When testing the Lucene/Solr builds with JDK 17 EA we figured out that javac fails when doclint is enabled. It produces the following error:

common.compile-test:
    [mkdir] Created dir: C:\Users\Uwe Schindler\Projects\lucene\lusolr\solr\build\contrib\solr-dataimporthandler\classes\test
    [javac] Compiling 48 source files to C:\Users\Uwe Schindler\Projects\lucene\lusolr\solr\build\contrib\solr-dataimporthandler\classes\test
    [javac] Note: Some input files use or override a deprecated API.
    [javac] Note: Recompile with -Xlint:deprecation for details.
    [javac] An exception has occurred in the compiler (17-ea). Please file a bug against the Java compiler via the Java bug reporting page (http://bugreport.java.com) after checking the Bug Database (http://bugs.java.com) for duplicates. Include your program, the following diagnostic, and the parameters passed to the Java compiler in your report. Thank you.
    [javac] com.sun.tools.javac.util.ClientCodeException: java.lang.NullPointerException: Cannot read field "endKind" because "tag" is null
    [javac] at jdk.compiler/com.sun.tools.javac.api.ClientCodeWrapper$WrappedTaskListener.started(ClientCodeWrapper.java:857)
    [javac] at jdk.compiler/com.sun.tools.javac.api.MultiTaskListener.started(MultiTaskListener.java:119)
    [javac] at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.attribute(JavaCompiler.java:1336)
    [javac] at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:973)
    [javac] at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:317)
    [javac] at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:176)
    [javac] at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:64)
    [javac] at jdk.internal.reflect.GeneratedMethodAccessor217.invoke(Unknown Source)
    [javac] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    [javac] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    [javac] at org.apache.tools.ant.taskdefs.compilers.Javac13.execute(Javac13.java:56)
    [javac] at org.apache.tools.ant.taskdefs.Javac.compile(Javac.java:1153)
    [javac] at org.apache.tools.ant.taskdefs.Javac.execute(Javac.java:930)
    [javac] at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
    [javac] at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
    [javac] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    [javac] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    [javac] at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
    [javac] at org.apache.tools.ant.Task.perform(Task.java:348)
    [javac] at org.apache.tools.ant.taskdefs.Sequential.execute(Sequential.java:68)
    [javac] at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
    [javac] at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
    [javac] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    [javac] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    [javac] at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
    [javac] at org.apache.tools.ant.Task.perform(Task.java:348)
    [javac] at org.apache.tools.ant.taskdefs.MacroInstance.execute(MacroInstance.java:398)
    [javac] at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
    [javac] at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
    [javac] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    [javac] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    [javac] at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
    [javac] at org.apache.tools.ant.Task.perform(Task.java:348)
    [javac] at org.apache.tools.ant.taskdefs.Sequential.execute(Sequential.java:68)
    [javac] at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
    [javac] at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
    [javac] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    [javac] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    [javac] at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
    [javac] at org.apache.tools.ant.Task.perform(Task.java:348)
    [javac] at org.apache.tools.ant.taskdefs.MacroInstance.execute(MacroInstance.java:398)
    [javac] at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
    [javac] at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
    [javac] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    [javac] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    [javac] at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
    [javac] at org.apache.tools.ant.Task.perform(Task.java:348)
    [javac] at org.apache.tools.ant.Target.execute(Target.java:392)
    [javac] at org.apache.tools.ant.Target.performTasks(Target.java:413)
    [javac] at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1399)
    [javac] at org.apache.tools.ant.helper.SingleCheckExecutor.executeTargets(SingleCheckExecutor.java:38)
    [javac] at org.apache.tools.ant.Project.executeTargets(Project.java:1251)
    [javac] at org.apache.tools.ant.taskdefs.Ant.execute(Ant.java:442)
    [javac] at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
    [javac] at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
    [javac] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    [javac] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    [javac] at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
    [javac] at org.apache.tools.ant.Task.perform(Task.java:348)
    [javac] at org.apache.tools.ant.Target.execute(Target.java:392)
    [javac] at org.apache.tools.ant.Target.performTasks(Target.java:413)
    [javac] at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1399)
    [javac] at org.apache.tools.ant.helper.SingleCheckExecutor.executeTargets(SingleCheckExecutor.java:38)
    [javac] at org.apache.tools.ant.Project.executeTargets(Project.java:1251)
    [javac] at org.apache.tools.ant.taskdefs.Ant.execute(Ant.java:442)
    [javac] at org.apache.tools.ant.taskdefs.SubAnt.execute(SubAnt.java:303)
    [javac] at org.apache.tools.ant.taskdefs.SubAnt.execute(SubAnt.java:221)
    [javac] at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
    [javac] at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
    [javac] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    [javac] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    [javac] at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
