Fix stackoverflow issue related to pymap hashcode computation

src/main/java/com/hubspot/jinjava/objects/collections/PyMap.java

@@ -2,6 +2,10 @@
 
 import com.google.common.collect.ForwardingMap;
 import com.hubspot.jinjava.objects.PyWrapper;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.ListIterator;
 import java.util.Map;
 import java.util.Set;
 
@@ -62,9 +66,39 @@ public void putAll(Map<? extends String, ? extends Object> m) {
   @Override
   public int hashCode() {
     int h = 0;
-    for (Entry<String, Object> entry : map.entrySet()) {
-      if (entry.getValue() != map && entry.getValue() != this) {
-        h += entry.hashCode();
+    List<Object> valueList = new ArrayList<>(map.entrySet());
+    ListIterator<Object> valueIterator = valueList.listIterator();
+    Set<Integer> visited = new HashSet<>();
+    while (valueIterator.hasNext()) {
+      Object next = valueIterator.next();
+      int code = System.identityHashCode(next);
+      if (visited.contains(code)) {
+        continue;
+      } else {
+        visited.add(code);
+      }
+      if (next instanceof Entry) {
+        Entry nextEntry = (Entry) next;
+        if (nextEntry.getKey() != null) {
+          h += nextEntry.getKey().hashCode();
+        }
+        valueIterator.add(nextEntry.getValue());
+        valueIterator.previous();
+      } else if (next instanceof Iterable) {
+        for (Object o : (Iterable) next) {
+          valueIterator.add(o);
+          valueIterator.previous();
+        }
+      } else if (next instanceof Map) {
+        ((Map) next).entrySet()
+          .forEach(
+            e -> {
+              valueIterator.add(e);
+              valueIterator.previous();
+            }
+          );
+      } else if (next != null) {
+        h += next.hashCode();
       }
     }
     return h;

src/test/java/com/hubspot/jinjava/objects/collections/PyMapTest.java

@@ -3,13 +3,15 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
+import com.google.common.collect.ImmutableList;
 import com.hubspot.jinjava.BaseJinjavaTest;
 import com.hubspot.jinjava.Jinjava;
 import com.hubspot.jinjava.JinjavaConfig;
 import com.hubspot.jinjava.LegacyOverrides;
 import com.hubspot.jinjava.interpret.IndexOutOfRangeException;
 import com.hubspot.jinjava.interpret.RenderResult;
 import com.hubspot.jinjava.interpret.TemplateError;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import org.junit.Test;
@@ -367,4 +369,61 @@ public void itUpdatesKeysWithVariableName() {
       )
       .isEqualTo("value2");
   }
+
+  @Test
+  public void itComputesHashCodeWhenContainedWithinItself() {
+    PyMap map = new PyMap(new HashMap<>());
+    map.put("map1key1", "value1");
+
+    PyMap map2 = new PyMap(new HashMap<>());
+    map2.put("map2key1", map);
+
+    map.put("map1key2", map2);
+
+    assertThat(map.hashCode()).isEqualTo(-413943561);
+  }
+
+  @Test
+  public void itComputesHashCodeWhenContainedWithinItselfWithFurtherEntries() {
+    PyMap map = new PyMap(new HashMap<>());
+    map.put("map1key1", "value1");
+
+    PyMap map2 = new PyMap(new HashMap<>());
+    map2.put("map2key1", map);
+
+    map.put("map1key2", map2);
+
+    int originalHashCode = map.hashCode();
+    map2.put("newKey", "newValue");
+    int newHashCode = map.hashCode();
+    assertThat(originalHashCode).isNotEqualTo(newHashCode);
+  }
+
+  @Test
+  public void itComputesHashCodeWhenContainedWithinItselfInsideList() {
+    PyMap map = new PyMap(new HashMap<>());
+    map.put("map1key1", "value1");
+
+    PyMap map2 = new PyMap(new HashMap<>());
+    map2.put("map2key1", map);
+
+    map.put("map1key2", new PyList(ImmutableList.of((map2))));
+
+    assertThat(map.hashCode()).isEqualTo(-413943561);
+  }
+
+  @Test
+  public void itComputesHashCodeWithNullKeysAndValues() {
+    PyMap map = new PyMap(new HashMap<>());
+    map.put(null, "value1");
+
+    PyMap map2 = new PyMap(new HashMap<>());
+    map2.put("map2key1", map);
+
+    PyList list = new PyList(new ArrayList<>());
+    list.add(null);
+    map.put("map1key2", new PyList(list));
+
+    assertThat(map.hashCode()).isEqualTo(-687497624);
+  }
 }