Allow to silently ignore signatures if the class is not found

[uschindler]

(e.g., multi-module builds with common signatures). The old setting failOnUnresolvableSignatures was deprecated in favour of ignoreSignaturesOfMissingClasses. This closes #83

[uschindler]

This is the main point doing the magic!

[asdf2014]

Hi @uschindler . We found that after replacing the failOnUnresolvableSignatures old parameter with this ignoreSignaturesOfMissingClasses new parameter, it did not work well with Maven's Shade plugin. After adding the old parameters back, everything works fine. You can got more details from here. PTAL, thanks a lot.

[uschindler]

Hi @asdf2014,
Thanks for reporting. I have not yet looked into your code and why this does not work with renamed classes. I have no idea about the setup (so it looks like you shade one version of a library and then refer to the shaded version from source code?).

ignoreSignaturesOfMissingClasses only ignores missing classes, but failOnUnresolvableSignatures ignores any wrongly written signature (but it is deprecated now).

ignoreSignaturesOfMissingClasses works well when you have a subproject where a dependency is missing and you still want to use the same signatures file. In that case it just ignores all signatures where the class was not found. This should work also for shaded jars.

Do you have a simple example or maybe can you tell me how to trigger that after checking out Druid?

[uschindler]

Ah now I understand the problem:

[2022-01-15 05:49:23] [build-stdout] [2022-01-15 05:49:23] [autobuild] [ERROR] Failed to execute goal de.thetaphi:forbiddenapis:3.1:check (compile) on project opentelemetry-emitter: Parsing signatures failed: Method not found while parsing signature: com.google.common.util.concurrent.MoreExecutors#sameThreadExecutor() -> [Help 1]

So the class is there, but the method is missing (because it is another version of Google Guava). This of course fails. The idea behind the ignoreSignaturesOfMissingClasses is to just ignore signatures where class is missing. But this is not the case here.

The old setting was deprecated because it makes parsing signatures files a bit errorprone: If you have a typo in signatures file it won't fail the build.