Fix source path calculation for classes in default package (#6783)

dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/coverage/instrumentation/CoverageInstrumentationFilter.java

@@ -13,6 +13,10 @@ public CoverageInstrumentationFilter(String[] includedPackages, String[] exclude
 
   @Override
   public boolean test(String className) {
+    if (!className.contains("/")) {
+      // always include classes in default package
+      return true;
+    }
     for (String excludedPackage : excludedPackages) {
       if (className.startsWith(excludedPackage)) {
         return false;

dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/source/index/PackageResolver.java

@@ -2,7 +2,10 @@
 
 import java.io.IOException;
 import java.nio.file.Path;
+import javax.annotation.Nullable;
 
 public interface PackageResolver {
+  /** @return the package path or <code>null</code> if the file is in the default package */
+  @Nullable
   Path getPackage(Path sourceFile) throws IOException;
 }

dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/source/index/PackageResolverImpl.java

@@ -7,6 +7,7 @@
 import java.nio.file.Files;
 import java.nio.file.InvalidPathException;
 import java.nio.file.Path;
+import javax.annotation.Nullable;
 
 public class PackageResolverImpl implements PackageResolver {
 
@@ -26,7 +27,10 @@ public PackageResolverImpl(FileSystem fileSystem) {
    * <p>It simply looks for a line, that contains the <code>package</code> keyword and extracts the
    * part that goes after it and until the nearest <code>;</code> character, then verifies that the
    * extracted part looks plausible by checking the actual file path.
+   *
+   * @return the package path or <code>null</code> if the file is in the default package
    */
+  @Nullable
   @Override
   public Path getPackage(Path sourceFile) throws IOException {
     Path folder = sourceFile.getParent();
@@ -65,6 +69,6 @@ public Path getPackage(Path sourceFile) throws IOException {
     }
 
     // apparently there is no package declaration - class is located in the default package
-    return fileSystem.getPath("");
+    return null;
   }
 }

dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/source/index/RepoIndexBuilder.java

@@ -177,8 +177,12 @@ private Path getSourceRoot(Path file) throws IOException {
       } else if (!sourceType.isResource()) {
         indexingStats.sourceFilesVisited++;
         Path packagePath = packageResolver.getPackage(file);
-        packageTree.add(packagePath);
-        return getSourceRoot(file, packagePath);
+        if (packagePath != null) {
+          packageTree.add(packagePath);
+          return getSourceRoot(file, packagePath);
+        } else {
+          return file.getParent();
+        }
 
       } else {
         indexingStats.resourceFilesVisited++;

dd-java-agent/agent-ci-visibility/src/test/groovy/datadog/trace/civisibility/source/index/PackageResolverImplTest.groovy

@@ -21,11 +21,11 @@ class PackageResolverImplTest extends Specification {
     def packagePath = packageResolver.getPackage(javaFilePath)
 
     then:
-    packagePath == fileSystem.getPath(expectedPackageName)
+    packagePath == (expectedPackageName != null ? fileSystem.getPath(expectedPackageName) : null)
 
     where:
     path                             | contents                                      | expectedPackageName
-    "/root/src/MyClass.java"         | CLASS_IN_DEFAULT_PACKAGE                      | ""
+    "/root/src/MyClass.java"         | CLASS_IN_DEFAULT_PACKAGE                      | null
     "/root/src/foo/bar/MyClass.java" | CLASS_IN_FOO_BAR_PACKAGE                      | "foo/bar"
     "/root/src/foo/bar/MyClass.java" | BLANK_LINES_BEFORE_PACKAGE                    | "foo/bar"
     "/root/src/foo/bar/MyClass.java" | SPACES_BEFORE_PACKAGE                         | "foo/bar"