Currently it looks like 'mach build' always does a Java build and processes the annotations, even if nothing changed.

(In reply to James Willcox (:snorp) (jwillcox@mozilla.com) from comment #0) > Currently it looks like 'mach build' always does a Java build and processes > the annotations, even if nothing changed. This is true, more or less, although it's a no-op when nothing has changed. Logs would convince me that we're doing too much. I do believe we invoke the annotation processor, even when we don't need to, and trust that the processor doesn't write files when they're unchanged -- we could save that. Saving all the run-up -- the Java jobs, etc -- would be possible (maybe?) but fragile. One thing that you might be seeing is that |mach build| processes the annotations for the _official..._ target, and in the IDE you'll be modifying the _local..._ targets. Those annotations can, in theory be different. This means you'll see "extra" Java compilation just 'cuz we're duplicating work. Avoiding that is Rather Complicated, and I don't have a good plan for that yet.