Remove static inherited fields collection

To avoid premature class loading and potential LinkageError we are not
collecting the static inherited fields of a class

Author: jpbempel

dd-java-agent/agent-debugger/src/main/java/com/datadog/debugger/instrumentation/CapturedContextInstrumentor.java

@@ -1,6 +1,5 @@
 package com.datadog.debugger.instrumentation;
 
-import static com.datadog.debugger.instrumentation.ASMHelper.extractSuperClass;
 import static com.datadog.debugger.instrumentation.ASMHelper.getStatic;
 import static com.datadog.debugger.instrumentation.ASMHelper.invokeConstructor;
 import static com.datadog.debugger.instrumentation.ASMHelper.invokeStatic;
@@ -1136,51 +1135,13 @@ private static List<FieldNode> extractStaticFields(
         }
       }
     }
-    if (!Config.get().isDynamicInstrumentationInstrumentTheWorld()) {
-      // Collects inherited static fields only if the ITW mode is not enabled
-      // because it can lead to LinkageError: attempted duplicate class definition
-      // for example, when a probe is located in method overridden in enum element
-      addInheritedStaticFields(classNode, classLoader, limits, results, fieldCount);
-    }
+    // Collecting inherited static fields is problematic because it some cases can lead to
+    // LinkageError: attempted duplicate class definition
+    // as we force to load a class to get the static fields in a different order than the JVM
+    // for example, when a probe is located in method overridden in enum element
     return results;
   }
 
-  private static void addInheritedStaticFields(
-      ClassNode classNode,
-      ClassLoader classLoader,
-      Limits limits,
-      List<FieldNode> results,
-      int fieldCount) {
-    String superClassName = extractSuperClass(classNode);
-    while (!superClassName.equals(Object.class.getTypeName())) {
-      Class<?> clazz;
-      try {
-        clazz = Class.forName(superClassName, false, classLoader);
-      } catch (ClassNotFoundException ex) {
-        break;
-      }
-      try {
-        for (Field field : clazz.getDeclaredFields()) {
-          if (isStaticField(field) && !isFinalField(field)) {
-            String desc = Type.getDescriptor(field.getType());
-            FieldNode fieldNode =
-                new FieldNode(field.getModifiers(), field.getName(), desc, null, field);
-            results.add(fieldNode);
-            LOGGER.debug("Adding static inherited field {}", fieldNode.name);
-            fieldCount++;
-            if (fieldCount > limits.maxFieldCount) {
-              return;
-            }
-          }
-        }
-      } catch (ClassCircularityError ex) {
-        break;
-      }
-      clazz = clazz.getSuperclass();
-      superClassName = clazz.getTypeName();
-    }
-  }
-
   private int declareContextVar(InsnList insnList) {
     int var = newVar(CAPTURED_CONTEXT_TYPE);
     getStatic(insnList, CAPTURED_CONTEXT_TYPE, "EMPTY_CAPTURING_CONTEXT");

dd-java-agent/agent-debugger/src/test/java/com/datadog/debugger/agent/CapturedSnapshotTest.java

@@ -1611,12 +1611,9 @@ public void staticInheritedFields() throws IOException, URISyntaxException {
     Snapshot snapshot = assertOneSnapshot(listener);
     Map<String, CapturedContext.CapturedValue> staticFields =
         snapshot.getCaptures().getReturn().getStaticFields();
-    assertEquals(7, staticFields.size());
+    // inherited static fields are not collected
+    assertEquals(2, staticFields.size());
     assertEquals("barfoo", MoshiSnapshotTestHelper.getValue(staticFields.get("strValue")));
-    assertEquals("48", MoshiSnapshotTestHelper.getValue(staticFields.get("intValue")));
-    assertEquals("6.28", MoshiSnapshotTestHelper.getValue(staticFields.get("doubleValue")));
-    assertEquals("[1, 2, 3, 4]", MoshiSnapshotTestHelper.getValue(staticFields.get("longValues")));
-    assertEquals("[foo, bar]", MoshiSnapshotTestHelper.getValue(staticFields.get("strValues")));
   }
 
   @Test