    [javac] at org.apache.tools.ant.Task.perform(Task.java:348)
    [javac] at org.apache.tools.ant.taskdefs.Sequential.execute(Sequential.java:68)
    [javac] at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
    [javac] at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
    [javac] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    [javac] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    [javac] at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
    [javac] at org.apache.tools.ant.Task.perform(Task.java:348)
    [javac] at org.apache.tools.ant.taskdefs.MacroInstance.execute(MacroInstance.java:398)
    [javac] at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
    [javac] at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
    [javac] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    [javac] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    [javac] at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
    [javac] at org.apache.tools.ant.Task.perform(Task.java:348)
    [javac] at org.apache.tools.ant.Target.execute(Target.java:392)
    [javac] at org.apache.tools.ant.Target.performTasks(Target.java:413)
    [javac] at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1399)
    [javac] at org.apache.tools.ant.helper.SingleCheckExecutor.executeTargets(SingleCheckExecutor.java:38)
    [javac] at org.apache.tools.ant.Project.executeTargets(Project.java:1251)
    [javac] at org.apache.tools.ant.taskdefs.Ant.execute(Ant.java:442)
    [javac] at org.apache.tools.ant.taskdefs.SubAnt.execute(SubAnt.java:303)
    [javac] at org.apache.tools.ant.taskdefs.SubAnt.execute(SubAnt.java:221)
    [javac] at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
    [javac] at jdk.internal.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
    [javac] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    [javac] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    [javac] at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
    [javac] at org.apache.tools.ant.Task.perform(Task.java:348)
    [javac] at org.apache.tools.ant.Target.execute(Target.java:392)
    [javac] at org.apache.tools.ant.Target.performTasks(Target.java:413)
    [javac] at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1399)
    [javac] at org.apache.tools.ant.Project.executeTarget(Project.java:1368)
    [javac] at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java:41)
    [javac] at org.apache.tools.ant.Project.executeTargets(Project.java:1251)
    [javac] at org.apache.tools.ant.Main.runBuild(Main.java:811)
    [javac] at org.apache.tools.ant.Main.startAnt(Main.java:217)
    [javac] at org.apache.tools.ant.launch.Launcher.run(Launcher.java:280)
    [javac] at org.apache.tools.ant.launch.Launcher.main(Launcher.java:109)
    [javac] Caused by: java.lang.NullPointerException: Cannot read field "endKind" because "tag" is null
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.isSelfClosingAllowed(Checker.java:432)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitStartElement(Checker.java:389)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitStartElement(Checker.java:106)
    [javac] at jdk.compiler/com.sun.tools.javac.tree.DCTree$DCStartElement.accept(DCTree.java:862)
    [javac] at jdk.compiler/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:76)
    [javac] at jdk.compiler/com.sun.source.util.DocTreeScanner.scanAndReduce(DocTreeScanner.java:87)
    [javac] at jdk.compiler/com.sun.source.util.DocTreeScanner.scan(DocTreeScanner.java:102)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitDocComment(Checker.java:273)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitDocComment(Checker.java:106)
    [javac] at jdk.compiler/com.sun.tools.javac.tree.DCTree$DCDocComment.accept(DCTree.java:138)
    [javac] at jdk.compiler/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:55)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.scan(Checker.java:234)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$2.visitDecl(DocLint.java:291)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$DeclScanner.visitMethod(DocLint.java:405)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$DeclScanner.visitMethod(DocLint.java:382)
    [javac] at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:933)
    [javac] at jdk.compiler/com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:86)
    [javac] at jdk.compiler/com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:94)
    [javac] at jdk.compiler/com.sun.source.util.TreeScanner.scan(TreeScanner.java:109)
    [javac] at jdk.compiler/com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:117)
    [javac] at jdk.compiler/com.sun.source.util.TreeScanner.visitClass(TreeScanner.java:194)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$DeclScanner.visitClass(DocLint.java:400)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$DeclScanner.visitClass(DocLint.java:382)
    [javac] at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:840)
    [javac] at jdk.compiler/com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:86)
    [javac] at jdk.compiler/com.sun.source.util.TreeScanner.scan(TreeScanner.java:109)
    [javac] at jdk.compiler/com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:117)
    [javac] at jdk.compiler/com.sun.source.util.TreeScanner.visitCompilationUnit(TreeScanner.java:148)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$DeclScanner.visitCompilationUnit(DocLint.java:426)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$DeclScanner.visitCompilationUnit(DocLint.java:382)
    [javac] at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCCompilationUnit.accept(JCTree.java:611)
    [javac] at jdk.compiler/com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:86)
    [javac] at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$3.started(DocLint.java:302)
    [javac] at jdk.compiler/com.sun.tools.javac.api.ClientCodeWrapper$WrappedTaskListener.started(ClientCodeWrapper.java:853)
    [javac] ... 110 more
    [javac] printing javac parameters to: C:\Users\Uwe Schindler\Projects\lucene\lusolr\javac.20210407_134918.args

