This is similar in some ways to #1660, but filing for separate discussion since that's about the Dart side, and this is about the Java side.

In my experience doing hybrid (part Dart, part native code) plugin development, it's common to need to iterate on the API boundary during the development process. Sometimes that iteration is driven by changes on the Dart side, sometimes on the native code side. Often when I find something I need to adjust, I am mid-change.

• In Pigeon, I just go change my API definition file, re-run the generated (almost instant), and continue working
• With Obj-C ffigen, I go change the relevant header(s) and re-run ffigen (very fast if I don't autoformat) and continue working
• With jnigen, I have to build the entire app. Not only is that orders of magnitude slower than the other two, it requires that all of my Java code be in a good state (and currently my Dart code due to jnigen iterative development loop with plugin code is awkward #1660, but let's imagine that's fixed for the purposes of this discussion).

Having to stop, clean up any code I have that's in an intermediate state, and then build the entire app, just to iterate my Dart code, is a much worse experience than the Pigeon equivalent. Is there some way we could have a fast-iteration mode that's based on source without it being a config-level option, maybe?