RFR: 8332297: annotation processor that generates records sometimes fails due to NPE in javac

[Vicente Romero]

This bug is a bit particular regarding how to reproduce it. Having:

import java.lang.annotation.*;
public @interface RecordBuilder {}

interface Conf {
    int maxConcurrency( );
}

and:

import java.lang.annotation.*;
public @interface RecordBuilder {
}

and:

import java.util.*;
import java.io.*;

import javax.annotation.processing.*;
import javax.lang.model.element.TypeElement;
import javax.tools.StandardLocation;

@SupportedAnnotationTypes("*")
public class SimplestAP extends AbstractProcessor {
    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        if (roundEnv.processingOver()) {
            try (Writer w = processingEnv.getFiler().createSourceFile("ConfRecord").openWriter()) {
                w.append("@RecordBuilder public record ConfRecord(int maxConcurrency) implements Conf {}");
            } catch (IOException ex) {
                throw new IllegalStateException(ex);
            }
        }
        return true;
    }
}

do:

javac SimplestAP.java

javac -processor SimplestAP Conf.java //compiles fine
javac -processor SimplestAP Conf.java // fails with:


warning: No SupportedSourceVersion annotation found on SimplestAP, returning RELEASE_6.
warning: Supported source version 'RELEASE_6' from annotation processor 'SimplestAP' less than -source '23'
warning: File for type 'ConfRecord' created in the last round will not be subject to annotation processing.
3 warnings
An exception has occurred in the compiler (23-internal). Please file a bug against the Java compiler via the Java bug reporting page (https://bugreport.java.com/) after checking the Bug Database (https://bugs.java.com/) for duplicates. Include your program, the following diagnostic, and the parameters passed to the Java compiler in your report. Thank you.
java.lang.NullPointerException: Cannot invoke "com.sun.tools.javac.code.Symbol$MethodSymbol.flags()" because "rc.accessor" is null
at jdk.compiler/com.sun.tools.javac.comp.Lower.lambda$generateMandatedAccessors$6(Lower.java:2403)
at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:196)
at java.base/java.util.Iterator.forEachRemaining(Iterator.java:133)
at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1939)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:570)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:560)
at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:265)
at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:727)
at jdk.compiler/com.sun.tools.javac.comp.Lower.generateMandatedAccessors(Lower.java:2410)
at jdk.compiler/com.sun.tools.javac.comp.Lower.visitRecordDef(Lower.java:2607)
at jdk.compiler/com.sun.tools.javac.comp.Lower.visitClassDef(Lower.java:2300)
at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:855)
at jdk.compiler/com.sun.tools.javac.tree.TreeTranslator.translate(TreeTranslator.java:58)
at jdk.compiler/com.sun.tools.javac.comp.Lower.translate(Lower.java:2192)
at jdk.compiler/com.sun.tools.javac.comp.Lower.translate(Lower.java:2211)
at jdk.compiler/com.sun.tools.javac.comp.Lower.translateTopLevelClass(Lower.java:4475)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.desugar(JavaCompiler.java:1647)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.desugar(JavaCompiler.java:1467)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:977)
at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:319)
at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:178)
at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:66)
at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:52)

so the first time file ConfRecord.java is produced by the annotation processor, and later compiled by javac so all the information is gathered from a source file. The second time, ConfRecord.class is found, loaded and symbol for ConfRecord is completed from there. As the class file doesn't store the position of the record components in the original source file, method `ClassSymbol::findRecordComponentToRemove` won't find a match when trying to remove a record component and then two record components with the same name gets added to the record, currently we try to match on name and position. But for one of them there won't be an accessor assigned. We remove record components when dealing with annotation processors to make sure that later on we are propagating the correct annotations to other record elements the annotations could be applicable to.

The proposal here is to match only on name if the position is `-1` which is the default for all record components when the record class has been loaded from a class file.

TIA

-------------

Commit messages:
 - 8332297: annotation processor that generates records sometimes fails due to NPE in javac

Changes: https://git.openjdk.org/jdk/pull/19288/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19288&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332297
  Stats: 152 lines in 2 files changed: 150 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19288.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19288/head:pull/19288

PR: https://git.openjdk.org/jdk/pull/19288