ClassCastException in Java code completion

[nmatt]

Apache NetBeans version

Apache NetBeans 28

What happened

The following ClassCastException repeatedly occurred during code completion in a file with syntax errors, intermittently breaking code completion:

java.lang.ClassCastException: class com.sun.tools.javac.code.Symbol$ClassSymbol cannot be cast to class javax.lang.model.element.ExecutableElement (com.sun.tools.javac.code.Symbol$ClassSymbol and javax.lang.model.element.ExecutableElement are in unnamed module of loader org.netbeans.StandardModule$OneModuleClassLoader @1426fa1e)
	at org.netbeans.modules.java.completion.JavaCompletionTask.getSmartTypesImpl(JavaCompletionTask.java:5999)
	at org.netbeans.modules.java.completion.JavaCompletionTask.getSmartTypes(JavaCompletionTask.java:5728)
	at org.netbeans.modules.java.completion.JavaCompletionTask.addMembers(JavaCompletionTask.java:4083)
	at org.netbeans.modules.java.completion.JavaCompletionTask.insideMemberSelect(JavaCompletionTask.java:1909)
	at org.netbeans.modules.java.completion.JavaCompletionTask.resolve(JavaCompletionTask.java:380)
	at org.netbeans.modules.java.completion.BaseTask.run(BaseTask.java:96)
	at org.netbeans.modules.java.completion.JavaCompletionTask.run(JavaCompletionTask.java:67)
	at org.netbeans.modules.parsing.impl.TaskProcessor.callUserTask(TaskProcessor.java:586)
	at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:197)
	at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:180)
	at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:181)
	at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:178)
	at org.netbeans.modules.masterfs.filebasedfs.utils.FileChangedManager.priorityIO(FileChangedManager.java:153)
	at org.netbeans.modules.masterfs.providers.ProvidedExtensions.priorityIO(ProvidedExtensions.java:335)
	at org.netbeans.modules.parsing.nb.DataObjectEnvFactory.runPriorityIO(DataObjectEnvFactory.java:118)
	at org.netbeans.modules.parsing.impl.Utilities.runPriorityIO(Utilities.java:67)
	at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:178)
Caused: org.netbeans.modules.parsing.spi.ParseException
	at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:186)
	at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:83)
[catch] at org.netbeans.modules.editor.java.JavaCompletionProvider$JavaCompletionQuery.query(JavaCompletionProvider.java:193)
	at org.netbeans.spi.editor.completion.support.AsyncCompletionTask.run(AsyncCompletionTask.java:198)
	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1403)
	at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:45)
	at org.openide.util.lookup.Lookups.executeWith(Lookups.java:287)
	at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2018)

Language / Project Type / NetBeans Component

No response

How to reproduce

I can't provide the code where this happened (large file in a large proprietary code base), but the situation was that additional parameters were added to an existing method (temporarily breaking call sites for that method in the same source file), and the ClassCastException occurred while performing code completion within the argument list of one of the callers (while trying to add the new arguments for the new method parameters).

Similar to:

void foo()
{
    bar(arg1, arg2, newArg2.<code completion here> );
}

void bar( A arg1, B arg2, C newArg3, D newArg4, E newArg5)
{
    ... also some syntax errors here ...
}

Closing the source file and reopening it, and first filling null for the multiple missing method arguments before re-attempting code completion, made code completion working again.

Did this work correctly in an earlier version?

No / Don't know

Operating System

Windows

JDK

JDK 21

Apache NetBeans packaging

Apache NetBeans binary zip

Anything else

While I can't provide a reproducible example, maybe the mismatched types causing the ClassCastException and the stacktrace are sufficient to track down where the bug is.

Are you willing to submit a pull request?

No

[mbien]

it probably shouldn't be possible that the TypeMirror of a path is of TypeKind.EXECUTABLE while the Element of the same path is something else outside of ExecutableElement. The code at least assumes right now that this is always the case.

We could probably add an instanceof there which would fix the CCE but my guess is that completion won't work very well still if this situation occurs.

[nmatt]

@mbien: I regularly run into situations where NetBeans' internal index seems to be broken to various degrees. Sometimes just exceptions like here, sometimes imports that don't resolve anymore in the editor although the classes exist and external compilation has no issues. Oftentimes I have to wipe the index cache on disk to get NetBeans to parse and resolve everything correctly again. Unfortunately I have large projects where reindexing takes considerable time. My question: Is there a workable approach for tracking down what is causing problems of this sort? Maybe some existing instrumentation of the indexing logic and usage?

[mbien]

not sure, I haven't looked into debugging indexing yet. But I also don't think an issue like this would have to be index related.