Fix buffer deletion from a client when another is editing it

src/client_manager.cc

@@ -1,6 +1,7 @@
 #include "client_manager.hh"
 
 #include "event_manager.hh"
+#include "buffer_manager.hh"
 
 namespace Kakoune
 {
@@ -62,6 +63,28 @@ Window& ClientManager::get_unused_window_for_buffer(Buffer& buffer) const
     return buffer.new_window();
 }
 
+void ClientManager::ensure_no_client_uses_buffer(Buffer& buffer)
+{
+    for (auto& client : m_clients)
+    {
+        if (&client.context->buffer() != &buffer)
+            continue;
+
+        // change client context to edit the first buffer which is not the
+        // specified one. As BufferManager stores buffer according to last
+        // access, this selects a sensible buffer to display.
+        for (auto& buf : BufferManager::instance())
+        {
+            if (buf != &buffer)
+            {
+               Window& w = get_unused_window_for_buffer(*buf);
+               client.context->change_editor(w);
+               break;
+            }
+        }
+    }
+}
+
 void ClientManager::redraw_clients() const
 {
     for (auto& client : m_clients)

src/client_manager.hh

@@ -20,6 +20,7 @@ public:
     size_t count() const { return m_clients.size(); }
 
     Window& get_unused_window_for_buffer(Buffer& buffer) const;
+    void    ensure_no_client_uses_buffer(Buffer& buffer);
 
     void redraw_clients() const;
 private:

src/commands.cc

@@ -401,20 +401,10 @@ void delete_buffer(const CommandParameters& params, Context& context)
     if (buffer->type()!= Buffer::Type::Scratch and buffer->is_modified())
         throw runtime_error("buffer " + buffer->name() + " is modified");
 
-    if (&context.buffer() == buffer)
-    {
     if (manager.count() == 1)
         throw runtime_error("buffer " + buffer->name() + " is the last one");
-        for (auto& buf : manager)
+
-        {
+    ClientManager::instance().ensure_no_client_uses_buffer(*buffer);
-            if (buf != buffer)
-            {
-               Window& w = ClientManager::instance().get_unused_window_for_buffer(*buf);
-               context.change_editor(w);
-               break;
-            }
-        }
-    }
     delete buffer;
 }