You can put an ON / OFF option which will decide wheather to trim white spaces or not from each line in currently opened file at the time of saving the file.
Or you can ask user to specify characters to be trimmed at the end of the line in your Default File Preferences
//set to true if you want to trim lines for white spaces at the time of saving file."trim_on_save": true,//specify charaters to trim. It will trim if trim_on_save option is true."trim_characters": " \t",
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