Hi Marc!
We indeed moved this configuration option from servers to projects. Having (or not having) a need for this is related to configuration and structure of a particular project, not a particular server. It was perfectly possible that one server mixed projects that did need this option turned off and projects for which having it on was preferred. That’s why it made sense to move it.
The default for this option checkbox is ON => meaning that if you have a project where all the classes and resources are properly mapped, JRebel will delete classes/resources on the server side that it does not find on the IDE side. This means you can also _remove_ stuff with JRebel, not just cumulatively add it (giving a fuller experience). This will work well for a maven project where all your compiled classes are under target/classes, all your resources are under src/main/resources, both of these locations are mapped by your rebel.xml, and this is basically all your .war file consists of.
But problems arise when your project’s mappings in the rebel.xml file are incomplete, for some reason. This is why we need to provide a way to turn this deletion off. This will more easily happen with build tools like Ant, where the project structure is not that clearly defined. If this option is OFF, then JRebel will NOT delete any resource on the remote server that it cannot find on IDE workspace based on the rebel.xml.
In this situation, the first thing you could try to do is have a look why the rebel.xml mapping for the project is not complete => is some classes or resources directory that gets included into the .war, not included into the rebel.xml mappings file? If so, try adding it.
If you don’t want to mess with the rebel.xml fine-tuning, then yeah, turn it off for that particular project. But in general – you shouldn’t be doing it for all projects. Just for the ones that have problems otherwise.
What build tool are you using and how did you generate your rebel.xml files? If you want to send an example file in confidentially and discuss, send it to support at zeroturnaround.com. I’d be glad to learn more about your scenario and why the current approach doesn’t satisfy you.
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Sander Sõnajalg
JRebel product manager