Fixes the issue of losing the array if an empty forceList element or a tag is in the middle or the end

src/main/java/org/json/XML.java

@@ -391,7 +391,7 @@ public class XML {
                             context.append(tagName, JSONObject.NULL);
                         } else if (jsonObject.length() > 0) {
                             context.append(tagName, jsonObject);
-                        } else {
+                        } else if(context.isEmpty() && (context.opt(tagName) == null || !(context.get(tagName) instanceof JSONArray))) { //avoids resetting the array in case of an empty tag in the middle or end
                             context.put(tagName, new JSONArray());
                         }
                     } else {
@@ -451,7 +451,10 @@ public class XML {
                                 if (config.getForceList().contains(tagName)) {
                                     // Force the value to be an array
                                     if (jsonObject.length() == 0) {
-                                        context.put(tagName, new JSONArray());
+                                        //avoids resetting the array in case of an empty element in the middle or end
+                                        if(context.length()==0 && context.opt(tagName) == null || !(context.get(tagName) instanceof JSONArray)) {
+                                            context.put(tagName, new JSONArray());
+                                        }
                                     } else if (jsonObject.length() == 1
                                             && jsonObject.opt(config.getcDataTagName()) != null) {
                                         context.append(tagName, jsonObject.opt(config.getcDataTagName()));

src/test/java/org/json/junit/XMLConfigurationTest.java

@@ -1144,6 +1144,114 @@ public class XMLConfigurationTest {
         Util.compareActualVsExpectedJsonObjects(jsonObject, expetedJsonObject);
     }
 
+    @Test
+    public void testForceListWithLastElementAsEmptyTag(){
+        final String originalXml = "<root><id>1</id><id/></root>";
+        final String expectedJsonString = "{\"root\":{\"id\":[1]}}";
+
+        HashSet<String> forceListCandidates = new HashSet<>();
+        forceListCandidates.add("id");
+        final JSONObject json = XML.toJSONObject(originalXml,
+                new XMLParserConfiguration()
+                        .withKeepStrings(false)
+                        .withcDataTagName("content")
+                        .withForceList(forceListCandidates)
+                        .withConvertNilAttributeToNull(true));
+        assertEquals(expectedJsonString, json.toString());
+    }
+
+    @Test
+    public void testForceListWithFirstElementAsEmptyTag(){
+        final String originalXml = "<root><id/><id>1</id></root>";
+        final String expectedJsonString = "{\"root\":{\"id\":[1]}}";
+
+        HashSet<String> forceListCandidates = new HashSet<>();
+        forceListCandidates.add("id");
+        final JSONObject json = XML.toJSONObject(originalXml,
+                new XMLParserConfiguration()
+                        .withKeepStrings(false)
+                        .withcDataTagName("content")
+                        .withForceList(forceListCandidates)
+                        .withConvertNilAttributeToNull(true));
+        assertEquals(expectedJsonString, json.toString());
+    }
+
+    @Test
+    public void testForceListWithMiddleElementAsEmptyTag(){
+        final String originalXml = "<root><id>1</id><id/><id>2</id></root>";
+        final String expectedJsonString = "{\"root\":{\"id\":[1,2]}}";
+
+        HashSet<String> forceListCandidates = new HashSet<>();
+        forceListCandidates.add("id");
+        final JSONObject json = XML.toJSONObject(originalXml,
+                new XMLParserConfiguration()
+                        .withKeepStrings(false)
+                        .withcDataTagName("content")
+                        .withForceList(forceListCandidates)
+                        .withConvertNilAttributeToNull(true));
+        assertEquals(expectedJsonString, json.toString());
+    }
+
+    @Test
+    public void testForceListWithLastElementAsEmpty(){
+        final String originalXml = "<root><id>1</id><id></id></root>";
+        final String expectedJsonString = "{\"root\":{\"id\":[1]}}";
+
+        HashSet<String> forceListCandidates = new HashSet<>();
+        forceListCandidates.add("id");
+        final JSONObject json = XML.toJSONObject(originalXml,
+                new XMLParserConfiguration()
+                        .withKeepStrings(false)
+                        .withForceList(forceListCandidates)
+                        .withConvertNilAttributeToNull(true));
+        assertEquals(expectedJsonString, json.toString());
+    }
+
+    @Test
+    public void testForceListWithFirstElementAsEmpty(){
+        final String originalXml = "<root><id></id><id>1</id></root>";
+        final String expectedJsonString = "{\"root\":{\"id\":[1]}}";
+
+        HashSet<String> forceListCandidates = new HashSet<>();
+        forceListCandidates.add("id");
+        final JSONObject json = XML.toJSONObject(originalXml,
+                new XMLParserConfiguration()
+                        .withKeepStrings(false)
+                        .withForceList(forceListCandidates)
+                        .withConvertNilAttributeToNull(true));
+        assertEquals(expectedJsonString, json.toString());
+    }
+
+    @Test
+    public void testForceListWithMiddleElementAsEmpty(){
+        final String originalXml = "<root><id>1</id><id></id><id>2</id></root>";
+        final String expectedJsonString = "{\"root\":{\"id\":[1,2]}}";
+
+        HashSet<String> forceListCandidates = new HashSet<>();
+        forceListCandidates.add("id");
+        final JSONObject json = XML.toJSONObject(originalXml,
+                new XMLParserConfiguration()
+                        .withKeepStrings(false)
+                        .withForceList(forceListCandidates)
+                        .withConvertNilAttributeToNull(true));
+        assertEquals(expectedJsonString, json.toString());
+    }
+
+    @Test
+    public void testForceListEmptyAndEmptyTagsMixed(){
+        final String originalXml = "<root><id></id><id/><id>1</id><id/><id></id><id>2</id></root>";
+        final String expectedJsonString = "{\"root\":{\"id\":[1,2]}}";
+
+        HashSet<String> forceListCandidates = new HashSet<>();
+        forceListCandidates.add("id");
+        final JSONObject json = XML.toJSONObject(originalXml,
+                new XMLParserConfiguration()
+                        .withKeepStrings(false)
+                        .withForceList(forceListCandidates)
+                        .withConvertNilAttributeToNull(true));
+        assertEquals(expectedJsonString, json.toString());
+    }
+
     @Test
     public void testMaxNestingDepthIsSet() {
         XMLParserConfiguration xmlParserConfiguration = XMLParserConfiguration.ORIGINAL;