From 94c14273a74dd20e254bdf70c550391cb0856db9 Mon Sep 17 00:00:00 2001
From: Peter Kotula <peto.kotula@yahoo.com>
Date: Sat, 4 Nov 2023 20:14:32 +0100
Subject: [PATCH] json logger - null value for json attribute if value result
 is empty

---
 .../scala/zio/logging/JsonLogFormatSpec.scala | 28 +++++++++++++++++++
 .../zio/logging/internal/LogAppender.scala    |  4 +++
 2 files changed, 32 insertions(+)

diff --git a/core/jvm/src/test/scala/zio/logging/JsonLogFormatSpec.scala b/core/jvm/src/test/scala/zio/logging/JsonLogFormatSpec.scala
index 2ac697ada..1e68081bf 100644
--- a/core/jvm/src/test/scala/zio/logging/JsonLogFormatSpec.scala
+++ b/core/jvm/src/test/scala/zio/logging/JsonLogFormatSpec.scala
@@ -298,6 +298,34 @@ object JsonLogFormatSpec extends ZIOSpecDefault {
           val annEscaped = JsonEscape(nonJsonAnnotation)
           assertTrue(result == s"""{"json_annotation":$jsonAnnotation,"nonjson_annotation":"$annEscaped"}""")
         }
+      },
+      test("labeled empty spans") {
+        val format = label("spans", spans)
+        val result = format.toJsonLogger(
+          Trace.empty,
+          FiberId.None,
+          LogLevel.Info,
+          () => "",
+          Cause.empty,
+          FiberRefs.empty,
+          Nil,
+          Map.empty
+        )
+        assertTrue(result == s"""{"spans":null}""")
+      },
+      test("nested labeled empty spans and annotations") {
+        val format = label("data", label("line", line) + label("spans", spans) + label("annotations", allAnnotations))
+        val result = format.toJsonLogger(
+          Trace.empty,
+          FiberId.None,
+          LogLevel.Info,
+          () => "line",
+          Cause.empty,
+          FiberRefs.empty,
+          Nil,
+          Map.empty
+        )
+        assertTrue(result == s"""{"data":{"line":"line","spans":null,"annotations":null}}""")
       }
     )
   )
diff --git a/core/shared/src/main/scala/zio/logging/internal/LogAppender.scala b/core/shared/src/main/scala/zio/logging/internal/LogAppender.scala
index a1d13cc0d..0d271cac4 100644
--- a/core/shared/src/main/scala/zio/logging/internal/LogAppender.scala
+++ b/core/shared/src/main/scala/zio/logging/internal/LogAppender.scala
@@ -231,6 +231,10 @@ private[logging] object LogAppender {
         result.append("}")
       }
 
+      if (result.isEmpty) {
+        result.append("null")
+      }
+
       stack.pop()
       result
     }