Fix json null (#5202)

Author: acquamarin

dataset/json-misc/null_in_struct.json

@@ -0,0 +1,15 @@
+{
+  "accountContacts": [
+    {
+      "objectType": "contact",
+      "schemaVersion": null,
+      "contactIdentifier": "320864",
+      "contactNamespace": "56127",
+      "contactDetail": {
+        "fullname": "Renee Luke",
+        "email": "[email protected]",
+        "phone": "(678) 252-4828 - Direct"
+      }
+    }
+  ]
+}

dataset/json-misc/null_in_struct2.json

@@ -0,0 +1,15 @@
+{
+  "accountContacts": [
+    {
+      "objectType": "contact",
+      "schemaVersion": "135",
+      "contactIdentifier": "320864",
+      "contactNamespace": null,
+      "contactDetail": {
+        "fullname": "Renee Luke",
+        "email": "[email protected]",
+        "phone": "(678) 252-4828 - Direct"
+      }
+    }
+  ]
+}

extension/json/src/functions/table_functions/json_scan.cpp

@@ -778,7 +778,7 @@ static JsonScanFormat autoDetect(main::ClientContext* context, const std::string
     }
 
     for (auto& type : types) {
-        LogicalTypeUtils::purgeAny(type, LogicalType::STRING());
+        type = LogicalTypeUtils::purgeAny(type, LogicalType::STRING());
     }
     return sharedState.jsonReader->getFormat();
 }

extension/json/test/scan_json.test

@@ -157,6 +157,12 @@ Unable to find primary key value 6.|${KUZU_ROOT_DIRECTORY}/dataset/json-error/in
 8246337208329|2012-07-20 23:08:15.828|31.13.184.200|Firefox|About George Frideric Handel, ful with hisAbout Erwin Rommel, mandy. As onAbout|79
 8246337208330|2012-07-20 06:31:37.85|62.100.246.118|Internet Explorer|good|4
 8246337208331|2012-07-21 03:07:22.319|46.30.7.107|Firefox|no|2
+-STATEMENT LOAD FROM '${KUZU_ROOT_DIRECTORY}/dataset/json-misc/null_in_struct.json' RETURN *;
+---- 1
+[{objectType: contact, schemaVersion: , contactIdentifier: 320864, contactNamespace: 56127, contactDetail: {fullname: Renee Luke, email: [email protected], phone: (678) 252-4828 - Direct}}]
+-STATEMENT LOAD FROM '${KUZU_ROOT_DIRECTORY}/dataset/json-misc/null_in_struct2.json' RETURN *;
+---- 1
+[{objectType: contact, schemaVersion: 135, contactIdentifier: 320864, contactNamespace: , contactDetail: {fullname: Renee Luke, email: [email protected], phone: (678) 252-4828 - Direct}}]
 
 -CASE InstallOfficialExtension
 -STATEMENT INSTALL json FROM 'http://localhost/extension/repo/'