From 624923ec7ca88fccda69de7348d49fa3a0b6b49c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20J=C3=A4ckle?= <thomas.jaeckle@beyonnex.io>
Date: Wed, 29 Nov 2023 20:36:07 +0100
Subject: [PATCH] #1826 fix JsonFieldSelectorTrie logic for objects and parts
 of those objects both being included in selected fields

---
 .../ditto/json/JsonFieldSelectorTrie.java     | 16 +++++++++-
 .../ditto/json/JsonFieldSelectorTrieTest.java | 30 +++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/json/src/main/java/org/eclipse/ditto/json/JsonFieldSelectorTrie.java b/json/src/main/java/org/eclipse/ditto/json/JsonFieldSelectorTrie.java
index 622558d3dd..eb188195a5 100644
--- a/json/src/main/java/org/eclipse/ditto/json/JsonFieldSelectorTrie.java
+++ b/json/src/main/java/org/eclipse/ditto/json/JsonFieldSelectorTrie.java
@@ -100,7 +100,21 @@ private JsonFieldSelectorTrie addJsonKeyIterator(final Iterator<JsonKey> iterato
         if (iterator.hasNext()) {
             final JsonKey key = iterator.next();
             children.compute(key, (theKey, theChild) -> {
-                final JsonFieldSelectorTrie child = theChild != null ? theChild : new JsonFieldSelectorTrie();
+                final JsonFieldSelectorTrie child;
+                if (theChild != null) {
+                    if (iterator.hasNext()) {
+                        if (theChild.children.isEmpty()) {
+                            return theChild;
+                        } else {
+                            child = theChild;
+                        }
+                    } else {
+                        child = new JsonFieldSelectorTrie();
+                    }
+                } else {
+                    child = new JsonFieldSelectorTrie();
+                }
+
                 return child.addJsonKeyIterator(iterator);
             });
         }
diff --git a/json/src/test/java/org/eclipse/ditto/json/JsonFieldSelectorTrieTest.java b/json/src/test/java/org/eclipse/ditto/json/JsonFieldSelectorTrieTest.java
index 6efaf4c38c..aba3c90517 100644
--- a/json/src/test/java/org/eclipse/ditto/json/JsonFieldSelectorTrieTest.java
+++ b/json/src/test/java/org/eclipse/ditto/json/JsonFieldSelectorTrieTest.java
@@ -48,6 +48,36 @@ public void trieWithNonemptyPaths() {
         assertThat(getDescendantKeys(underTest, "c")).isEmpty();
     }
 
+    @Test
+    public void trieWithJsonObjectAndCertainFieldInSameJsonObject() {
+        // given
+        // a field selector containing both, a "field" inside an "object" and the "object" itself
+        final JsonFieldSelector fieldSelector = JsonFieldSelector.newInstance("object/field", "object");
+
+        // when
+        final JsonFieldSelectorTrie underTest = JsonFieldSelectorTrie.of(fieldSelector);
+
+        // then
+        assertThat(getDescendantKeys(underTest)).isEqualTo(keySetOf("object"));
+        // ensure that not only the "field" is contained, but the complete "object" instead:
+        assertThat(getDescendantKeys(underTest, "object")).isEmpty();
+    }
+
+    @Test
+    public void trieWithJsonObjectAndCertainFieldInSameJsonObjectOrderSwapped() {
+        // given
+        // a field selector containing both, a "field" inside an "object" and the "object" itself
+        final JsonFieldSelector fieldSelectorReverse = JsonFieldSelector.newInstance("object", "object/field");
+
+        // when
+        final JsonFieldSelectorTrie underTestReverse = JsonFieldSelectorTrie.of(fieldSelectorReverse);
+
+        // then
+        assertThat(getDescendantKeys(underTestReverse)).isEqualTo(keySetOf("object"));
+        // ensure that not only the "field" is contained, but the complete "object" instead:
+        assertThat(getDescendantKeys(underTestReverse, "object")).isEmpty();
+    }
+
     private static Set<JsonKey> keySetOf(final String... keyNames) {
         return Arrays.stream(keyNames).map(JsonKey::of).collect(Collectors.toSet());
     }