mutation: Make `toString()` work with cyclic mutator structures

A new `getDebugString` function is introduced that provides a predicate
as an argument with which implementors can check whether they are part
of a cyclic structure (e.g. a self-referential Protobuf message).

This requires making `SerializingMutator` an abstract class so that an
implementation of `toString` can be provided.

2 files changed, 7 insertions, 3 deletions

diff --git a/src/test/java/com/code_intelligence/jazzer/mutation/combinator/MutatorCombinatorsTest.java b/src/test/java/com/code_intelligence/jazzer/mutation/combinator/MutatorCombinatorsTest.java
index eae088f7..a8424ecb 100644
--- a/src/test/java/com/code_intelligence/jazzer/mutation/combinator/MutatorCombinatorsTest.java
+++ b/src/test/java/com/code_intelligence/jazzer/mutation/combinator/MutatorCombinatorsTest.java
@@ -27,6 +27,7 @@ import static com.code_intelligence.jazzer.mutation.support.TestSupport.nullData
 import static com.google.common.truth.Truth.assertThat;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
+import com.code_intelligence.jazzer.mutation.api.Debuggable;
 import com.code_intelligence.jazzer.mutation.api.InPlaceMutator;
 import com.code_intelligence.jazzer.mutation.api.PseudoRandom;
 import com.code_intelligence.jazzer.mutation.api.SerializingMutator;
@@ -35,6 +36,7 @@ import java.io.DataInputStream;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.function.Predicate;
 import org.junit.jupiter.api.Test;
 
 class MutatorCombinatorsTest {
@@ -77,7 +79,7 @@ class MutatorCombinatorsTest {
       }
 
       @Override
-      public String toString() {
+      public String toDebugString(Predicate<Debuggable> isInCycle) {
         return "List<Integer>";
       }
     });
@@ -120,7 +122,7 @@ class MutatorCombinatorsTest {
           }
 
           @Override
-          public String toString() {
+          public String toDebugString(Predicate<Debuggable> isInCycle) {
             return "List<Integer>";
           }
         });
diff --git a/src/test/java/com/code_intelligence/jazzer/mutation/support/TestSupport.java b/src/test/java/com/code_intelligence/jazzer/mutation/support/TestSupport.java
index 9a4c1572..c7744cec 100644
--- a/src/test/java/com/code_intelligence/jazzer/mutation/support/TestSupport.java
+++ b/src/test/java/com/code_intelligence/jazzer/mutation/support/TestSupport.java
@@ -21,6 +21,7 @@ import static com.google.common.truth.Truth.assertThat;
 import static java.util.Arrays.stream;
 import static java.util.stream.Collectors.toCollection;
 
+import com.code_intelligence.jazzer.mutation.api.Debuggable;
 import com.code_intelligence.jazzer.mutation.api.PseudoRandom;
 import com.code_intelligence.jazzer.mutation.api.SerializingMutator;
 import com.code_intelligence.jazzer.mutation.engine.SeededPseudoRandom;
@@ -32,6 +33,7 @@ import java.io.OutputStream;
 import java.util.ArrayDeque;
 import java.util.Queue;
 import java.util.function.Function;
+import java.util.function.Predicate;
 
 public final class TestSupport {
   private static final DataOutputStream nullDataOutputStream =
@@ -88,7 +90,7 @@ public final class TestSupport {
       }
 
       @Override
-      public String toString() {
+      public String toDebugString(Predicate<Debuggable> isInCycle) {
         if (initialValue == null) {
           return "null";
         }