Use isResolvableObject instead of contains before trying to build

hashcode

1. using `contains` can cause a StackOverflowError
2. If the depth grows very deep, running hashCode can be quite slow,
   using isResolvableObject will break out before going into too much
   depth and we won't use hashCode

In cases where we can't use the hashCode of such objects, we just aren't
able to check for changes to them

Author: jasmith-hs

src/main/java/com/hubspot/jinjava/util/EagerContextWatcher.java

@@ -123,8 +123,7 @@ private static Map<String, String> getInitiallyResolvedAsStrings(
           ? entrySet
           : interpreter.getContext().getCombinedScope().entrySet()).stream()
         .filter(entry -> initiallyResolvedHashes.containsKey(entry.getKey()))
-        .filter(entry ->
-          EagerExpressionResolver.isResolvableObject(entry.getValue(), 4, 400) // TODO make this configurable
+        .filter(entry -> isResolvableForContextReverting(entry.getValue()) // TODO make this configurable
         );
     entryStream.forEach(entry ->
       cacheRevertibleObject(
@@ -392,15 +391,19 @@ private static Object getObjectOrHashCode(Object o) {
       o = ((LazyExpression) o).get();
     }
 
-    if (o instanceof PyList && !((PyList) o).toList().contains(o)) {
+    if (o instanceof PyList && isResolvableForContextReverting(o)) {
       return o.hashCode();
     }
-    if (o instanceof PyMap && !((PyMap) o).toMap().containsValue(o)) {
+    if (o instanceof PyMap && isResolvableForContextReverting(o)) {
       return o.hashCode() + ((PyMap) o).keySet().hashCode();
     }
     return o;
   }
 
+  private static boolean isResolvableForContextReverting(Object o) {
+    return EagerExpressionResolver.isResolvableObject(o, 4, 400);
+  }
+
   public static class EagerChildContextConfig {
 
     private final boolean takeNewValue;

src/test/java/com/hubspot/jinjava/EagerTest.java

@@ -1740,4 +1740,11 @@ public void itHandlesModifiedIncludePathSecondPass() {
       "handles-modified-include-path/test.expected"
     );
   }
+
+  @Test
+  public void itDoesNotStackOverflowTryingToBuildHashcode() {
+    expectedTemplateInterpreter.assertExpectedOutput(
+      "does-not-stack-overflow-trying-to-build-hashcode/test"
+    );
+  }
 }

src/test/resources/eager/does-not-stack-overflow-trying-to-build-hashcode/test.expected.jinja

@@ -0,0 +1,3 @@
+{% for i in deferred %}
+hey
+{% endfor %}

src/test/resources/eager/does-not-stack-overflow-trying-to-build-hashcode/test.jinja

@@ -0,0 +1,12 @@
+{% set l1000_1 = [] %}
+{% set l1000_2 = [] %}
+{% set l1000_3 = [] %}
+
+{% do l1000_1.append(l1000_2) %}
+{% do l1000_2.append(l1000_3) %}
+{% do l1000_3.append(l1000_1) %}
+
+
+{% for i in deferred %}
+{{ 'hey' }}
+{% endfor %}