An “overwrite” option for this could help:
And another combined option would help keeping the compiled project folder clean
cleanBeforeCopy, to delete and rewrite everything.
I think that performances change very few, I hardly distinguish the difference between an all new recompile (Flash and HTML5) and an “overwrite newer” one, maybe it is noticeable only for very big projects.
I know a project that copies more than a GB of data. That’s noticeable 
You could use -clean when building, but I understand it would be nice to not have to do this when switching. I’ll have to think about it – sources are an array of strings path at the moment, so adding a special property per path would require tool changes, though “always clean” would not, I suppose (since it would be global)
Like this
html5 -clean
?
yeah, openfl test html5 -clean will delete the output directory and re-copy all assets each time 
In the target dropdown box?
Actually, in FlashDevelop, adding “-clean” in the target drop-down will break things, but I think in the project settings there is a “clean build” option. Use -clean if you are running from the command-line
Ok, command line option works! Thanks!