[MCHECKSTYLE-377] Violations or exceptions when using "external" FQCNs in @throws after upgrade to 3.1.0

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 3.1.0

Environment

Apache Maven 3.6.1 (d66c9c0b3152b2e69ee9bac180bb8fcc8e6af555; 2019-04-04T21:00:29+02:00)
Java version: 1.8.0_202, vendor: Oracle Corporation
Default locale: de_DE, platform encoding: Cp1252
OS name: "windows 10", version: "10.0", arch: "amd64", family: "windows"

• Assignee: Unassigned
• Reporter: Falko Modler
• Created: 23/May/19 10:18
• Updated: 04/Jun/20 12:15
• Resolved: 04/Jun/20 12:15

Description

I started to see strange violations and even exceptions after upgrading checkstyle-plugin from 3.0.0 and 3.1.0. Please note that I pinned Checkstyle to 8.7, so the Checkstyle version itself did not change in my setup.

The problem boils down to Checkstyle not being able anymore to load classes that reside in dependencies (= not im the same project as the checked class) when using fully qualified class names in @throws tags, e.g.:

    /**
     * Foo.
     * @throws some.other.project.SomeException some exception.
     */
    public void foo() throws SomeException {
        // ...
    }

Please note that the actual throws declaration does not use the fully qualified class name.
While this might be an inconsistent/non DRY approach, it is not forbidden by JavaDoc or the compiler.

In one case (where the exception resides in an external dependency), this resulted in a violation:

JavadocMethod: Expected @throws tag for 'SomeException'.

In another case (where the exception resides in the same module but implements an interface that resides in another module of the project being built), this resulted in an exception:

[...]
Caused by: java.lang.NoClassDefFoundError: some/project/othermodule/SomeInterface
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:468)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:74)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:369)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:363)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:362)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:348)
        at com.puppycrawl.tools.checkstyle.checks.javadoc.ClassResolver.safeLoad(ClassResolver.java:216)
        at com.puppycrawl.tools.checkstyle.checks.javadoc.ClassResolver.resolve(ClassResolver.java:95)
        at com.puppycrawl.tools.checkstyle.checks.javadoc.AbstractTypeAwareCheck.resolveClass(AbstractTypeAwareCheck.java:241)
        at com.puppycrawl.tools.checkstyle.checks.javadoc.AbstractTypeAwareCheck.tryLoadClass(AbstractTypeAwareCheck.java:258)
        at com.puppycrawl.tools.checkstyle.checks.javadoc.AbstractTypeAwareCheck$RegularClass.getClazz(AbstractTypeAwareCheck.java:467)
        at com.puppycrawl.tools.checkstyle.checks.javadoc.JavadocMethodCheck.checkThrowsTags(JavadocMethodCheck.java:909)
        at com.puppycrawl.tools.checkstyle.checks.javadoc.JavadocMethodCheck.checkComment(JavadocMethodCheck.java:503)
        at com.puppycrawl.tools.checkstyle.checks.javadoc.JavadocMethodCheck.processAST(JavadocMethodCheck.java:357)
        at com.puppycrawl.tools.checkstyle.checks.javadoc.AbstractTypeAwareCheck.visitToken(AbstractTypeAwareCheck.java:157)
        at com.puppycrawl.tools.checkstyle.TreeWalker.notifyVisit(TreeWalker.java:423)
        at com.puppycrawl.tools.checkstyle.TreeWalker.processIter(TreeWalker.java:579)
        at com.puppycrawl.tools.checkstyle.TreeWalker.walk(TreeWalker.java:363)
        at com.puppycrawl.tools.checkstyle.TreeWalker.processFiltered(TreeWalker.java:208)
        at com.puppycrawl.tools.checkstyle.api.AbstractFileSetCheck.process(AbstractFileSetCheck.java:83)
        at com.puppycrawl.tools.checkstyle.Checker.processFile(Checker.java:319)
        at com.puppycrawl.tools.checkstyle.Checker.processFiles(Checker.java:289)
        ... 25 more
Caused by: java.lang.ClassNotFoundException: some.project.othermodule.SomeInterface
        at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        ... 54 more

I guess this is caused by MCHECKSTYLE-353 (which does improve runtime a lot when checkstyle:check is invoked explicitly).

Workaround: Don't use fully qualified exception class names in @throws.

PS: This might actually be a shortcomming in Checkstyle itself and it also might affect more than just @throws.

Issue Links

• is caused by: MCHECKSTYLE-353 Don't resolve any dependencies