false positive invalid tag JavadocType

[Machine-Maker]

https://checkstyle.org/checks/javadoc/javadoctype.html#JavadocType

/var/tmp $ javac Test.java
# success

/var/tmp $ cat checkstyle.xml
<!DOCTYPE module PUBLIC
    "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
    "https://checkstyle.org/dtds/configuration_1_3.dtd">

<module name="Checker">
  <module name="TreeWalker">
    <module name="JavadocType"/>
  </module>
</module>

/var/tmp $ cat Test.java
/**
 * <pre>{@code
 * @Internal
 * class Other {
 *   @Nullable String test(String param) {
 *   }
 * }
 * }</pre>
 */
public class Test {
  public void test(String param) {
  }
}

/var/tmp $ java -jar checkstyle-10.21.0-all.jar -c checkstyle.xml test.java
Starting audit...
[ERROR] /Users/jake/Projects/Java/checkstyle-test/Test.java:3:4: Unknown tag 'Internal'. [JavadocType]
[ERROR] /Users/jake/Projects/Java/checkstyle-test/Test.java:5:6: Unknown tag 'Nullable'. [JavadocType]
Audit done.
Checkstyle ends with 2 errors.

---

@Internal and @Nullable should not be reported as an unknown tag. It is inside a valid pre/code tag combo which is displayed correctly by the javadoc tool. You can see the rendered html below.

[romani]

All logic is at https://github.com/checkstyle/checkstyle/blob/master/src/main/java/com/puppycrawl/tools/checkstyle/checks/javadoc/JavadocTypeCheck.java#L154

It is Check, old Check, that doesn't use AST.
So fixing issue on it might be not easy.

But issue is valid, no violations are expected.

[Machine-Maker]

For anyone else who finds this, I kinda solved it with the following suppression filter

    <module name="SuppressionSingleFilter">
        <property name="checks" value="Javadoc(Method|Type)"/>
        <!--[A-Z].* check is for java annotations inside code blocks inside javadocs-->
        <property name="message" value="^Unknown tag '(${custom_javadoc_tags}|[A-Z].*)'.$"/>
    </module>

${custom_javadocs_tags} is an injected property with all the custom javadoc tags registered with the javadoc tool in gradle (in my case, just apiNote). But after that, the [A-Z].* regex, just suppresses warnings if the first letter of the tag is capital (which isn't the case for any real javadoc tag and is the case for most (normal) java annotations).

[XN137]

hitting a similar issue after upgrading from 10.20.0 to 10.21.1:
#14573 (comment)

it seems like content inside <pre>..</pre> isnt ignored (but should be?).

[romani]

It should be.
Main rule: if javadoc passed/generated by jdk tool javadoc , so checkstyle should support such javadoc also.