValidNet() )
         {
+            if( cluster->IsConflicting() )
+            {
+                wxLogTrace( "CN", "Conflicting nets in cluster %p; chose %d (%s)", cluster.get(),
+                            cluster->OriginNet(), cluster->OriginNetName() );
+            }
+
             // normal cluster: just propagate from the pads
             int n_changed = 0;
 
@@ -515,15 +517,15 @@ void CN_CONNECTIVITY_ALGO::propagateConnections( BOARD_COMMIT* aCommit )
 
             if( n_changed )
             {
-                wxLogTrace( "CN", "Cluster %p : net : %d %s\n", cluster.get(),
+                wxLogTrace( "CN", "Cluster %p : net : %d %s", cluster.get(),
                         cluster->OriginNet(), (const char*) cluster->OriginNetName().c_str() );
             }
             else
-                wxLogTrace( "CN", "Cluster %p : nothing to propagate\n", cluster.get() );
+                wxLogTrace( "CN", "Cluster %p : nothing to propagate", cluster.get() );
         }
         else
         {
-            wxLogTrace( "CN", "Cluster %p : connected to unused net\n", cluster.get() );
+            wxLogTrace( "CN", "Cluster %p : connected to unused net", cluster.get() );
         }
     }
 }
diff --git a/pcbnew/connectivity/connectivity_items.cpp b/pcbnew/connectivity/connectivity_items.cpp
index 6190c9d479..0c168c321b 100644
--- a/pcbnew/connectivity/connectivity_items.cpp
+++ b/pcbnew/connectivity/connectivity_items.cpp
@@ -472,20 +472,37 @@ void CN_CLUSTER::Add( CN_ITEM* item )
 {
     m_items.push_back( item );
 
-    if( item->Net() <= 0 )
+    int netCode = item->Net();
+
+    if( netCode <= 0 )
         return;
 
     if( m_originNet <= 0 )
     {
-        m_originNet = item->Net();
+        m_originNet = netCode;
     }
 
     if( item->Parent()->Type() == PCB_PAD_T )
     {
-        if( !m_originPad )
+        if( m_netRanks.count( netCode ) )
         {
-            m_originPad = item;
-            m_originNet = item->Net();
+            m_netRanks[netCode]++;
+
+            if( m_netRanks.count( m_originNet ) && m_netRanks[netCode] > m_netRanks[m_originNet] )
+            {
+                m_originPad = item;
+                m_originNet = netCode;
+            }
+        }
+        else
+        {
+            m_netRanks[netCode] = 1;
+
+            if( !m_originPad )
+            {
+                m_originPad = item;
+                m_originNet = netCode;
+            }
         }
 
         if( m_originPad && item->Net() != m_originNet )
diff --git a/pcbnew/connectivity/connectivity_items.h b/pcbnew/connectivity/connectivity_items.h
index 82b733cedc..c036d398d6 100644
--- a/pcbnew/connectivity/connectivity_items.h
+++ b/pcbnew/connectivity/connectivity_items.h
@@ -451,10 +451,11 @@ private:
 class CN_CLUSTER
 {
 private:
-    bool                  m_conflicting;
-    int                   m_originNet;
-    CN_ITEM*              m_originPad;
-    std::vector<CN_ITEM*> m_items;
+    bool                         m_conflicting;
+    int                          m_originNet;
+    CN_ITEM*                     m_originPad;
+    std::vector<CN_ITEM*>        m_items;
+    std::unordered_map<int, int> m_netRanks;
 
 public:
     CN_CLUSTER();