From 2a196927a9c83c86fc9ba5e9908a757004eadb3e Mon Sep 17 00:00:00 2001
From: Andrea Di Cesare <andrea@softinstigate.com>
Date: Tue, 19 Dec 2023 11:11:39 +0100
Subject: [PATCH] :bug: Fix BsonUtils.toJson() for empty arrays

---
 .../src/main/java/org/restheart/utils/BsonUtils.java   |  8 ++++----
 .../test/java/org/restheart/utils/BsonUtilsTest.java   | 10 ++++++++++
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/commons/src/main/java/org/restheart/utils/BsonUtils.java b/commons/src/main/java/org/restheart/utils/BsonUtils.java
index 6c28cbe00..9b01e2c21 100644
--- a/commons/src/main/java/org/restheart/utils/BsonUtils.java
+++ b/commons/src/main/java/org/restheart/utils/BsonUtils.java
@@ -672,10 +672,8 @@ public static String toJson(BsonValue bson) {
 
     /**
      * @param bson either a BsonDocument or a BsonArray
-     * @param mode
+     * @param mode the JsonMode
      * @return the minified string representation of the bson value
-     * @throws IllegalArgumentException if bson is not a BsonDocument or a
-     * BsonArray
      */
     public static String toJson(BsonValue bson, JsonMode mode) {
         if (bson == null) {
@@ -700,7 +698,9 @@ public static String toJson(BsonValue bson, JsonMode mode) {
 
             sb.append("[");
             bson.asArray().stream().map(e -> toJson(e)).map(e -> minify(e)).forEach(e -> sb.append(e).append(","));
-            sb.deleteCharAt(sb.length()-1); // remove last comma
+            if (sb.length() > 1) {
+                sb.deleteCharAt(sb.length()-1); // remove last comma
+            }
             sb.append("]");
 
             return sb.toString();
diff --git a/commons/src/test/java/org/restheart/utils/BsonUtilsTest.java b/commons/src/test/java/org/restheart/utils/BsonUtilsTest.java
index 1a9600f7a..3bbad2077 100644
--- a/commons/src/test/java/org/restheart/utils/BsonUtilsTest.java
+++ b/commons/src/test/java/org/restheart/utils/BsonUtilsTest.java
@@ -1000,4 +1000,14 @@ public void testXPathGet() {
         assertFalse(BsonUtils.get(doc, "array[100].idx").isPresent());
         assertFalse(BsonUtils.get(doc, "not.exists").isPresent());
     }
+
+
+    @Test
+    public void testToJsonEmptyArray() {
+        var expected = "[]";
+
+        var actual = BsonUtils.toJson(new BsonArray());
+
+        assertEquals(expected, actual);
+    }
 }