PMD not recognizing 'super' keyword in Java

[NathanMacDiarmid]

I am testing a rule against Java classes and it seems to work but I continue getting this error at some points:

I have pinpointed where it is in the code, which is here:

Its error when hovered over is: Type mismatch: cannot convert from Iterable to Iterable

I do not know PMD well enough to solve this issue, but I believe that any time it detects the 'super' keyword, it calls this function which in turn throws an error. I have tested it against many Java classes both with the 'super' keyword and without and it only throws this error on classes that contain the 'super' keyword. Any suggestions on how I can fix this locally and allow for the detection of the 'super' keyword while parsing?

[jsotuyod]

Interesting… you are not setting the auxclasspath which will affect result quality, but it shouldn't fail with an exception…

Can you share a snippet of code that triggers this?

[NathanMacDiarmid]

Where would I set the auxclasspath?

[jsotuyod]

Since you are using the CLI, you should look at this https://docs.pmd-code.org/latest/pmd_userdocs_cli_reference.html#:~:text=%2D%2Daux%2Dclasspath%C2%A0%3Ccp%3E

[NathanMacDiarmid]

@jsotuyod Thank you for your help! I was able to solve it with another suggestion.

[adangel]

The "Unresolved Compilation Error" is problematic. This means, that building PMD continued despite the fact, that there were build problems. I know this from Eclipse, that it can partially compile classes even though they have syntax errors...

How did you build PMD? Which JDK do you use? Does this problem also happen with the official builds from https://sourceforge.net/projects/pmd/files/pmd/7.0.0-SNAPSHOT/? (If yes, it is a general problem)

For reference, we you Adoptium Temurin 11 when compiling PMD (https://adoptium.net/de/temurin/releases/?version=11). And we compile it under Linux.

Whatever compiler you use, it is not able to infer the correct type of "ctor" in the lambda... I know, that the eclipse compiler has problems and I'm not sure e.g. if PMD can still be developed using Eclipse. I see, that you use VS Code. Maybe there is some option to configure, which JDK to use?

[NathanMacDiarmid]

We have used both JDK 20 and JDK 17, both result in this error. We can change the JDK version manually before we build. We build PMD using this command: ./mvnw clean package -Dmaven.skip.tests=true -Dmaven.skip.javadoc=true -Pcli-dist

Not sure if that problem exists on the official PMD, but we are building a VS Code extension for our fourth year project using PMD as the code parser specifically for Java. We removed a lot of code so that compile times are faster for testing and implementation purposes. Our forked branch can be found here: https://github.com/JavaTech-Nomads/java_pmd_with_our_rules
Could we have removed something that was needed to infer the type of ctor?

[oowekyala]

It's unlikely if you haven't removed pieces of pmd-java. Anyway the issue is not with the type inference of constructors by pmd. As Andreas said, it's your Java compiler that fails to compile part of the PMD source code and inserts a throw new Error at that point instead of giving up. The only compiler I know that does that is the Eclipse compiler. Maybe the vscode plugin for java is using it under the hood through the Java language server. Maybe you're building from within vscode? (I reproduced your problem this way.) Does the problem happen if you're running the maven build command from a terminal, with vscode closed?

[adangel]

Yes - The extension Language Support for Java(TM) by Red Hat uses the Eclipse Language Server and Eclise JDT under the hood.
The problem seems to happen, if VS Code compiles the project at the same time the maven build is compiling - then it can be that in the produced jar file, the bad compilation result from Eclipse JDT is added. As @oowekyala suggested, exit vscode, and run maven without vscode, then it should work (This seems to be the only reliable way).

By the way, with your command line, you are not skipping tests and javadoc. The property need to be "maven.test.skip" and "maven.javadoc.skip":

./mvnw clean package -Dmaven.test.skip=true -Dmaven.javadoc.skip=true -Pcli-dist

Instead of forking the main repository and deleting what you don't need, you might want to look at this example here: https://github.com/pmd/pmd-examples/blob/main/custom-rules/maven-java/README.md
This shows how to develop custom rules in a separate repository, pull in PMD as a dependency and also built a custom distribution with only the wanted modules.

[NathanMacDiarmid]

@adangel the link and example you sent works and fixes our issue perfectly! Thank you very much for this!