[1.15]Addon mod problem

When I wrote mod-A, I applied another mod-B (I wrote it myself, which has been obfuscated), so in the build.gradle I edited the following:

dependencies {
minecraft 'net.minecraftforge:forge:1.15.2-31.2.36'
compile fg.deobf(files('mod-B.jar'))//👈
}

The following problems are encountered in the build dependencies period:

files(...) dependencies are not deobfuscated. Use a flatDir repository instead.
Cannot deobfuscate dependency of type DefaultSelfResolvingDependency_Decorated, using obfuscated version!

The deobfuscation is skipped, directly compiled and run, resulting in various functions and field errors...

So the problem is:

How to correctly [import/compile] an existing mod when developing the addon mod?