Fix module name detection for headless sessions (#7807)

dd-java-agent/agent-ci-visibility/src/main/java/datadog/trace/civisibility/CiVisibilityRepoServices.java

@@ -89,18 +89,18 @@ public class CiVisibilityRepoServices {
     }
   }
 
-  private static String getModuleName(Config config, Path path, CIInfo ciInfo) {
+  static String getModuleName(Config config, Path path, CIInfo ciInfo) {
     // if parent process is instrumented, it will provide build system's module name
     String parentModuleName = config.getCiVisibilityModuleName();
     if (parentModuleName != null) {
       return parentModuleName;
     }
     String repoRoot = ciInfo.getNormalizedCiWorkspace();
-    if (repoRoot != null
-        && path.startsWith(repoRoot)
-        // module name cannot be empty
-        && !path.toString().equals(repoRoot)) {
-      return Paths.get(repoRoot).relativize(path).toString();
+    if (repoRoot != null && path.startsWith(repoRoot)) {
+      String relativePath = Paths.get(repoRoot).relativize(path).toString();
+      if (!relativePath.isEmpty()) {
+        return relativePath;
+      }
     }
     return config.getServiceName();
   }

dd-java-agent/agent-ci-visibility/src/test/groovy/datadog/trace/civisibility/CiVisibilityRepoServicesTest.groovy

@@ -0,0 +1,33 @@
+package datadog.trace.civisibility
+
+
+import datadog.trace.api.Config
+import datadog.trace.civisibility.ci.CIInfo
+import spock.lang.Specification
+
+import java.nio.file.Paths
+
+class CiVisibilityRepoServicesTest extends Specification {
+
+  def "test get parent module name: #parentModuleName, #repoSubFolder, #serviceName"() {
+    given:
+    def config = Stub(Config)
+    config.getCiVisibilityModuleName() >> parentModuleName
+    config.getServiceName() >> serviceName
+
+    def repoRoot = "/path/to/repo/root/"
+    def path = Paths.get(repoRoot + repoSubFolder)
+
+    def ciInfo = Stub(CIInfo)
+    ciInfo.getNormalizedCiWorkspace() >> repoRoot
+
+    expect:
+    CiVisibilityRepoServices.getModuleName(config, path, ciInfo) == moduleName
+
+    where:
+    parentModuleName | repoSubFolder  | serviceName    | moduleName
+    "parent-module"  | "child-module" | "service-name" | "parent-module"
+    null             | "child-module" | "service-name" | "child-module"
+    null             | ""             | "service-name" | "service-name"
+  }
+}