warning: unknown enum constant ReflectionSupport$Level.FULL when building Gerrit on Bazel 0.19.0rc5

[davido]

When building Gerrit on 0.19.0rc5 we are seeing this warning:

  $ bazel version
Build label: 0.19.0rc5

  $ bazel build :headless
Starting local Bazel server and connecting to it...
INFO: Analysed target //:headless (223 packages loaded, 4218 targets configured).
INFO: Found 1 target...
INFO: From Building external/com_google_protobuf/libprotobuf_java.jar (77 source files, 1 source jar):
warning: [options] source value 1.6 is obsolete and will be removed in a future release
warning: [options] target value 1.6 is obsolete and will be removed in a future release
warning: [options] To suppress warnings about obsolete options, use -Xlint:-options.
INFO: From Building java/com/google/gerrit/lucene/liblucene.jar (12 source files):
warning: unknown enum constant ReflectionSupport$Level.FULL
  reason: class file for com.google.j2objc.annotations.ReflectionSupport$Level not found
Target //:headless up-to-date:
  bazel-bin/headless.war
INFO: Elapsed time: 90.364s, Critical Path: 70.20s, Remote (0.00% of the time): [queue: 0.00%, setup: 0.00%, process: 0.00%]
INFO: 117 processes: 2 remote cache hit, 55 linux-sandbox, 60 worker.
INFO: Build completed successfully, 118 total actions

Reported upstream in: [1].

• [1] https://bugs.chromium.org/p/gerrit/issues/detail?id=9779

[dpursehouse]

FTR I'm also seeing it on bazel 0.17.1

[benjaminp]

Probably a dup of #5985.

[cushon]

Yep, sounds like #5985.

Does --java_classpath=off affect the warnings that are produced? (I'm not recommending that as a work-around, but it would provide some information about the cause of the warnings.)

[davido]

Does --java_classpath=off affect the warnings that are produced?

No, it doesn't:

$ bazel build --java_classpath=off :headless
INFO: Build options have changed, discarding analysis cache.
INFO: Analysed target //:headless (0 packages loaded, 4216 targets configured).
INFO: Found 1 target...
INFO: From Building java/com/google/gerrit/lucene/liblucene.jar (12 source files):
warning: unknown enum constant ReflectionSupport$Level.FULL
  reason: class file for com.google.j2objc.annotations.ReflectionSupport$Level not found
[...]

I also don't see where ReflectionSupport$Level.FULL is coming from. Gerrit doesn't use it directly.

[cushon]

OK. It sounds like the warning is working as intended, then: the classpath contains a reference to com.google.j2objc.annotations.ReflectionSupport, which isn't on the classpath.

[davido]

It seems to be a transitive dependency on guava and is used like this:

java_library(
    name = "j2objc",
    data = ["//lib:LICENSE-Apache2.0"],
    visibility = ["//visibility:public"],
    exports = ["@j2objc//jar"],
)

java_library(
    name = "guava",
    data = ["//lib:LICENSE-Apache2.0"],
    visibility = ["//visibility:public"],
    exports = ["@guava//jar"],
    runtime_deps = [":j2objc"],
)

And this diff fixed that:

diff --git a/lib/BUILD b/lib/BUILD
index e5034c9c60..95ca4db461 100644
--- a/lib/BUILD
+++ b/lib/BUILD
@@ -90,8 +90,10 @@ java_library(
     name = "guava",
     data = ["//lib:LICENSE-Apache2.0"],
     visibility = ["//visibility:public"],
-    exports = ["@guava//jar"],
-    runtime_deps = [":j2objc"],
+    exports = [
+        ":j2objc",
+        "@guava//jar",
+    ],
 )