AK: JsonParser improvements

- Parsing invalid JSON no longer asserts
    Instead of asserting when coming across malformed JSON,
    JsonParser::parse now returns an Optional<JsonValue>.
- Disallow trailing commas in JSON objects and arrays
- No longer parse 'undefined', as that is a purely JS thing
- No longer allow non-whitespace after anything consumed by the initial
  parse() call. Examples of things that were valid and no longer are:
    - undefineddfz
    - {"foo": 1}abcd
    - [1,2,3]4
- JsonObject.for_each_member now iterates in original insertion order

Userland/arp.cpp

@@ -39,8 +39,9 @@ int main()
 
     printf("Address          HWaddress\n");
     auto file_contents = file->read_all();
-    auto json = JsonValue::from_string(file_contents).as_array();
-    json.for_each([](auto& value) {
+    auto json = JsonValue::from_string(file_contents);
+    ASSERT(json.has_value());
+    json.value().as_array().for_each([](auto& value) {
         auto if_object = value.as_object();
 
         auto ip_address = if_object.get("ip_address").to_string();

Userland/df.cpp

@@ -86,7 +86,9 @@ int main(int argc, char** argv)
     }
 
     auto file_contents = file->read_all();
-    auto json = JsonValue::from_string(file_contents).as_array();
+    auto json_result = JsonValue::from_string(file_contents);
+    ASSERT(json_result.has_value());
+    auto json = json_result.value().as_array();
     json.for_each([](auto& value) {
         auto fs_object = value.as_object();
         auto fs = fs_object.get("class_name").to_string();

Userland/gron.cpp

@@ -74,6 +74,7 @@ int main(int argc, char** argv)
 
     auto file_contents = file->read_all();
     auto json = JsonValue::from_string(file_contents);
+    ASSERT(json.has_value());
 
     if (use_color) {
         color_name = "\033[33;1m";
@@ -86,7 +87,7 @@ int main(int argc, char** argv)
     }
 
     Vector<String> trail;
-    print("json", json, trail);
+    print("json", json.value(), trail);
     return 0;
 }
 
@@ -116,7 +117,6 @@ static void print(const String& name, const JsonValue& value, Vector<String>& tr
     }
     switch (value.type()) {
     case JsonValue::Type::Null:
-    case JsonValue::Type::Undefined:
         printf("%s", color_null);
         break;
     case JsonValue::Type::Bool:

Userland/ifconfig.cpp

@@ -72,8 +72,9 @@ int main(int argc, char** argv)
         }
 
         auto file_contents = file->read_all();
-        auto json = JsonValue::from_string(file_contents).as_array();
-        json.for_each([](auto& value) {
+        auto json = JsonValue::from_string(file_contents);
+        ASSERT(json.has_value());
+        json.value().as_array().for_each([](auto& value) {
             auto if_object = value.as_object();
 
             auto name = if_object.get("name").to_string();

Userland/jp.cpp

@@ -63,8 +63,9 @@ int main(int argc, char** argv)
 
     auto file_contents = file->read_all();
     auto json = JsonValue::from_string(file_contents);
+    ASSERT(json.has_value());
 
-    print(json);
+    print(json.value());
     printf("\n");
 
     return 0;
@@ -101,7 +102,7 @@ void print(const JsonValue& value, int indent)
         printf("\033[35;1m");
     else if (value.is_bool())
         printf("\033[32;1m");
-    else if (value.is_null() || value.is_undefined())
+    else if (value.is_null())
         printf("\033[34;1m");
     if (value.is_string())
         putchar('"');

Userland/lsirq.cpp

@@ -60,8 +60,9 @@ int main(int argc, char** argv)
 
     printf("%4s  %-10s\n", " ", "CPU0");
     auto file_contents = proc_interrupts->read_all();
-    auto json = JsonValue::from_string(file_contents).as_array();
-    json.for_each([](auto& value) {
+    auto json = JsonValue::from_string(file_contents);
+    ASSERT(json.has_value());
+    json.value().as_array().for_each([](auto& value) {
         auto handler = value.as_object();
         auto purpose = handler.get("purpose").to_string();
         auto interrupt = handler.get("interrupt_line").to_string();

Userland/lspci.cpp

@@ -69,8 +69,9 @@ int main(int argc, char** argv)
     }
 
     auto file_contents = proc_pci->read_all();
-    auto json = JsonValue::from_string(file_contents).as_array();
-    json.for_each([db](auto& value) {
+    auto json = JsonValue::from_string(file_contents);
+    ASSERT(json.has_value());
+    json.value().as_array().for_each([db](auto& value) {
         auto dev = value.as_object();
         auto seg = dev.get("seg").to_u32();
         auto bus = dev.get("bus").to_u32();

Userland/mount.cpp

@@ -149,9 +149,10 @@ bool print_mounts()
     }
 
     auto content = df->read_all();
-    auto json = JsonValue::from_string(content).as_array();
+    auto json = JsonValue::from_string(content);
+    ASSERT(json.has_value());
 
-    json.for_each([](auto& value) {
+    json.value().as_array().for_each([](auto& value) {
         auto fs_object = value.as_object();
         auto class_name = fs_object.get("class_name").to_string();
         auto mount_point = fs_object.get("mount_point").to_string();