From a409b832facf87b7623b5e649aec4ef4f6880161 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Thu, 16 Dec 2021 21:52:20 +0100
Subject: [PATCH] AK: Make JsonValue::from_string("") return a null JsonValue

This unbreaks the /var/run/utmp system which starts out as an empty
string, and is then turned into an object by the first update.

This isn't necessarily the best way for this to work, but it's how
it used to work, so this just fixes the regression for now.
---
 AK/JsonValue.cpp      | 2 ++
 Tests/AK/TestJSON.cpp | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/AK/JsonValue.cpp b/AK/JsonValue.cpp
index 074d7f1819..a1bc94ce55 100644
--- a/AK/JsonValue.cpp
+++ b/AK/JsonValue.cpp
@@ -230,6 +230,8 @@ void JsonValue::clear()
 #ifndef KERNEL
 ErrorOr<JsonValue> JsonValue::from_string(StringView input)
 {
+    if (input.is_empty())
+        return JsonValue();
     return JsonParser(input).parse();
 }
 #endif
diff --git a/Tests/AK/TestJSON.cpp b/Tests/AK/TestJSON.cpp
index aa1f8139a9..7f0cbab296 100644
--- a/Tests/AK/TestJSON.cpp
+++ b/Tests/AK/TestJSON.cpp
@@ -122,3 +122,9 @@ TEST_CASE(json_u64_roundtrip)
     EXPECT_EQ_FORCE(value.is_error(), false);
     EXPECT_EQ(value.value().as_u64(), big_value);
 }
+
+TEST_CASE(json_parse_empty_string)
+{
+    auto value = JsonValue::from_string("");
+    EXPECT_EQ(value.value().is_null(), true);
+}