Generic metric reporter for PMD

MetricReporter.java

package net.sourceforge.pmd.lang.metrics.internal;

import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.stream.Collectors;

import net.sourceforge.pmd.RuleContext;
import net.sourceforge.pmd.lang.ast.Node;
import net.sourceforge.pmd.lang.metrics.LanguageMetricsProvider;
import net.sourceforge.pmd.lang.metrics.MetricKey;
import net.sourceforge.pmd.lang.rule.AbstractRule;

public class MetricReporter extends AbstractRule {
    // don't forget to set the language in you ruleset xml
  
    @Override
    public void apply(List<? extends Node> nodes, RuleContext ctx) {

        LanguageMetricsProvider<?, ?> pro = ctx.getLanguageVersion().getLanguageVersionHandler().getLanguageMetricsProvider();

        nodes.stream()
             .flatMap(n -> n.findDescendantsOfType(Node.class).stream())
             // then you can parse the report
             .forEach(n -> allMetrics(pro, n).forEach((k, v) -> addViolationWithMessage(ctx, n, k.name() + " : " + v)));

    }

    private Map<MetricKey<?>, Double> allMetrics(LanguageMetricsProvider<?, ?> provider, Node n) {
        // the map may have some NaN values, when the metric is not supported  
        return provider.computeAllMetricsFor(n)
                       .entrySet()
                       .stream()
                       .filter(it -> !it.getValue().isNaN())
                       .collect(Collectors.toMap(Entry::getKey, Entry::getValue));

    }

}

ruleset.xml

<ruleset name="TODO"
         xmlns="http://pmd.sourceforge.net/ruleset/2.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://pmd.sourceforge.net/ruleset/2.0.0 https://pmd.sourceforge.io/ruleset_2_0_0.xsd">

    <description>
        TODO
    </description>

    <rule name="MetricReporter"
          language="java"
          class="net.sourceforge.pmd.lang.metrics.internal.MetricReporter">
        <description>
            Reports all available metrics
        </description>
    </rule>

</ruleset>