"An unhandled exception was thrown by the Error Prone static analysis plugin"

[sikchi]

Following up on the exception message below:

An unhandled exception was thrown by the Error Prone static analysis plugin.
     Please report this at https://github.com/google/error-prone/issues/new and include the following:
     error-prone version: 2.36.0
     BugPattern: ComputeIfAbsentAmbiguousReference
     Stack Trace:
     java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
  	at jdk.compiler/com.sun.tools.javac.util.List.get(List.java:476)
  	at com.google.errorprone.bugpatterns.ComputeIfAbsentAmbiguousReference.matchMethodInvocation(ComputeIfAbsentAmbiguousReference.java:60)
  	at com.google.errorprone.scanner.ErrorProneScanner.processMatchers(ErrorProneScanner.java:509)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitMethodInvocation(ErrorProneScanner.java:824)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitMethodInvocation(ErrorProneScanner.java:170)
  	at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1832)
  	at jdk.compiler/com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:92)
  	at com.google.errorprone.scanner.Scanner.scan(Scanner.java:74)
  	at com.google.errorprone.scanner.Scanner.scan(Scanner.java:48)
  	at jdk.compiler/com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:96)
  	at jdk.compiler/com.sun.source.util.TreeScanner.visitVariable(TreeScanner.java:243)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitVariable(ErrorProneScanner.java:1017)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitVariable(ErrorProneScanner.java:170)
  	at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCVariableDecl.accept(JCTree.java:1040)
  	at jdk.compiler/com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:92)
  	at com.google.errorprone.scanner.Scanner.scan(Scanner.java:74)
  	at com.google.errorprone.scanner.Scanner.scan(Scanner.java:48)
  	at jdk.compiler/com.sun.source.util.TreeScanner.scan(TreeScanner.java:111)
  	at jdk.compiler/com.sun.source.util.TreeScanner.visitBlock(TreeScanner.java:272)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitBlock(ErrorProneScanner.java:591)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitBlock(ErrorProneScanner.java:170)
  	at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1104)
  	at jdk.compiler/com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:92)
  	at com.google.errorprone.scanner.Scanner.scan(Scanner.java:74)
  	at com.google.errorprone.scanner.Scanner.scan(Scanner.java:48)
  	at jdk.compiler/com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:96)
  	at jdk.compiler/com.sun.source.util.TreeScanner.visitMethod(TreeScanner.java:224)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitMethod(ErrorProneScanner.java:818)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitMethod(ErrorProneScanner.java:170)
  	at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:948)
  	at jdk.compiler/com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:92)
  	at com.google.errorprone.scanner.Scanner.scan(Scanner.java:74)
  	at com.google.errorprone.scanner.Scanner.scan(Scanner.java:48)
  	at jdk.compiler/com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:96)
  	at jdk.compiler/com.sun.source.util.TreeScanner.scan(TreeScanner.java:111)
  	at jdk.compiler/com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:119)
  	at jdk.compiler/com.sun.source.util.TreeScanner.visitClass(TreeScanner.java:203)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitClass(ErrorProneScanner.java:619)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitClass(ErrorProneScanner.java:170)
  	at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:855)
  	at jdk.compiler/com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:92)
  	at com.google.errorprone.scanner.Scanner.scan(Scanner.java:74)
  	at com.google.errorprone.scanner.Scanner.scan(Scanner.java:48)
  	at jdk.compiler/com.sun.source.util.TreeScanner.scan(TreeScanner.java:111)
  	at jdk.compiler/com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:119)
  	at jdk.compiler/com.sun.source.util.TreeScanner.visitCompilationUnit(TreeScanner.java:152)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitCompilationUnit(ErrorProneScanner.java:631)
  	at com.google.errorprone.scanner.ErrorProneScanner.visitCompilationUnit(ErrorProneScanner.java:170)
  	at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCCompilationUnit.accept(JCTree.java:623)
  	at jdk.compiler/com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:66)
  	at com.google.errorprone.scanner.Scanner.scan(Scanner.java:58)
  	at com.google.errorprone.scanner.ErrorProneScannerTransformer.apply(ErrorProneScannerTransformer.java:43)
  	at com.google.errorprone.ErrorProneAnalyzer.finished(ErrorProneAnalyzer.java:227)
  	at jdk.compiler/com.sun.tools.javac.api.MultiTaskListener.finished(MultiTaskListener.java:133)
  	at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.flow(JavaCompiler.java:1436)
  	at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.flow(JavaCompiler.java:1383)
  	at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:963)
  	at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.lambda$doCall$0(JavacTaskImpl.java:104)
  	at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.invocationHelper(JavacTaskImpl.java:152)
  	at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.doCall(JavacTaskImpl.java:100)
  	at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:94)
  	at org.codehaus.plexus.compiler.javac.JavaxToolsCompiler.compileInProcess(JavaxToolsCompiler.java:136)
  	at org.codehaus.plexus.compiler.javac.JavacCompiler.performCompile(JavacCompiler.java:183)
  	at org.apache.maven.plugin.compiler.AbstractCompilerMojo.execute(AbstractCompilerMojo.java:1140)
  	at org.apache.maven.plugin.compiler.CompilerMojo.execute(CompilerMojo.java:193)
  	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:126)
  	at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute2(MojoExecutor.java:328)
  	at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute(MojoExecutor.java:316)
  	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:212)
  	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:174)
  	at org.apache.maven.lifecycle.internal.MojoExecutor.access$000(MojoExecutor.java:75)
  	at org.apache.maven.lifecycle.internal.MojoExecutor$1.run(MojoExecutor.java:162)
  	at org.apache.maven.plugin.DefaultMojosExecutionStrategy.execute(DefaultMojosExecutionStrategy.java:39)
  	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:159)
  	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:105)
  	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:73)
  	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:53)
  	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:118)
  	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:261)
  	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:173)
  	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:101)
  	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:906)
  	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:283)
  	at org.apache.maven.cli.MavenCli.main(MavenCli.java:206)
  	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
  	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
  	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:255)
  	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:201)
  	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:361)
  	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:314)
  	at org.codehaus.classworlds.Launcher.main(Launcher.java:41)

