java.lang.ExceptionInInitializerError in AutoValueSubclassLeaked caused by NullPointerException in Caffeine

[sjamesr]

I'm getting the following crash inside error-prone on Java 8. Works fine on Java 11. It's not urgent for me, I'm happy to not support building on Java 8 at this point.

     error-prone version: 2.4.0
     BugPattern: AutoValueSubclassLeaked
     Stack Trace:
     java.lang.ExceptionInInitializerError
        at com.google.errorprone.bugpatterns.AutoValueSubclassLeaked$1.handle(AutoValueSubclassLeaked.java:83)
        at com.google.errorprone.bugpatterns.AutoValueSubclassLeaked$1.visitMemberSelect(AutoValueSubclassLeaked.java:72)
        at com.google.errorprone.bugpatterns.AutoValueSubclassLeaked$1.visitMemberSelect(AutoValueSubclassLeaked.java:69)
        at com.sun.tools.javac.tree.JCTree$JCFieldAccess.accept(JCTree.java:2112)
    <snip>
      Caused by: java.lang.NullPointerException
        at com.github.benmanes.caffeine.cache.LocalCacheFactory.newBoundedLocalCache(LocalCacheFactory.java:95)
        at com.github.benmanes.caffeine.cache.BoundedLocalCache$BoundedLocalManualCache.<init>(BoundedLocalCache.java:3392)
        at com.github.benmanes.caffeine.cache.BoundedLocalCache$BoundedLocalManualCache.<init>(BoundedLocalCache.java:3388)
        at com.github.benmanes.caffeine.cache.Caffeine.build(Caffeine.java:988)
        at com.google.errorprone.util.ASTHelpers.<clinit>(ASTHelpers.java:722)
        ... 66 more

To reproduce

Make sure OpenJDK 8 is available in JAVA_HOME, this example assumes it's in /usr/lib/java-8-openjdk-amd64/.

$ git clone [email protected]:sjamesr/jfreesane.git
$ cd jfreesane
$ git fetch origin pull/102/head
$ git checkout FETCH_HEAD
$ JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64/ ./gradlew check

What version of Error Prone are you using?

2.4.0, invoked by net.ltgt.errorprone plugin version 1.3.0.

Have you found anything relevant by searching the web?

No luck.

[cushon]

With

diff --git a/caffeine/src/javaPoet/java/com/github/benmanes/caffeine/cache/LocalCacheSelectorCode.java b/caffeine/src/javaPoet/java/com/github/benmanes/caffeine/cache/LocalCacheSelectorCode.java
index a368046d..345ef392 100644
--- a/caffeine/src/javaPoet/java/com/github/benmanes/caffeine/cache/LocalCacheSelectorCode.java
+++ b/caffeine/src/javaPoet/java/com/github/benmanes/caffeine/cache/LocalCacheSelectorCode.java
@@ -99,7 +99,7 @@ public final class LocalCacheSelectorCode {
   private LocalCacheSelectorCode selector() {
     block
         .beginControlFlow("try")
-            .addStatement("$T<?> clazz = $T.class.getClassLoader().loadClass(sb.toString())",
+            .addStatement("$T<?> clazz = java.util.Objects.requireNonNull($T.class.getClassLoader(), \"oh no\").loadClass(sb.toString())",
                 Class.class, LOCAL_CACHE_FACTORY)
             .addStatement("$T<?> ctor = clazz.getDeclaredConstructor($T.class, $T.class, $T.class)",
                 Constructor.class, BUILDER, CACHE_LOADER.rawType, TypeName.BOOLEAN)

