[java] UnnecessaryImport false positive for on-demand imports

[pzygielo]

Affects PMD Version:
6.25 6.34.0 (this ticket was originally for UnusedImports, replaced by UnnecessaryImport)

Rule:
UnnecessaryImports

Description:
Used IMO star-import reported as

[INFO] PMD Failure: m.U:3 Rule:UnusedImports Priority:4 Avoid unused imports such as 'p'.

Code Sample demonstrating the issue:
maven project with:

package p;

public class C {
  final public static String V = "";
}

package m;

import p.*;

public class U {
  private void g() {
    String k = C.V;
  }
}

Expected outcome:
No violation reported, as p.C.V is resolved from p.*.

• Does PMD report a violation, where there shouldn't be one? -> false-positive
  Yes it does.

• Is PMD missing to report a violation, where there should be one? -> false-negative
  No.

Running PMD through:
maven

Similar open issues, but reported for JavaDoc usage of import, while I observe it with code

• [java] UnusedImports false positive for on-demand imports in JavaDoc #2304
• [java] UnusedImports: False positive if nested interface is referenced in javadoc #2001
• [java] UnusedImports false positive for multiline @link Javadoc #1639

Similar and closed

• [java] UnusedImports: False positive if wildcard is used and only static methods #2016 - delivered with 6.20.0
  But with 6.20.0 I also experience violation in my case.

It's possible I'm doing something wrong.

[pzygielo]

I'm afraid the new, replacement UnnecessaryImport rule reports the same FP.

[jonybuzz]

Still happening for this config:

...
    <properties>
        <java.version>11</java.version>
        <pmdVersion>6.41.0</pmdVersion>
    </properties>
    <build>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-pmd-plugin</artifactId>
                <version>3.15.0</version>
                <executions>
                    <execution>
                        <id>pmd-while-compiling</id>
                        <phase>validate</phase>
                        <goals>
                            <goal>check</goal>
                        </goals>
                        <configuration>
                            <printFailingErrors>true</printFailingErrors>
                        </configuration>
                    </execution>
                </executions>
                <dependencies>
                    <dependency>
                        <groupId>net.sourceforge.pmd</groupId>
                        <artifactId>pmd-core</artifactId>
                        <version>${pmdVersion}</version>
                    </dependency>
                    <dependency>
                        <groupId>net.sourceforge.pmd</groupId>
                        <artifactId>pmd-java</artifactId>
                        <version>${pmdVersion}</version>
                    </dependency>
                    <dependency>
                        <groupId>net.sourceforge.pmd</groupId>
                        <artifactId>pmd-javascript</artifactId>
                        <version>${pmdVersion}</version>
                    </dependency>
                    <dependency>
                        <groupId>net.sourceforge.pmd</groupId>
                        <artifactId>pmd-jsp</artifactId>
                        <version>${pmdVersion}</version>
                    </dependency>
                </dependencies>
            </plugin>
    </build>
...

[oowekyala]

@jonybuzz Can you please provide a code example? We have a passing regression test for this issue in our sources...