[cushon]

Thanks for the report, can you share a repro, or any context about the specific code that the check crashed on?

Looking at the implementation, perhaps it was a custom Map implementation that defined an overload of computeIfAbsent with only one argument?

[sikchi]

Yes. here's the code snippet. calling lru.computeIfAbsent() results in above exception.

private static final class LRU extends LinkedHashMap<Key, V>
{
private static final float LOAD_FACTOR = 0.75f;
private final int cacheSize;
private final Function<List, List> getValues;

  private LRU (int cacheSize, Function<List<Key>, List<V>> getValues)
  {
     super((int) (cacheSize / LOAD_FACTOR), LOAD_FACTOR, true);
     this.cacheSize = cacheSize;
     this.getValues = getValues;
  }

  private List<V> computeIfAbsent (List<Key> keyList)
  {
     int n = keyList.size();
     ArrayList<V> values = new ArrayList<>(n);
     IntArrayList notFoundIndexes = new IntArrayList();
     List<Key> notFound = new ArrayList<>();
     for (int i = 0; i < n; i++)
     {
        Key key = keyList.get(i);
        V value = get(key);
        values.add(value);
        if (value == null)
        {
           notFoundIndexes.add(i);
           notFound.add(key);
        }
     }
     List<V> valuesToAdd = getValues.apply(notFound);
     for (int ii = 0; ii < notFoundIndexes.size(); ii++)
     {
        int i = notFoundIndexes.getInt(ii);
        Key key = keyList.get(i);
        V value = valuesToAdd.get(ii);
        putUnique(key, value);
        values.set(i, value);
     }
     List<V> result = Collections.unmodifiableList(values);
     return result;
  }

  private void putUnique (Key key, V value)
  {
     V previousValue = putIfAbsent(key, value);
     if (previousValue != null)
     {
        throw new UnsupportedOperationException("dup insertion attempted: key=" + key
              + ", previousValue=" + previousValue + ", value=" + value);
     }
  }

  @Override protected final boolean removeEldestEntry (Map.Entry<Key, V> eldest)
  {
     boolean result = (this.size() > cacheSize);
     return result;
  }

}