HiddenField false positive on inner records

[fprochazka]

Link to check documentation: https://checkstyle.sourceforge.io/checks/coding/hiddenfield.html

/var/tmp $ cat config.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
    "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
    "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
<module name="Checker">
    <property name="charset" value="UTF-8"/>

    <module name="TreeWalker">
        <module name="HiddenField">
            <property name="ignoreConstructorParameter" value="true"/>
            <property name="setterCanReturnItsClass" value="true"/>
            <property name="ignoreSetter" value="true"/>
        </module>
    </module>
</module>

/var/tmp $ cat YOUR_FILE.java

import java.time.Clock;
import java.time.Instant;

class Scratch
{

    private final Clock clock;

    public Scratch(final Clock clock)
    {
        this.clock = clock;
    }

    public void test()
    {
        var state = new State("val", Instant.now().minusSeconds(1));
        var is = state.isFresh(clock);
        System.out.println(is);
    }

    public record State(
        String token,
        Instant expiresAt
    )
    {

        public boolean isFresh(final Clock clock) // violation
        {
            return Instant.now(clock).isBefore(expiresAt);
        }

    }

}

/var/tmp $ RUN_LOCALE="-Duser.language=en -Duser.country=US"
/var/tmp $ java $RUN_LOCALE -jar ./checkstyle-10.12.4-all.jar -c ./config.xml scratch_617.java                                                                                                                      254 ↵
Starting audit...
[ERROR] scratch_617.java:27:44: 'clock' hides a field. [HiddenField]
Audit done.
Checkstyle ends with 1 errors.

---

Describe what you expect in detail.

Adding static to the inner record fixes the false positive, but records don't share this of outer class, so the check is wrong in this case, because the static is AFAIK implicit.

[nrmancuso]

Some comparisons with inner classes also:

➜  src cat config.xml 
<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
    "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
    "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
<module name="Checker">
    <property name="charset" value="UTF-8"/>

    <module name="TreeWalker">
        <module name="HiddenField">
            <property name="ignoreConstructorParameter" value="true"/>
            <property name="setterCanReturnItsClass" value="true"/>
            <property name="ignoreSetter" value="true"/>
        </module>
    </module>
</module>
➜  src cat Test.java 
public class Test {
    private final int x;

    public Test(int x) {
        this.x = x;
    }

    // inner record is implicitly static, should be treated
    // the same as R2
    public record R1() {
        public void m(int x) {} // unexpected violation
    }

    public static record R2() {
        public void m(int x) {} // no violation expected
    }

    // static class, should be treated the same as R2
    public static class C1 {
        public void m(int x) {} // no violation expected
    }

    // non-static class, should have a violation
    public class C2 {
        public void m(int x) {} // violation
    }
}
➜  src javac Test.java
➜  src java -jar checkstyle-10.12.1-all.jar -c config.xml Test.java
Starting audit...
[ERROR] /home/nick/IdeaProjects/tester/src/Test.java:11:27: 'x' hides a field. [HiddenField]
[ERROR] /home/nick/IdeaProjects/tester/src/Test.java:25:27: 'x' hides a field. [HiddenField]
Audit done.
Checkstyle ends with 2 errors.

Issue is approved, @fprochazka please feel free to send a PR

[Kevin222004]

@romani I think this issue needs to be closed know

[nrmancuso]

Closed via #14128

[nrmancuso]

@Kevin222004 issue will be automatically closed if you do “Closes #….” in the PR description.