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The Kamon Instrumentation Agent

There is a newer version: 1.0.18

package kanela.agent.util.classloader;

import lombok.val;
import net.bytebuddy.matcher.ElementMatcher;

import java.net.URL;
import java.net.URLClassLoader;
import java.util.Collections;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

public class ScalaCompilerClassLoaderMatcher extends ElementMatcher.Junction.AbstractBase {

  @Override
  public boolean matches(ClassLoader classLoader) {
    return isScalaCompilerClassLoader(classLoader);
  }

  private static Set knownScalaClassLoaders = Collections.newSetFromMap(new ConcurrentHashMap<>());

  /**
   * Tries to determine whether the ClassLoader causing errors belongs to the Scala Compiler on SBT. Since there is
   * no special naming or treatment of this particular ClassLoader it is impossible to filter it out from the
   * instrumentation process, but given that the jars found on it are quite particular (the compiler and jline) we can
   * assume that any instrumentation errors happening on that ClassLoader should be dismissed.
   *
   * We are doing this check here instead of using a ClassLoaderNameMatcher because this is a relatively expensive
   * check which might only be necessary in a few cases, so we rather filter the error than putting the burden of this
   * check on every single class load.
   */
  public static boolean isScalaCompilerClassLoader(ClassLoader classLoader) {
    if(classLoader instanceof URLClassLoader) {
      if(knownScalaClassLoaders.contains(classLoader))
        return true;
      else {
        val urlClassLoader = (URLClassLoader) classLoader;
        boolean foundScalaCompiler = false;
        boolean foundJLine = false;

        for (URL url : urlClassLoader.getURLs()) {
          if (url.getFile().contains("scala-compiler"))
            foundScalaCompiler = true;
          if (url.getFile().contains("jline"))
            foundJLine = true;
        }

        val isScalaCompiler = foundScalaCompiler && foundJLine;
        if (isScalaCompiler)
          knownScalaClassLoaders.add(classLoader);

        return isScalaCompiler;
      }
    } else return false;
  }

}