VariableDeclarationUsageDistance throws NPE on empty switch statements

[Vyom-Yadav]

I have read check documentation: https://checkstyle.org/config_coding.html#VariableDeclarationUsageDistance
I have downloaded the latest checkstyle from: https://checkstyle.org/cmdline.html#Download_and_Run
I have executed the cli and showed it below, as cli describes the problem better than 1,000 words

/var/tmp $ javac Test.java

/var/tmp $ cat config.xml

<!DOCTYPE module PUBLIC
        "-//Puppy Crawl//DTD Check Configuration 1.2//EN"
        "http://www.puppycrawl.com/dtds/configuration_1_2.dtd">

<module name="Checker">
  <module name="TreeWalker">
    <module name="VariableDeclarationUsageDistance">
      <property name="validateBetweenScopes" value="true"/>
      <property name="allowedDistance" value="1"/>
    </module>
  </module>
</module>

/var/tmp $ cat Test.java

public class Test {
    void method() {
        int i = -1;
        switch (i) {
        }
    }
}

/var/tmp $ RUN_LOCALE="-Duser.language=en -Duser.country=US"
/var/tmp $ java $RUN_LOCALE -jar checkstyle-10.3.1-all.jar -c config.xml Test.java
Starting audit...
com.puppycrawl.tools.checkstyle.api.CheckstyleException: Exception was thrown while processing Test.java
        at com.puppycrawl.tools.checkstyle.Checker.processFiles(Checker.java:307)
        at com.puppycrawl.tools.checkstyle.Checker.process(Checker.java:224)
        at com.puppycrawl.tools.checkstyle.Main.runCheckstyle(Main.java:407)
        at com.puppycrawl.tools.checkstyle.Main.runCli(Main.java:330)
        at com.puppycrawl.tools.checkstyle.Main.execute(Main.java:189)
        at com.puppycrawl.tools.checkstyle.Main.main(Main.java:126)
Caused by: java.lang.NullPointerException
        at com.puppycrawl.tools.checkstyle.checks.coding.VariableDeclarationUsageDistanceCheck.getFirstNodeInsideSwitchBlock(VariableDeclarationUsageDistanceCheck.java:836)
        at com.puppycrawl.tools.checkstyle.checks.coding.VariableDeclarationUsageDistanceCheck.calculateDistanceBetweenScopes(VariableDeclarationUsageDistanceCheck.java:651)
        at com.puppycrawl.tools.checkstyle.checks.coding.VariableDeclarationUsageDistanceCheck.visitToken(VariableDeclarationUsageDistanceCheck.java:410)
        at com.puppycrawl.tools.checkstyle.TreeWalker.notifyVisit(TreeWalker.java:335)
        at com.puppycrawl.tools.checkstyle.TreeWalker.processIter(TreeWalker.java:406)
        at com.puppycrawl.tools.checkstyle.TreeWalker.walk(TreeWalker.java:273)
        at com.puppycrawl.tools.checkstyle.TreeWalker.processFiltered(TreeWalker.java:154)
        at com.puppycrawl.tools.checkstyle.api.AbstractFileSetCheck.process(AbstractFileSetCheck.java:92)
        at com.puppycrawl.tools.checkstyle.Checker.processFile(Checker.java:333)
        at com.puppycrawl.tools.checkstyle.Checker.processFiles(Checker.java:294)
        ... 5 more
Checkstyle ends with 1 errors.

[stoyanK7]

On it. Documentation on property validateBetweenScopes is weird to me. I suppose we expect no violation here, is that right?

Also, do we expect violation in the following code when using your configuration, i suppose no as well?

public class Test {
    void method() {
        int i = -1;



        switch (i) {
        }
    }
}

[Vyom-Yadav]

No, we do not expect violation in both cases, empty lines do not count in declaration distance. In both cases, the distance between declaration and usage is 0.

[nrmancuso]

Closed via #12052

[Vyom-Yadav]

Awesome work @stoyanK7