I see

$ ./gradlew check --debug
...
[INFO] [org.gradle.workers.internal.WorkerDaemonStarter] Started Gradle worker daemon (0.326 secs) with fork options DaemonForkOptions{..., jvmArgs=[-Xbootclasspath/p:...caffeine-2.8.8-SNAPSHOT.jar...
...
[INFO] [org.gradle.api.internal.tasks.compile.JdkJavaCompiler] Compiling with JDK Java compiler API.
[ERROR] [system.err] ./jfreesane/src/main/java/au/com/southsky/jfreesane/package-info.java:10: error: An unhandled exception was thrown by the Error Prone static analysis plugin.
[ERROR] [system.err] package au.com.southsky.jfreesane;
[ERROR] [system.err] ^
[ERROR] [system.err]      Please report this at https://github.com/google/error-prone/issues/new and include the following:
[ERROR] [system.err]
[ERROR] [system.err]      error-prone version: 2.4.1-SNAPSHOT
[ERROR] [system.err]      BugPattern: AutoValueSubclassLeaked
[ERROR] [system.err]      Stack Trace:
[ERROR] [system.err]      java.lang.ExceptionInInitializerError
[ERROR] [system.err]       at com.google.errorprone.bugpatterns.AutoValueSubclassLeaked$1.handle(AutoValueSubclassLeaked.java:83)
[ERROR] [system.err]       at com.google.errorprone.bugpatterns.AutoValueSubclassLeaked$1.visitMemberSelect(AutoValueSubclassLeaked.java:72)
...
[ERROR] [system.err]   Caused by: java.lang.NullPointerException: oh no
[ERROR] [system.err]       at java.util.Objects.requireNonNull(Objects.java:228)
[ERROR] [system.err]       at com.github.benmanes.caffeine.cache.LocalCacheFactory.newBoundedLocalCache(LocalCacheFactory.java:88)

I reported this against caffeine as ben-manes/caffeine#481

I'm not sure why gradle is using -Xbootclasspath/p: there, having caffeine on the regular classpath should avoid the crash. With JDK 8, Error Prone expects error-prone-javac to be on the bootclasspath, but everything else can be on the regular classpath. Maybe the gradle plugin is just putting everything on the bootclasspath?

[sjamesr]

Thanks for taking a look. I dug into the Error Prone gradle plugin a little bit (which you can debug directly from intellij, kinda nice), see https://github.com/tbroyer/gradle-errorprone-plugin/blob/master/src/main/kotlin/net/ltgt/gradle/errorprone/ErrorPronePlugin.kt#L87

        fun JavaCompile.configureErrorProneJavac() {
            if (!options.isFork) {
                options.isFork = true
                // reset forkOptions in case they were configured
                options.forkOptions = ForkOptions()
            }
            javacConfiguration.asPath.also {
                if (it.isNotBlank()) {
                    options.forkOptions.jvmArgs!!.add("-Xbootclasspath/p:$it")    // error prone and caffeine added to bootclasspath
                } else if (noJavacDependencyNotified.compareAndSet(false, true)) {
                    LOGGER.warn(NO_JAVAC_DEPENDENCY_WARNING_MESSAGE)
                }
            }
        }

There is code further down in the plugin that does this only for Java 8:

                        JavaVersion.current().isJava8 && (!options.isFork || (options.forkOptions.javaHome == null && options.forkOptions.executable == null)) ->
                            configureErrorProneJavac()

Is this a problem with the plugin, or should Caffeine be able to operate in this mode?

[cushon]

Thanks for investigating!

@tbroyer FYI

Is this a problem with the plugin, or should Caffeine be able to operate in this mode?

Maybe kinda both? :) Ideally Caffeine would work in this mode, but if it's possible for the plugin to only put the error-prone-javac artifact on the boothclasspath, and not all of Error Prone, that's probably worthwhile too.

[ben-manes]

Thank you for the bug report. Please upgrade caffeine to 2.8.8 to resolve this issue.

[tbroyer]

The Gradle plugin will only put on the bootclasspath the dependencies declared in the errorproneJavac configuration, which should only be com.google.errorprone:javac if you configured your project correctly. ErrorProne (error_prone_core) and its dependencies (including Caffeine) should only be configured in the errorprone configuration, which is only added to the annotation processor path; and this is indeed not what was done here:
https://github.com/sjamesr/jfreesane/blob/da772013bdc45f11c0e7111a1a77684d9075ddf3/build.gradle#L35-L36

This should be

    errorprone 'com.google.errorprone:error_prone_core:2.3.3'
    errorproneJavac 'com.google.errorprone:javac:9+181-r4173-1'

[sjamesr]

Aha, thank you!