Stub files can no longer undo the class @NonNull annotation on, e.g., Optional

[cpovirk]

Inside Google, we (maybe intentionally, maybe not) have a stub for java.util.Optional that undoes the class @NonNull annotation on that type, using the approach from its CFComment. As part of the upgrade from 3.21.4-eisop1 to 3.24.0-eisop1, that stops working. I notice that typetools 3.24.0 still works, so I'm wondering if this is fallout from the eisop extends @Nullable Object fixes, similar to #204, or from the eisop stub-file fix of #247. I haven't done any binary searching across releases, though, let alone commits. [edit: After writing that, I started with git bisect. But I ran into trouble because the build process doesn't automatically know which commit of stubparser to check out when building older versions.]

$ tail -n +1 X.java mystubs.astub 
==> X.java <==
import org.checkerframework.checker.nullness.qual.Nullable;

interface X {
  java.util.@Nullable Optional<String> o();
}

==> mystubs.astub <==
package java.util;
class Optional<T> {}

checker-framework-3.21.4-eisop1 $ checker/bin/javac -Astubs=mystubs.astub -processor nullness X.java
warning: /usr/local/google/home/cpovirk/checker-framework-3.21.4-eisop1/mystubs.astub: No supported annotations found! Does stub file /usr/local/google/home/cpovirk/checker-framework-3.21.4-eisop1/mystubs.astub import them?
1 warning

checker-framework-3.24.0-eisop1 $ checker/bin/javac -Astubs=mystubs.astub -processor nullness X.java
warning: /usr/local/google/home/cpovirk/checker-framework-3.24.0-eisop1/mystubs.astub: No supported annotations found! Does stub file /usr/local/google/home/cpovirk/checker-framework-3.24.0-eisop1/mystubs.astub import them?
X.java:4: error: [type.invalid.annotations.on.use] invalid type: annotations [@Initialized, @Nullable] conflict with declaration of type java.util.Optional
  java.util.@Nullable Optional<String> o();
                                       ^
1 error
1 warning

checker-framework-3.24.0 $ checker/bin/javac -Astubs=mystubs.astub -processor nullness X.java
warning: /usr/local/google/home/cpovirk/checker-framework-3.24.0/mystubs.astub: No supported annotations found! Does stub file /usr/local/google/home/cpovirk/checker-framework-3.24.0/mystubs.astub import them?
1 warning

@amalloy

[wmdietl]

@cpovirk Thanks for the detailed report and sorry for the trouble.
I've created a test in #324 and narrowed the issue down to being introduced in #305.

[cpovirk]

No worries, and thanks!

(Also: Ooo, I wonder if #305 helps with any of the challenges we've seen when trying to read @NullMarked from stub files from our reference checker! (It's been a while, so I forget the details.) And even if not, fixing any missing annotations is a good thing :))

[wmdietl]

Yes, #305 should fix parsing annotations e.g. in package-info.java files.
Let us get this issue fixed and then you can let us know if you're still running into issues.

[cpovirk]

This does fix our issue. Thanks!