How can I have the API sources from a mod and the actual mod together into a development environment?

 

The API source files are added to the project to be able to compile against the API, but if I add the mod itself for testing purposes to the run/mods folder I always get java.lang.NoSuchMethodError when something tries to use the API. Is there a way to have both at once in the dev environment - the API sources for compiling against and the mod itself for testing the stuff in the debugger?

You should be able to add the API as a

compile

dependency and the mod itself as a

runtime

dependency like JEI recommends.

And if the API is just copied over as files as there is no package for it?

Adding the API source to src/api/java should work. Otherwise you'll probably just need to compile against the mod itself and limit yourself to the API classes.

 

You can add a dependency as

deobfCompile

or

deobfProvided

to have ForgeGradle deobfuscate it on disk.