Bug in opcConnectionImpl fix()

[Rutger Luyckx]

In the conn.fix() loop the conn.AutomationItems.Close() method causes the AutomationItems to be nil, this will result in the following panic:
panic: runtime error: invalid memory address or nil pointer dereference
@ line 396 in the conn.Tags() method and later @ line 322 in the conn.AutomationItems.Close() method when the first tryconnect was not successfull and it loops back. Maybe add a check to check if conn.AutomationItems != nil in these functions?

[Rutger Luyckx]

I was able to fix the issue. I rewrote the fix() method in connection_windows.go like this:

//fix tries to reconnect if connection is lost by creating a new connection
//with AutomationObject and creating a new AutomationItems instance.
func (conn *opcConnectionImpl) fix() {
	var err error
	var tags []string
	if !conn.IsConnected() {
		for {
			if conn.AutomationItems != nil {
				tags = conn.Tags()
				conn.AutomationItems.Close()
			}
			conn.AutomationItems, err = conn.TryConnect(conn.Server, conn.Nodes)
			if err != nil {
				logger.Println(err)
				time.Sleep(100 * time.Millisecond)
				continue
			}

			if conn.Add(tags...) == nil {
				logger.Printf("Added %d tags", len(tags))
			}
			break
		}
	}
}

[konimarti]

Thanks @Lynckx. Looks good! Could you also add a test to catch this in the future? Could you then submit a pull request so that I can merge it?

[Rutger Luyckx]

Made the pull request #15