Issue #302: DRAFT: support ReferenceSchema#equals with cyclic schemas

everit-org · Jul 24, 2020 · 13438c9 · 13438c9
1 parent fe1a51c
commit 13438c9
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Showing 4 changed files with 78 additions and 16 deletions.
diff --git a/core/src/main/java/org/everit/json/schema/ReferenceSchema.java b/core/src/main/java/org/everit/json/schema/ReferenceSchema.java
@@ -1,11 +1,13 @@
 package org.everit.json.schema;
 
-import static java.util.Objects.requireNonNull;
+import org.everit.json.schema.internal.EqualsCycleBreaker;
 
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 
+import static java.util.Objects.requireNonNull;
+
 /**
  * This class is used by {@link org.everit.json.schema.loader.SchemaLoader} to resolve JSON pointers
  * during the construction of the schema. This class has been made mutable to permit the loading of
@@ -147,13 +149,17 @@ public boolean equals(Object o) {
                     Objects.equals(unprocessedProperties, that.unprocessedProperties) &&
                     Objects.equals(title, that.title) &&
                     Objects.equals(description, that.description) &&
-                    Objects.equals(referredSchema, that.referredSchema) &&
-                    super.equals(that);
+                    super.equals(that) &&
+                    EqualsCycleBreaker.equalsWithoutCycle(this, that, true, ReferenceSchema::equalsPossiblyCyclic);
         } else {
             return false;
         }
     }
 
+    private boolean equalsPossiblyCyclic(ReferenceSchema that) {
+        return Objects.equals(referredSchema, that.referredSchema);
+    }
+
     @Override
     public int hashCode() {
         return Objects.hash(super.hashCode(), refValue, unprocessedProperties, title, description);

diff --git a/core/src/main/java/org/everit/json/schema/internal/EqualsCycleBreaker.java b/core/src/main/java/org/everit/json/schema/internal/EqualsCycleBreaker.java
@@ -0,0 +1,57 @@
+package org.everit.json.schema.internal;
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.WeakHashMap;
+import java.util.function.BiFunction;
+
+public final class EqualsCycleBreaker
+{
+    private EqualsCycleBreaker()
+    {
+        throw new UnsupportedOperationException();
+    }
+
+    /**
+     * For each invocation of <code>a.equals(b)</code> that uses this class,
+     */
+    private static final ThreadLocal<WeakHashMap<Identity, Set>> ongoingEqualityChecks = ThreadLocal.withInitial(WeakHashMap::new);
+
+    public static <T> boolean equalsWithoutCycle(T self, T other, boolean equalsOnCycle, BiFunction<T, T, Boolean> equalityFunction) {
+        Set<T> localOngoingEqualityChecks = ongoingEqualityChecks.get()
+            .computeIfAbsent(new Identity<>(self), (_k) -> new HashSet<>());
+        if (localOngoingEqualityChecks.add(other)) {
+            try {
+                return equalityFunction.apply(self, other);
+            }
+            finally {
+                localOngoingEqualityChecks.remove(other);
+                if (localOngoingEqualityChecks.isEmpty()) {
+                    ongoingEqualityChecks.remove();
+                }
+            }
+        } else {
+            return equalsOnCycle;
+        }
+    }
+
+    private static class Identity<E> {
+        private final E e;
+
+        public Identity(E e)
+        {
+            this.e = e;
+        }
+
+        public int hashCode() {
+            return System.identityHashCode(e);
+        }
+
+        public boolean equals(Object o) {
+            if (!(o instanceof Identity)) {
+                return false;
+            }
+            return ((Identity<?>) o).e == e;
+        }
+    }
+}
diff --git a/core/src/test/java/org/everit/json/schema/HashCodeRecursionTest.java b/core/src/test/java/org/everit/json/schema/HashCodeRecursionTest.java
@@ -8,7 +8,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 
-import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertEquals;
 
 public class HashCodeRecursionTest
 {
@@ -21,9 +21,10 @@ public void hashCodeShouldNotProduceStackoverflowOnCyclicSchema() throws IOExcep
     @Test
     public void equalsShouldNotProduceStackoverflowOnCyclicSchema() throws IOException
     {
-        Schema cyclic = loadSelfCyclic();
-        Schema cyclicCopy = loadSelfCyclic();
-        cyclic.equals(cyclicCopy);
+        CombinedSchema cyclic = (CombinedSchema) loadSelfCyclic();
+        CombinedSchema cyclicCopy = (CombinedSchema) loadSelfCyclic();
+
+        assertEquals(cyclic, cyclicCopy);
     }
 
     private Schema loadSelfCyclic() throws IOException

diff --git a/core/src/test/java/org/everit/json/schema/ReferenceSchemaTest.java b/core/src/test/java/org/everit/json/schema/ReferenceSchemaTest.java
@@ -15,21 +15,19 @@
  */
 package org.everit.json.schema;
 
-import static java.util.Collections.emptyMap;
-import static org.everit.json.schema.TestSupport.buildWithLocation;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
-
+import com.google.common.collect.ImmutableMap;
+import nl.jqno.equalsverifier.EqualsVerifier;
+import nl.jqno.equalsverifier.Warning;
 import org.everit.json.schema.ReferenceSchema.Builder;
 import org.everit.json.schema.loader.SchemaLoader;
 import org.json.JSONObject;
 import org.junit.Assert;
 import org.junit.Test;
 
-import com.google.common.collect.ImmutableMap;
-
-import nl.jqno.equalsverifier.EqualsVerifier;
-import nl.jqno.equalsverifier.Warning;
+import static java.util.Collections.emptyMap;
+import static org.everit.json.schema.TestSupport.buildWithLocation;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 
 public class ReferenceSchemaTest {