Should notepad++ not be responding with a message other than “Please check if the file is open in another program” though?
yes, and it will, if you go to settings > preferences > default directory and activate use new style dialog as seen at the screenshot below:
Imgur
after you have selected use new style dialog and restarted notepad++, it will behave the following way:
if you try to “save as” or “rename” a file, that already has a | in it’s file name, it will not permit it and not even present you with a save as or rename dialogue. if you try to “save as” or “rename” any file that does not have a | in it’s filename yet, by adding a | to it’s current file name, it will correctly tell you “the file name is not valid” in an alert window.note: the use new style dialog is the prefered open/save dialogue setting if you are using a mac/linux/windows mixed environment, like i do.