The relevant command line args are:
-Xdoclint:all -Xdoclint:-missing -Xdoclint:-accessibility -Xdoclint:-html

It happens with the following (invalid) Javadoc comment:

  /**
   * Creates randomized configuration of a specified depth. Simple configuration example:
   *
   * <pre>
   *
   * &lt;dataConfig>
   * <dataSource type="MockDataSource" />
   * &lt;document>
   * &lt;entity name="parent" query="SELECT * FROM parent">
   * &lt;field column="id" />
   * &lt;field column="desc" />
   * &lt;field column="type_s" />
   * &lt;entity child="true" name="parentChild0" query="select * from parentChild0 where parentChild0_parent_id='${parent.id}'">
   * &lt;field column="id" />
   * &lt;field column="desc" />
   * &lt;field column="type_s" />
   * &lt;entity child="true" name="parentChild0Child0" query="select * from parentChild0Child0 where parentChild0Child0_parent_id='${parentChild0.id}'">
   * &lt;field column="id" />
   * &lt;field column="desc" />
   * &lt;field column="type_s" />
   * &lt;/entity>
   * &lt;entity child="true" name="parentChild0Child1" query="select * from parentChild0Child1 where parentChild0Child1_parent_id='${parentChild0.id}'">
   * &lt;field column="id" />
   * &lt;field column="desc" />
   * &lt;field column="type_s" />
   * &lt;/entity>
   * &lt;/entity>
   * &lt;entity child="true" name="parentChild1" query="select * from parentChild1 where parentChild1_parent_id='${parent.id}'">
   * &lt;field column="id" />
   * &lt;field column="desc" />
   * &lt;field column="type_s" />
   * &lt;entity child="true" name="parentChild1Child0" query="select * from parentChild1Child0 where parentChild1Child0_parent_id='${parentChild1.id}'">
   * &lt;field column="id" />
   * &lt;field column="desc" />
   * &lt;field column="type_s" />
   * &lt;/entity>
   * &lt;entity child="true" name="parentChild1Child1" query="select * from parentChild1Child1 where parentChild1Child1_parent_id='${parentChild1.id}'">
   * &lt;field column="id" />
   * &lt;field column="desc" />
   * &lt;field column="type_s" />
   * &lt;/entity>
   * &lt;/entity>
   * &lt;/entity>
   * &lt;/document>
   * &lt;/dataConfig>
   *
   * </pre>
   *
   * Internally configures MockDataSource.
   **/

Please take special care on the following line:

   * <dataSource type="MockDataSource" />

If you escape the XML, it does not cause NPE.